Download Microbiology

Microbiology
Introduction



This is the study of viruses, bacteria, fungi, and parasites.
Usually microscopes are required. The human vision can only see about 40
microns with the unaided eye.
o Viruses- 0.03-0.2 microns
o Bacteria- 0.1-10 microns
o Microscopic protozoa, fungi 4-40 microns
o Parasites vary considerably. Ectoparasites are a term for fleas, lice, mites,
and ticks.
Prokaryotes vs. Eukaryotes
o Prokaryotes
 These are small, and morphologically simple. The vast majority of
the bacteria are free-living organisms with typical prokaryote
features.
 Prokaryote literally means “before nucleus,” so there is no
membrane delimited nucleus, no organelles, and mitosis does not
occur. Instead, they divide by binary fission. Some are obligate
parasites, and need to live within another.
 Classes
 Bacteria
o The prototypical bacteria may be the simplest form
of life, but they are still very complex and capable
of carrying on many different tasks. Not all bacteria
have all of these structures
 Cyanobacteria
 Structures
 Instead, they have a single circle of double stranded DNA
located in an irregularly shaped region called the nucleoid
(aka nucleus body, chromatin body, or nuclear region). The
ribosomes are also smaller (70s). No compartmentalization
(organelles) is present. Therefore there is no specialization
of function.
 Cytoplasmic Matrix
o This is present between the plasma membrane and
nucleoid region. It is often packed with ribosomes.
 30S + 50S = 70S
 S = Svedberg Unit
o Inclusion bodies are sometimes found, as well as
dispersed glycogen or poly B hydroxybutyrate
(PHB) granules as a form at carbon storage.
 Nucleoid Region
o No membrane-bound nucleus, but there is a region
with slight function. Nucleoid regions are actually
structures consisting of DNA, some RNA, and some
protein. Area of DNA replication/transcription.
o Eukaryotes are the opposite
 Eukaryotes include plants, animals, multicellular algae, fungi, and
protozoa. These are morphologically complex cells, containing
organelles such as mitochondria, lysosomes and larger (80s)
ribosomes. These are usually larger than prokaryotes.
 Nucleus
 Eukaryotes have a true membrane-enclosed nucleus with
two or more chromosomes and use a mitotic apparatus to
ensure equal allocation of the chromosomes to progeny
cells.
 Organelles
 Ribosomes
o 40S + 60S = 80S
 Mitochondria
o Endosymbient Hypothesis
 Mitochondria and chloroplasts were once
prokaryotes. They are the same size and
have their own DNA, and look similar.
 Lysosomes
o Summary
Bacteria
Anatomy


Bacteria are classified under the kingdom Monera, and are further divided
phylogenically on the basis of size, shape, and cell arrangement.
o Most bacteria have one of three characteristic shapes.
 Coccus- round
 Bacillus- rods
 Spirillum- spiral
Cell wall/ envelope
o Along with the cytoskeleton, this functions to define the cellular shape and
protect the cell from osmotic shock/lysis.
o The cell wall is the outmost component common to all bacteria except
Mycoplasma which is bound by a cell membrane. This is a multilayer
structure located external to the cytoplasmic membrane. It is composed of
an inner layer of peptidoglycan surrounded by an outer membrane that
varies in thickness and chemical composition depending upon the bacterial
type (Gram reaction).
 Peptidoglycan (Murein)
 This is a polymer composed of identical subunits.
o Sugar derivatives consist of alternating Nacetylglucosamine (NAG) and N-acetylmuramic
acids (NAM) are linked together by peptides.
o Amino acids D-glutamic acid, D-alanine, and mesodiaminopimelic acid are used for cross-linking for
strength
 The synthesis of peptidoglycan chains and crosslinking
pathways are important target sites of action for several
classes of antibiotics.
 The first step in identification of bacteria is the gram stain. This
was discovered by Christian Gram in 1884. This test differentiates


between gram positive and gram negative organisms. There are
fundamental differences between the two, so they are treated
differently. The major difference is in the cell wall composition.
Gram Positive cell envelope
 This is a relatively simple structure.
 The homogenous thick layer of peptidoglycan keeps the
crystal violet stain from washing away during staining.
These bacteria stain blue or violet.
 This also contains lipoteichoic and teichoic acids, which
are polymers of glycerol or ribitol joined by phosphate
groups.
 Gram + cells are more likely to excrete enzymes involved
in nutrient acquisition, due to the difference in
permeability, i.e., exoenzymes. They partially digest
materials to move it through the cell, which occurs
externally.
Gram Negative envelope
 This is a much more complex cell than gram positive.
 There is only a thin layer of peptidoglycan, and there are no
teichoic acids. This means that it stains pink or red, because
the thin peptidoglycan layer loses the violet dye during
staining.
 The periplasmic space contains many proteins involved in
nutrient acquisition (enzymes).
o The outer membrane contains proteins.
 Among them are porin proteins which allow
certain molecules (usually nutrients) to pass
through the outer membrane, preventing
others. It is a selective barrier.
 Lipopolysaccharides (LPS) consist of lipid
A, core polysaccharide, and an O side chain.
 Lipid A is a phospholipid that serves
as an endotoxin responsible for many
symptoms due to gram negative
infections
 The O chain serves as an antigenic
marker and can be rapidly switched
by the bacteria to avoid host
defenses.
o Summary
Normal Flora


There is a normal colonization of bacteria on the body, proving that not all
bacteria are pathogenic, which are microbes that are capable of infecting or
parasitizing a normal host, producing a diseased state. Some are actually
protective and beneficial. The body surface supports the growth of a variety of
bacteria and fungi. The normal flora populates extensively many areas of the body
except for the internal organs.
The members of the normal flora play a role both in the maintenance of health
and in the causation of disease in three significant ways.
o They can cause disease in immunocompromised and debilitated
individuals. Although these organisms are nonpathogens in their usual
anatomical location, they can be pathogens in others parts of the body.
o They constitute a protective host defense mechanism. The nonpathogenic
resident bacteria occupy ecological niches, and so pathogens have
difficulty in multiplying efficiently. If the normal flora is suppressed,
pathogens may grow and cause disease.
o They may serve a nutritional function. The intestinal bacteria produce
several B vitamins and vitamin K. Poorly nourished people who are
treated with oral antibiotics can suffer vitamin deficiencies as a result of
the reduction in the normal flora. However, since germ-free animals are
well nourished, the normal flora is not essential for proper function.


Relationships between normal flora and host
o Symbiosis- the living together or close association of two dissimilar
organisms.
o Commensalisms- type of symbiosis in which one organism gains from the
association and the other is unharmed. E.g., Corynebacterium xerosis that
inhabits the surface of the eye.
o Mutualism- type of symbiosis in which both organisms gain from the
association and are unable to survive without it. E.g., E. Coli of the
intestines.
o Parasitism- type of symbiosis in which one organism adversely affects the
other but cannot live without it.
Medically Important Members of the Normal Flora
Growth and Metabolism

Microbial Nutrition
o Microorganisms share some of the same basic requirements for nutrients
that most other living organisms have, but on a simpler level.
 They require appropriate forms of various elements such as C, H,
O, N, P, and S.
 They generate their own amino acids
o Source of Carbon
 Autotrophs can fix CO2 as the sole carbon source.
 Heterotrophs require more complex forms of carbon.
 The usual source is from other organisms, which is mainly
organic. This term is fastidious. i.e., H. flu requires S.
aureus
 Prototrophs have some nutritional requirements as most members
of the species, as determined via consensus. These have a normal
or wild-type phenotype. No mutations are required to change.

Auxotrophs lack the ability to synthesize an essential component,
so that component must be obtained from its surroundings. This is
due to a mutation in the gene(s) encoding enzyme(s) to do a job.
 Photoautotrophs use light as an energy source and carry out
photosynthesis. This is rare.
 Chemoautotrophs fix CO2 without photosynthesis. This requires
large amounts of energy and is found only in extreme
environments, such as volcanoes, etc.
o Source of Oxygen: Anaerobic vs. Aerobic
 Almost all higher organisms are completely dependent on
atmospheric oxygen for growth. Oxygen serves as the terminal
electron acceptor for the electron transport chain in aerobic
respiration (Kreb’s Cycle). In addition, aerobic eukaryotes employ
oxygen in the synthesis of sterols and unsaturated fatty acids.
When oxygen is utilized (i.e., reduced) in aerobic respiration,
hydrogen peroxide and free radical superoxide are produced. Both
products are powerful oxidizing agents which destroy cellular
constituents, therefore they are extremely toxic. A microorganism
must be able to protect itself against such oxygen products or it
will be killed. Obligate aerobes and facultative anaerobes usually
contain the enzymes superoxide dismutase and catalase, which
catalyze the destruction of superoxide radical and hydrogen
peroxide, respectively.
 Obligate aerobes require oxygen to grow, because their ATPgenerating system is dependent on oxygen as the electron acceptor.
An example would be M. tuberculosis.
 Facultative anaerobes (facultatives) utilize oxygen to generate
energy for respiration if it is present, but they can use the
fermentation pathway to synthesize ATP in the absence of
sufficient oxygen. An example would be E. Coli.
 Obligate anaerobes cannot grow in the presence of oxygen,
because they lack either superoxide dismutase or catalase, or both.
Obligate anaerobes vary in their response to oxygen exposure.
Some can survive but are not able to grow, whereas others are
killed rapidly. The final electron acceptor is usually an inorganic
substance, producing a variable amount of ATP. An example is
Clostridium tetani.
 Microaeophiles require lower amounts of oxygen.
o Uptake of nutrients into cells.
 Passive diffusion
 Facilitated Diffusion
 Active transport
 This is probably the most important form of movement for
prokaryotes.
 There is not necessarily just one transport system per
nutrient. Some are shared and some have a backup.

Sometimes bacteria can still survive without a transport
mechanism due to backup
 Group translocation
 Here molecules are transported into cells while they are
being chemically modified. Often sugars are transported
and phosphorylated simultaneously.
Microbial Growth
o Life Cycle
 Bacteria reproduce by binary fission, a process by which one
parent cell divides to form two progeny cells, undergoing
exponential growth (2n). The doubling (generation) time ranges
from 20 min for E. Coli to more than 24 hours for M. tuberculosis.
 Generation of doubling time
 This varies considerably among microorganisms and upon
growth conditions
 It typically doubles once every 20 minutes (ex. E. Coli), but
can be as quickly as once every 10 minutes.
 The average for aerobes is about once every hour, and once
every few hours for anaerobes. Facultative bacteria double
once every 10-15 minutes in aerobic conditions or once
every 1-3 hours in anaerobic conditions.
o Growth is an increase in amount of cellular constituents leading to cell
division and eventually an increase in size of population.
 I (initiation) period
 Cell elongates in preparation for fission.
 C period
 Bacterial chromosome replicates. Proteins needed for
division are synthesized.
 D (division) period
 Plasma membrane near center of cell pinches inward. Cell
wall thickens and grows inward at this same point, forming
the transverse wall/septum.
 The bacteria increase in size and volume. The cells are less viable
if they grow and do not split. A certain class of antibiotics stops the
splitting process. The bacteria grow without splitting and die.
o Growth can be determined by counting number of bacteria directly or
indirectly by the plating of serial dilutions


A solution is diluted until there are about 30-300 colonies on a
dish. The number of bacteria are counted here and then counted
back to find the number in the original sample.
This is accurate, but it takes longer than the direct method where
one needs to allow bacteria to grow to directly count. Cell turbidity
(density) can also be measured with scales. The problem with these
methods is that one cannot differentiate between alive and dead
cells.
o Growth curve

Four distinct phases
 Lag phase
o This is the division mode where cells synthesize
new components in preparation for division. This is
a time of vigorous metabolic activity, but cells do
not divide. Cells grow in size and are acclimating to
the new environment.
 Exponential (log) phase
o Bacteria grow and divide at the maximal rate under
the given conditions. They show visible
characteristics of shape, color, density, and
groupings of colonies. Divisions are occurring more
than death.
o Drugs can be most effective at this time.
 Stationary Phase
o Here there are about ~109-1010 bacterial cells per
ml. The rate of division is equal to the rate of death.
This is due to the limitations of natural resource and
the accumulation of toxic waste. This can be
overcome by using a chemostat.
 Death phase
o This is a decline in the population, because the rate
of division is less than that of death. Nutrients are
depleted and the waste products become toxic.
o With the introduction of new media, it death phase
would lag, and the entire growth curve would then
start over.

Microbial Energetics
o Catabolism
 Large, complex molecules are broken down into smaller, simpler
molecules with the release of energy. Some energy is captured and
used for other processes within the cell, while the rest is lost as
heat. Glucose is the preferred energy source. This is about 40%
efficient, meaning that 40% of the ATP is retained, and the rest is
lost.
 Processes
 Glycolysis
 Tricarboxylic acid (Krebs) cycle
 Electron transport and oxidative phosphorylation
 Overall, there is a theoretical yield of 34-38 ATP/glucose, but not
all will go through. Some is pulled from the TCA cycle, making
the average about 20-25/ glucose.
 Fermentation
 In absence of oxygen, NADH needs to be converted back
to NAD+ for glycolysis. Fermentators use pyruvate or a
form of pyruvate as the electron acceptor and/or donor.
This gives rise to many different fermentation products.
Many are
important
Microbial Genetics


Introduction
o This is the driving force of microbial diversity. It can lead to increased
antibiotic resistance, increased pathogenicity, etc.
o The genetic material of a typical bacterium consists of a single circular
chromosome. This is a haploid of about 2x109 Daltons and approximately
2000 genes.
Genetic Recombination
o Genetic recombination is process by which genetic elements from two
separate genomes are brought together into one unit. This is important,
because it allows a strong selection to show up in a population in a short
amount of time. From a medical viewpoint, this is the most important
consequence of DNA transfer
o Griffith’s Experiment in the early 1900s discovered that nucleic acid is the
genetic material.
o To create new genotypes, have to have genetically distinct DNA
molecules present in the same cell.

o Three types of recombination
 General recombination
 This is the most common. It requires regions of homology
between two genetic elements (~40 base pairs, 75%
identical), as well as a RecA protein (Rec = recombinase).
 Site-specific recombination
 No homology/proteins are required. This is important for
the integration of bacteriophage genomes into bacterial
chromosomes during lysogeny.
 Conjugative recombination
 This is important for the movement of certain transposons.
The transfer of genetic information from one prokaryotic bacterium to another can
occur in 3 methods: conjugation, transduction, and transformation.
o Conjugation
 Conjugation, or “bacterial sex,” is accomplished by temporary,
direct, physical contact between two bacteria. The F (fertility)
plasmid is transferred by itself or with a portion of the bacterial
DNA in cells from the donor to the recipient via a sex pilus
(conjugation tube). The F plasmid is integrated into the bacterial
DNA and can recombine into the recipient’s DNA to become a
stable component of the recipient’s genetic make-up.
 Plasmids
 These are autonomous (replicate separate from
chromosome), circular, double-stranded DNA molecules
that exist and replicate extrachromosomally. They are
generally small (usually less than 100kB), except for
“megaplasmids.”
 Usually they are not required for the normal growth of
bacteria, but they often have genes which give bacteria
harboring them a selective advantage under some
conditions.
 The first plasmids discovered were the Ab-resistant
plasmids, which is a big problem, because they cause
antibiotic resistance.
 Examples of genes carried by plasmids include those that
are responsible for producing toxins, antibiotic resistance,
conjugation control/capability, compound degradation (ex.
cleaning oil spills), and virulence factor production.


Studies indicate that many bacteria are of the same species
and only differ in their complement of plasmids.
o Bacillus cereus- soil living bacterium and
occasional food poisoning culprit
o Bacillus thuringicrisis- widely used insect
biocontrol
o Bacillis anthracis- life threatening biological
warfare agent.
Transfer of the Plasmid
 The donor possesses the conjugative plasmid. It expresses a
sexual pili, which initiates contact with recipient. Cell to
cell contact is made, and then the DNA transfer occurs.

This is seen with F-plasmids, most commonly. The donor is
termed either F+ or male. The recipient is either F- or
female. These together make 2F+, meaning that both
bacteria now have the plasmid.

Incorporation of the Plasmid

Possible outcomes
o An F plasmid can integrate into a chromosome at
low frequencies.
o An Hfr (high frequency recombinant) must be
transferred quickly (about 1 hour for the entire
chromosome), but there are many disruptions. This
could lead to a partial transfer. This is transferred
the same as normal F.
 Hfr can go back to F+ (sometimes) with
excision.
o Transfer depends upon site and orientation of
integration.
o Sometimes F plasmid will excise from chromosome
and pick up chromosomal genes  F’ (F’
conjugation leads to increased frequency transfer of
these chromosomal genes)
 F’ = irregular excision.
o Genetic Transformation
 This is the transfer of a naked molecule of DNA from one cell to
another. Example of this include mature, dying bacteria releasing
their DNA, which is taken up by recipient cells, as well as
laboratory investigators extracting DNA from one type of bacteria
and introducing it into genetically different bacteria.


In general, only competent strains are transformable, and
only during certain stages of growth.
Possible fates of DNA

Proteins are the mediators controlling why certain bacteria
are transformed and others are not.
o
o These are expressed at mid/late log phase and hold
DNA, moving them into bacteria.
o Without proteins, bacteria are non-transformable
with natural conditions.
 New DNA may or may not be expressed.
Genetic Transduction
 This is the transfer of bacterial DNA by means of a bacteriophage
or a bacterial virus injection.
 Some lytic, lysogenic, or versatile (“temperate”),
depending on the condition of environment and host.
 Lytic vs. lysogenic cycles


The lytic cycle occurs when the environment is not healthy.
This leads to the destruction of the bacteria.
The lysogenic cycle occurs if the host is healthy, has
nutrients, etc. This leads to integration.

Generalized transduction




The generalized type of transduction occurs when random
fragments of partially degraded bacterial chromosomal
DNA are packaged into viral capsids and transferred to
another bacterium by adsorption and penetration at low, but
identical frequencies. This is either lytic or temperate.
The host genes come from virtually any portion of the host
genome and are transferred via the defective phage particle.
During the lytic cycle, the host DNA is often broken down
to viral genome-sized pieces. Some pieces (defective viral
particles) are mistakenly incorporated inside virus particles.
They act like normal phage particles, but they cannot
continue the lytic cycle.
On the other hand, foreign DNA can be introduced into the
recipient cell. Recombination may incorporate DNA into
the genome.

Specialized transduction




Specialized transduction occurs when a phage leaves the
host chromosome and takes a portion of the bacterial
chromosome next to the site of integration with it because
excision is carried out improperly.
Normally in induction, a phage excises precisely as a viral
unit. Imprecise excision can pick up bacterial genes
adjacent to the integration site while leaving behind viral
genes, but this is rare.
Here, certain phages are integrated into the host genome at
specific sites. This is called site-specific recombination.
Certain genes transfer at high or low frequencies (or both).
This only occurs with a temperate phage that must be able
to undergo lysogenic and lytic cycles.


o Transposition
 This is the process by which genes move from one place to another
on a genome. It was originally identified by Barbara McClintock
(Nobel prize in 1983) and her work with maize (different colored
kernels). This is a rare event (> 105–107 per generation).
 It is independent of RecA proteins.
 Insertion sequences (IS elements)
 These are short, specific segments of DNA which have the
ability to move to another site on the genome as discrete
units. This requires the action of the transposase gene. This
is located in the insertion sequence and catalyzes the
transposition.
 Transposons
 These are 2-15 genetic composites of movable elements
containing paired IS elements flanking genetic regions.
o Antibiotic resistance genes are often flanked.
Therefore, these are involved in the movement of
antibiotic resistance genes from one bacteria to
another. These are the easiest to identify.
Eukaryotes replicate via sexual reproduction
Endospore Formation
o These are highly resistant structures formed in response to adverse
conditions as a part of the natural life cycle of two genera of medically
important Gram + rods: the genus Bacillus and Clostridium.
o Spore formation (sporogenesis) occurs in normal vegetative cells when
nutrients, such as carbon and nitrogen, are depleted or there are other
environmental stresses which would threaten the normal cell. The spore
forms inside the cell and contains bacterial DNA, an accumulation of
dipicolinic acid, calcium, and protein.
o Once formed, the spore has no metabolic cavity and can remain dormant
indefinitely. Spores are resistant to heat, dehydration, UV radiation,
dessication, and chemical disinfectants. Upon exposure to water and the
appropriate nutrients, specific enzymes degrade the coat, water and
nutrients enter, and the germination into a metabolizing, reproducing
bacterial cell occurs. Germination (the breaking of a spore’s dormant
state) results in a loss of resistance to heat and other stresses, a loss in
refractivity, a release of spore components, and an increase in metabolism.
o An example would be anthrax.
Microbial Pathogenesis


Causes 18,000,000 deaths/year. Common in third-world countries.
Terms
o Symbiosis- living together
o Mutualism- both benefit
o Commensalisms- one benefits/other unharmed



o Parasitism
 Definitions
 Infectious disease is any change from state of health to one
in which all or part of the host body is not properly adjusted
or capable of carrying on normal functions due to presence
of parasitic agent.
 Pathogen is any parasitic agent which causes infectious
disease
 Pathogenicity is ability to cause such a disease
 Virulence refers to degree or intensity of pathogenecity
 Invasiveness is ability of organism to spread to adjacent
body sites
 Infectivity is ability to establish focal point of infection
 Toxigenicity is ability to produce toxins
Spread of Microbes
o Epithelial spread
o Lymphatic spread
o Hematogenous spread (sepsis)
 This produces secondary foci. It is no longer local.
 This can cause septic shock, hypotension, etc.
Host defenses
o General barriers
 Physical
 The skin is the first line of defense. It is thick, has a
decreased pH, and there is a fatty acid layer. There is
increased risk in moist and damaged skin.
 Urinary tract flushes out bacteria, etc. Women are generally
more affected than men due to the decreased length in
urethra.
 Respiratory tract contains reflexes such as coughing, as
well as the mucous system, etc.
 Intestinal tract also contains mucous, juices (pH),
antibodies, etc.
 Biological (Normal microbiota)
 Mutualism and commensalisms
o Either prevent harmful growth or use nutrients, etc.
that other bacteria wants.
o Even normal microbiota cause disease during
immunosuppression or if normal microbiota moves
to an area that it should not.
 Chemical (Antimicrobials)
Determinants of infectious disease
o To cause disease, a pathogen must be able to
 Contact the host by mechanical means or vectors.
 Adhere to, colonize, and invade the host


Adherence factors
o Adhesions, pili, etc.
 Virulence factors
o Genes producing toxins, anything that damages the
cell.
o Factors enhancing invasiveness
 Grow or complete lifecycle on or inside the host (meaning that the
host cannot die immediately)
 Certain requirement must be met
 At least initially evade the host defense mechanisms
 Many different mechanisms involved in host defense
o Production of toxins to overcome defenses and
protective coatings, capsule, or cling tightly.
 Have the mechanical, chemical, or molecule means to damage the
host.
 Production of toxins to damage host, other than defense
cells
 Production of boil
 Bacteria piling up on each other
 On CL, catheters, metal, etc.
 Attachment
 Expansion
 Maturation- produce a slime layer
 Resistance- Ab cannot penetrate deepest layers.
Bacteria cause disease by two major mechanisms once in contact.
o Intoxication
 Both exotoxins and endotoxins by themselves can cause
symptoms. The presence of the bacteria in the host is not required.
 Exotoxins
 These are polypeptides released by several gram + and
gram – bacteria. Exotoxins are among the most toxic
substances known. Exotoxins may be divided into three
categories on the basis of the site affected.
o Neurotoxins (nerve tissues)
o Enterotoxins (intestinal mucosa)
o Cytotoxins (general tissue)
 Examples of exotoxins are tetanus and botulinum, which
are both neurotoxins. Exotoxins are associated with specific
diseases but are unable to produce a fever in the host
directly. They are highly immunogenic.
 Endotoxins
 These are integral parts of the cell wall of gram – rods and
cocci. Endotoxins are the lipid portion of the
lipopolysaccharide outer membrane and produce
generalized effects of fever (i.e., are pyrogenic) and shock.

They are weakly immunogenic, and not as powerful as the
exotoxins.
 Adhesion of the bacteria can also cause problems.
o Infection
 This results from the pathogens growth, reproduction, and
invasiveness that often results in inflammation and ultimately
tissue alterations. Several enzymes secreted by invasive bacteria
play a role in pathogenesis, e.g., collagenase and hyaluronidase.
Inflammatory Response to Infectious Agents
o Suppurative Polymorphonuclear (PMN). This is acute, pus-forming
pyogenic bacteria, usually gram positive, i.e. strep.
o Mononuclear Inflammation- this is chronic infection, usually due to
viruses.
o Cytopathic- cytoproliferative inflammation
o Necrotizing inflammation- kills cells
o Chronic inflammation and scarring- chronic viral (hepatitis)
Classes

Staphylococci
o These are spherical bacteria found in grape-like clusters.
o Disease states and Symptoms
 These can be a part of the normal flora or agents of disease. They
are normally associated with the skin, skin glands, and mucous
membranes. It may persist on inanimate objects for a few hours.
 Staph aureus causes skin abscesses, boils, scalded skin syndrome,
wound infections, pneumonia, toxic shock syndrome, food
poisoning, and pericarditis. Ocular conditions include
conjunctivitis, blepharitis, corneal keratitis, and hordeolums.
 Staph epidermidis can cause endocariditis and infections of
patients with lowered resistance, along with ocular infections.
 Staph skin infections are the most common bacterial infections in
humans. This includes impetigo, cellulitis, mastitis, furuncles,
carbuncles (boils), etc.
 Folliculitis- This is an inflammation of the hair follicles. It
can appear as red bumps with pus.
 Felon- This is an infection of the finger pulp. It is swollen
with pus.
 Paronychia- This is bacteria in a hang nail. Red, tender,
swollen. Treatment includes incision and drainage. It will
not heal with just antibiotics, because the area is sealed off.
 Most common cause of osteomyelitis, endocarditis, and
pneumonia, especially in post-op patients or those following
respiratory infections.
 Osteomyelitis
o Bone scan done with a nuclear tag. Treatment
includes antibiotics or surgery to remove the bone.
 Endocarditis
o Seen with IV drug use or in hospitals. Rough/little
holes appear in the heart valve.
o An embolus can cause gangrene and other problems
in the hands and feet.
 Staphylococcal food poisoning
 This is the most common type of food poisoning and is
usually associated with mayonnaise or cream, usually unrefrigerated. It is caused by the ingestion of improperly
cooked food (ham, processed meats, chicken salad,
pastries, ice cream, etc) in which Staphylococcus aureus
has grown.
 Six different enterotoxins have been identified. The
bacteria are very resistant to heat, drying, and radiation.
 It is found in the nasal cavities and on the skin of humans
and other mammals. It is then spread via sneezing, which is
why sneeze screens and refrigeration on salad and food
bars are so important.
 Symptoms have a rapid onset, within 2-6 hours. This
includes short-lived abdominal pain, nausea, vomiting, and
diarrhea.
 Antibiotic therapy not helpful. Only time is. Treatment with
fluid and electrolyte replacement. Antidiarrheals will slow
the clearing process, so these are not recommended.
 Scalded skin syndrome
 The skin peels off due to toxins. It is very hard to treat, but
most use antibiotics.
 Toxic Shock Syndrome (TSS)
 Occurred in females using superabsorbent tampons
o Toxin associated with syndrome produced in men
and nonmenstruating women by S. aureus but at
different sites in the body.
o Transmission: This is part of the normal flora, but an over-abundance can
cause disease
 Spread by direct contact, so hand-washing is the most effective
means of prevention.
 It usually requires a portal of entry (abrasion, etc) to cause disease.
The exception is syndromes associated with toxin production.
o Pathogenic mechanism: These cause disease by producing exotoxins and
causing inflammation. Abscesses form, undergo central necrosis and
usually drain to the outside. Organisms occasionally disseminate via the
blood stream as well. Bacteremia from any localized lesion is common
and leads to endocarditis and metastatic abcesses in other organs.
 Toxins produced by Staph



Release exotoxins, vs. endotoxins released by GExamples
o Epidermolytic toxins A and B (exfoliatins)Dissolve peptidoglycans in epidermis (scalded skin
syndrome)
o Enterotoxins A-E- Exotoxins affecting gut
peristalsis (food poisoning)
 Leads to cramps, diarrhea, and vomiting.
o TSST-1- Toxic shock syndrome 1- A superantigen
which stimulates massive release of IL-1, IL-2, and
TNF (tissue necrosis factor, interleukins)
Exotoxins are not cured with antibiotics, because they are
already released
o Virulence Factors



Protein A- Binds to Fc segment of Ig, thus inactivates the
complement cascade
 Catalase- Inactivates H2O2
 Coagulase- Coat bacteria with fibrin, rendering them resistant to
opsonization and phagocytosis
 Firbrinolysins- Break down clots and allows spread to contagious
tissues
 Hyaluronidase- Hydrolyzes peptidoglycans (extracellular matrix)
and allows spread to contigous tissues
o Diagnosis: culture, staining, and symptoms
 In a gram stain, no information is present about the subspecies
present. It is Gram +. Grape-like cocci clusters are seen.
 Catalase test is used to differentiate staphylococci from other
gram-positive cocci. All staph produce catalase. This defines the
genus.
 Coagulase test is the basis for separating S. aureus from numerous
other, less pathogenic, strains of the same genus. This defines the
species. S. aureus produces coagulase.
 Cultures produce hemolytic colonies, yellow or white on blood
agar
 This is associated with PMNs (cause a PMN response)
o Immunity from infection: S. aureus is very resistant to penicillin. Normal
flora keeps it in check. Cleanliness, frequent hand washing, and aseptics.
o Drug-resistant strains now emerging (MRSA and VRSA)
 Methasiline resistant SA and vancalysin resistant SA
 See no clearing on the antibiotics plates around the sample.
Coagulase-negative Staphylococci
o This is part of the common skin flora and is a common contaminant of
blood cultures.
o This is rarely pathogenic, unless a foreign body (medical device) is present
in the patient (i.e., IV, pacemaker)
o Coagulase test is negative, non-hemolytic on blood agar.
o S. saprophyticus may cause UTI in young females.
Streptococcus, Diplococci
o These are spherical, nonmotile G+ bacteria that grow in long chains. Many
types are human pathogens. It is a part of the expected flora of skin and
mouth (epithelium), as well as the oropharyngeal flora in ~20% of adults.
o Typed via their surface (Lancefield) antigens. Group A is most important.
 Group A: Strep Pyogenes
 B-hemolytic, strep throat
 Group B: Strep agalactiae
 This is seen more in newborns and post-partum infections.
It is the leading cause of neonatal pneumonia, meningitis,
and sepsis. There is a 30% mortality rate.
 This is part of the expected vaginal flora in 30% of women.
The mother is usually asymptomatic. Less than 1% of the
colonized infants develop disease. The onset of the disease
is within four weeks of delivery. This disease is screened
for. Antibiotics use before delivery is not appropriate.
 Group C: Normal flora causing no infections.
 Group D: Enterococcus. Bowel related bacteria.
 This is a newer classification.
o Disease States and Symptoms
 S. pyogenes is the most common species causing disease in
humans (e.g., strep throat).
 S. pneumoniae causes pneumococcal pneumonia and many other
respiratory related infections.
 Strep is lancet-shaped and encapsulated.
 Disease State: This is the most common etiological agent of
bacterial pneumonia. It is responsible for more deaths than
any other infectious disease of the lower respiratory tract.
Other diseases include bacteremia, meningitis, and
infections of the upper respiratory tract such as otitis and
sinusitis. Symptoms include sudden chills, fever, cough,
and pleuritic pain, along with red or brown sputum. It is
also one of the most common causes of bacterial
conjunctivitis.
o African-Americans have a 3-5x high incidence of
bacteremia than whites, and the rates of invasice
disease are also exceptionally high among Native
Americans.
o Lobar pneumonia
 Only one lobe of the lung affected
 See the lung opacified with pus on a CXR or
in a gross lung.
 With high power photomicrograph, see
numerous PMNs.
o Spontaneous pneumococcal peritonitis
 Infection of abdominal wall.
o Pneumococcal sepsis
 Asplenic- more at risk
 Allows collection of bacteria.
o Pneumococcal meningitis
 With a CT scan, see pus and air.
 Pathogenic Mechanism: Pneumococci produce IgA
protease that may enhance the organism’s ability to
colonize the mucosa of the URT. They multiply in tissues
and cause inflammation. Factors that lower resistance
predispose persons to pneumococcal infections, e.g.,
depressed cough reflex, abnormalities of the respiratory
tract, chronic diseases, etc.







Transmission: Pneumococcal infections are not considered
to be communicable since a high percentage of healthy
individuals harbor virulent organisms in the oropharynx.
 Diagnosis: In the sputum, pneumococci can be seen as
predominant organisms in gram-stained smears. On blood
agar, pneumococci form small alpha-hemolytic colonies,
displaying a green zone of incomplete lysis of red blood
cells around the colonies.
 Immunity: A polysaccharide vaccine is fairly effective and
lasts at least 5 years.
Pharyngitis. This is an inflammation of the pharynx. Symptoms
include sore throat, exudates, fever, leukocytosis, and tender lymph
nodes. This is caused by group A S. pyogenes (strep throat), with
possible sequelae of scarlet fever (exotoxin), toxic strep syndrome
(“flesh-eating” bacteria) or rheumatic fever (cross-reactivity of Mprotein with cardiac myosin).
Otitis, sepsis, sinusitis, meningitis, pneumonia, etc.
Scarlet fever
 Red rash
 Finely raised (like sandpaper)
Toxic Strep Necrotizing Fasciitis
 Need to take off the skin (fasciotomy)
Rhematic fever
 Preventable with treatment
 Toxin related.
 Causes aortic stenosis
o Thickened, tight valves
o Heart murmurs
o Inflammation/infection of valves.
Skin infections
 Impetigo
o Bacterial infection on the face and skin.
o Group A strep
o “Honey-colored crust” Most lesions the same.
Around the face.
o Kebner phenomenon- you can spread the infections
yourself with a scratch.
 Erysipelas- facial cellulitis
o Caused by group A strep
o Common in those with DM
o Superficial.
 Cellulitis with lymphangitis
 Puerperal sepsis- postpartum infecting mom.
 Erythema nodosum
o Tender red nodules on the anterior shins.
o Independent of treatment


Post-streptococcal glomerulonephritis
 This is a disease of the kidney. It deals with IgA vs. protein
deposition from the blood to urine, causing swelling.
 This is rare, reversible, and can occur independent of
treatment.
 It also causes lid and orbital cellulites and in some cases uveitis
and conjunctivitis.
 Symptoms result from tissue damage via the action of toxins and
enzymes.
 Extracellular enzymes break down host molecules
 Streptokinase dissolves fibrin in clots by clearing
plasminogen. This is used to treat MI/CI.
 Hyaluronidase hydrolyzes the ground substance of
connective tissue.
 Erythrogenic toxin causes rash in scarlet fever.
 Streptolysin O causes beta hemolysis on a blood agar plate,
which is a clear zone around colonies secondary to
complete hemolysis of red blood cells. It is also antigenic.
 Streptolysin S is a hemolysin that is not antigenic.
 Cytolysins kill host leukocytes
 Capsules and M protein retard phagocytosis
o Transmission: This is part of the normal flora, but it can cause disease
when it gains access to tissue or blood. It is spread via respiratory droplets,
as well as direct and indirect contact.
o Diagnosis: culture, staining, and symptoms
 Gram stained smears from skin lesions or wounds reveal G+
spherical cocci found in chains or pairs.
 Catalase –
 May or may not exhibit hemolysis.
o Treatment: Normally sensitive to penicillin, but drug-resistance is
emerging.
o Immunity: Prevention of spread and antibody.
 Prevention (meningitis)
 Pneumovax
o This is a polysaccharide vaccine available for
adults, covering most of the bacteremic strains of
penumococcus (23 strains). Unfortunately, the
vaccine is administered to only about 30% of
susceptible patients
 Prevanar
o Children respond poorly to polysaccharide antigens,
so a heptavalent vaccine linked to diphtheria toxin
was developed. It was recently approved by the
FDA for use in children.
o Treatment: Penicillins or erythromycin
Corynebacterium diptheriae

o Disease State and Symptoms
 Diphtheria
 The most prominent sign is a thick, gray, adherent
membrane over the tonsils and throat. Nonspecific signs
include thick nasal discharge, fever, cough, sore throat, and
cervical adenopathy. Three prominent complications are
o Extension of the membrane into the larynx and
trachea, causing airway obstruction
o Myocarditis accompanied by arrythmias and
circulatory collapse
o Recurrent laryngeal nerve palsy
 The diptheria exotoxin causes the inflammatory response
and pseudomembrane
o The exotoxin can be absorbed into the circulatory
system and be distributed throughout the body. This
can lead to the destruction of cardiac, kidney, and
nervous tissues by inhibiting protein synthesis.
o Transmission: Humans are the only natural host of C. diptheriae. Both
toxigenic and non-toxigenic organisms reside in the upper respiratory tract
and are transmitted by airborne droplets. The organism can also infect the
skin at the site of a preexisting skin lesion. It is primarily a disease in the
tropics and in indigent populations with poor skin hygiene and overcrowded environments. It is very resistant to drying.
o Pathogenic Mechanism: Invasion and production of termerate phageencoded exotoxin inhibits protein synthesis by ADP-ribosylation of
elongation factor 2 (EF-2).
 Not all C. diptheriae cells produce this exotoxin and are therefore
nonpathogenic.
o Diagnosis: A throat swab should be cultured on Loffler’s medium, a
tellurite plate, and a blood agar plate. If C. diptheriae is recovered from
any of the cultures, either animal inoculation or a gel diffusion precipitin
test is performed to document toxin production. Smears of the throat swab
should be stained with gram’s stain to see tapered, pleomorphic Gram+
rods. Methylene blue reveals metachromatic granules.
o Immunity: The disease is easily prevented by immunization with
diphtheria toxoid (DPT vaccine). Otherwise, antitoxin should be given
immediately because the toxin’s effects are irreversible once inside the
cell.
o Treatment: Penicillins or erythromycin
Listeria monocytogenes
o Disease States and Symptoms
 L. monocytogenes causes meningitis and sepsis in newborns and
immunosuppressed adults. Infections during pregnancy can also
cause abortion or premature delivery during the peripartum period.
o Transmission: The organism is distributed worldwide in animals, plants,
and soil. From these reservoirs, it is transmitted to humans by direct


contact with animals or their feces, by unpasteurized milk, and by
contaminated vegetables. Newborns are infected as a result of
transplacental transmission or during delivery.
o Pathogenic Mechanism: The GI tract is the most likely source of
infections that arise endogenously. The pathogenesis of Listeria is
dependent upon the organism’s ability to parasitize mononuclear
phagocytic cells and to induce granuloma formation.
o Diagnosis: Rod-shaped Gram + organisms clump and resemble Chinese
characters. Bacteria are motile and appear to tumble. They produce gray
colonies on blood agar with zones of beta-hemolysis.
o Immunity: Limiting the exposure of immunosuppressed patients to
potential sources, such as infected animals, their products and
contaminated vegetables is recommended.
Bacillus
o Disease State and Symptoms
 B. anthracis causes anthrax
 This results in skin infections (painless, black, necrotic
ulcer with considerable edema). Bacteremia and death can
follow if left untreated.
 B. cereus causes food poisoning.
 This can produce two types of clinical syndromes
depending on where the toxin takes effect.
o Nausea and vomiting a short time after food is
ingested.
o Profuse diarrhea about 16-18 hours after food is
ingested.
o Transmission: B. anthracis spores are present in infected animal products
and infect humans by gaining access through mucous membranes, the
respiratory tract, or broken skin. B. cereus spores on grains germinate
upon the rewarming of food.
o Pathogenic Mechanism: B. anthracis produces anthrax toxin comprised of
a protective antigen, an edema factor, and a lethal factor. Capsules
interfere with phagocytosis. B. cereus produces two enterotoxins.
o Diagnosis: B. anthracis are Gram + rods with square ends and are
surrounded by a capsule. Both B. anthracis and B. cereus form spores.
o Immunity: The protective antigen component of B. anthracis anthrax toxin
is administered prophylactically as a vaccine to those at high risk for
exposure.
Neisseria meningitides (“Meningococcus”)
o This is considered one of the pyogenic cocci. They produce pus, but are
not Gram +. This is part of the oropharyngeal flora in 5-15% of the
population. Epidemics often occur in college dormitories or summer
camps.
o Disease State and Symptoms
 N. meningitis mainly causes meningitis. This is rare.


Although carriers are usually asymptomatic, cold-like symptoms
and rashes can be seen. The release of exotoxins decreases the
blood pressure, causes septic emboli, and gangrene.
 Can also cause sepsis, with resultant shock and profound
disturbances in coagulation.
o Transmission: N. meningitis organisms are transmitted by airborne
droplets to the nasopharynx, their initial colonization site.
o Pathogenic Mechanism: The organisms colonize the membranes of the
nasopharynx and become part of the transient flora of the upper
respiratory tract. From the nasopharynx, the organism can enter the
bloodstream and spread to specific sites, such as the meninges or joints, or
throughout the body. Meningococci have three important virulence factors
 A polysaccharide capsule that interferes with phagocytosis by
PMNs.
 Endotoxin causes fever, shock, and other pathophysiologic
changes, etc.
 IgA protease cleaves secretory IgA which interferes with the
bacteria’s ability to attach to membranes of the URT.
o Diagnosis: smear and culture of blood and spinal fluid samples show G –
cocci. The organism grows best on chocolate agar.
o Immunity: Resistance to this disease correlates with the presence of
antibody to the capsular polysaccharide. Most carriers develop protective
antibody titers within two weeks of colonization. Immunity is groupspecific, so it is possible to have protective antibodies to one group of
organisms yet be susceptible to infection by organisms of the other groups.
Complement, a coating to kill the bacteria, is an important feature of the
host defenses, because people with complement deficiencies, particularly
in the late-acting complement components (C5-C8), have an increased
incidence of meningococcal bacteremia.
 The vaccine is not widely used in the US except in military recruits
and during outbreaks. This is usually seen in closed environments.
Vaccinate susceptible patients during times of outbreaks, along
with prophylactic antibiotics (rifampin or 3rd generation
cephalosporins).
Neisseria Gonorrhea
o Nonmotile, aerobic , G – diplococci
o Disease states and Symptoms:
 Gonorrhea
 The patient may be asymptomatic.
 Gonococcal Infections
o Gonococcal urethritis- Gonorrhea in men is
characterized primarily by urethritis accompanied
by disuria and a purulent discharge.
o Gonococcal salpingitis- In women, infection is
located primarily in the endocervix (fallopian tube),

causing a purulent vaginal discharge and
intermenstrual bleeding.
o Fitz-Hugh-Curtis Syndrome
 Liver inflammation due to pelvic
inflammatory disease.
 Causes gonorrhea-related hepatitis.
 Hyperacute, mucopurulent conjunctivitis. If untreated, can lead to
severe corneal ulcer. Ophthalmia neonatorum occurs in infants
after passage through the birth canal of infected mothers. This
must be treated with silver nitrate soon after birth to prevent
blindness. Tetracycline and erythromycin are also used. It may
also cause corneal ulcers, conjunctivitis, keratitis, and blindness.
o Transmission: This is usually transmitted sexually. It is widespread due to
a lack of abnormal symptoms. Neonates can be affected and acquire the
ocular portion of the disease from the infected mother during birth. Points
of entry are the genitals, anorectal region, and pharynx.
o Pathogenic Mechanism: Pili mediate attachment to mucosal cell surfaces
and epithelial cells. Since these are often phagocytosed by host cells, the
host defenses are worthless. Once attached, they proliferate inside warm,
mucus secreting epithelia. Endotoxin and the other membrane proteins in
cell walls provide virulence. IgA protease functions as stated above. This
can penetrate the intact cornea.
o Diagnosis: This depends on Gram staining and culture of the discharge.
The finding of gram-negative diplococci within PMNs in a sample of
urethral discharge is sufficient for diagnosis. Cultures must also be used in
diagnosing suspected pharyngitis or anorectal infections. Specimens are
cultured on Thayer-Martin medium, which is a chocolate agar containing
antibiotics to suppress the normal flora. Neisseria grows poorly on blood
agar.
o Immunity: N. gonorrhea has constant programmed genetic variations
which makes it difficult to devise a vaccine to develop immunity.
o Treatment: Penicillin plus probenecid, ampicillin plus probenecid,
cephalosporin plus doxycycline, or spectinomycin
 A B-lactam inhibitor is required, because this bacteria produces Blactamase.
Salmonella
o This is a G – rod.
o Disease States and Symptoms
 This is one of the most common causes of bacterial enterocolitis
(e.g., S. typhimurium), enteric fevers (e.g., S. paratyphi) such as
paratyphoid and typhoid fever (S. typhi), and septicemis (e.g., S.
choleraesuis) which can lead to metastatic abscesses.
 After an incubation period of 6-48 hours, enterocolitis
(Salmonellosis) begins with nausea and vomiting, progressesing to
abdominal pain, cramps, fever, and diarrhea, which can vary from
mild to severe, with or without blood. Usually the disease lasts a
few days, is self-limited, and does not require medical care except
in the very young and old. 1.4 million cases/year.
 In typhoid fever, the onset of illness is slow, and is characterized
by the presence of fever and constipation rather than vomiting and
diarrhea. Once bacteremia has established, the patient will
experience a high fever, delirium, tender abdomen, and enlarged
spleen. “Red spots,” i.e., rose-colored papules on the abdomen, are
associated with typhoid fever, but occur only rarely. The disease
begins to resolve by the third week, but severe complications such
as intestinal hemorrhage or perforation can occur. About 3% of
typhoid fever patients become chronic carriers, mostly women.
 The symptoms of septicemia begin with fever but little or no
enterocolitis and then proceed to focal symptoms associated with
the affected organ, frequently the bone, lung, or meninges.
o Transmission: The epidemiology of salmonella infections is related to the
ingestion of food and water contaminated by human and animal wastes. S.
typhi, the cause of typhoid fever, is transmitted only by humans, but all
other species have both a significant human and animal reservoir. Human
sources are either persons who temporarily excrete the organism during or
shortly after an attack of enterocolitis or chornic carriers who excrete the
organism for years. The most frequent animal source is poultry and eggs,
but poorly cooked meat products also have been implicated along with
their products and contaminated water. Dogs and other pets, including
turtles, are other sources.
o Pathogenic Mechanisms
 Enterocolitis is characterized by a penetration of intestinal
epithelial and subepithelial tissue, resulting in inflammation and
diarrhea. Strains that do not invade do not cause disease. A PMN
response limits the infection to the gut and the adjacent mesenteric
lymph node. Gastric acid is an important defense.
 In typhoid and other enteric fevers, infection begins in the small
intestines but few gastrointestinal symptoms occur. Lymphoid
aggregates present in the lamina propia in the small intestine. The
organisms colonize phagocytic cells in Peyer’s patches which
spread the infection to the liver, gallbladder, and spleen. This leads
to bacteremia causing fever and other symptoms due to endotoxin.
Invasion of the gallbladder can result in the establishment of the
carrier state and the excretion of the organism in the feces for long
periods.
 Septicemia accounts for only about 5-10% of all Salmonella
infections and occurs in one of two settings: patients with chronic
disease, such as sickle cells anemia or cancer, or a child with
enterocolitis. Metastatic abscesses occur in organs as well as
previously damaged tissue, and frequently lead to osteomyelitis,
pneumonia, and meningitis.

o Diagnosis: In enterocolitis, the organism is most easily isolated from a
stool sample. As many as 1 billion bacteria/gram feces can be found.
However, in the enteric fevers, a blood culture is the procedure most likely
to reveal the organism during the first two weeks of illness. Salmonella do
not ferment lactose which appears as colorless colonies on McConkey’s or
EMB agar. On TSI agar, an alkaline slant and acid butt, H2S is produced,
which appears as a black area in butt.
o Immunity: Two vaccines are available that provide partial protection
against S. typhi.
 20% of all meat contains Salmonella. This is not heat resistant, so
cooking food would destroy it.
o Treatment: Fluid and electrolyte replacement
 84% are resistant to at least one antibiotic. This resistance is due to
increased antibiotic usage, therefore a ban on prophylactic use has
been called for.
Haemophilus influenza
o This is an encapsulated, small, nonmotile, G - coccobacillus.
o Disease State and Symptoms
 H. Influenza is the leading cause of meningitis in young children.
This type of meningitis cannot be distinguished on clinical grounds
from that caused by other bacterial pathogens. The rapid onset of
fever, headache, and stiff neck along with drowsiness is typical.
 Type B is encapsulated, and tissue invasion causes severe upper
respiratory tract infections, sinusitis, epiglottitis, otitis media,
meningitis, and sepsis, especially in children. Sinusitis and otitis
media cause pain in the affected area, opacification of the infected
sinus and redness with bulging of the tympanic membrane.
 It causes pneumonia in adults, particularly those with COPD.
 It may also cause acute, highly contagious, mucopurulent bacterial
conjunctivitis. This is seen as red eyes, itching, swelling of the lids
and a mucopurulent discharge.
o Transmission: This is part of the expected oropharyngeal flora in 30-50%
of adults. H. Influenza enters the body through the upper respiratory tract.
It can also enter an uncompromised corneal epithelium. It is commonly
found in day care centers.
o Pathogenic Mechanism: The organism produces an IgA protease that
facilitates attachment to the respiratory mucosa by degrading secretory
IgA. After becoming established in the upper respiratory tract, the
organism can enter the bloodstream and spread to the meninges.
Encapsulation and endotoxins are important for pathogenesis.
o Diagnosis: Growth of H. Influenza on blood agar requires heme (factor X)
and NAD (factor V) as growth factors for metabolism. Other species of
Haemophilus do not require both factors. Biochemical tests or quelling
reaction (capsular swelling tests) are more definitive. G – coccibacilli can
also be seen in exudates or spinal fluid through culture and serological
tests (ELISA).

o Immunity: Meningitis in close contacts of the patient can be prevented by
Rifampicin, which is secreted in the saliva to a greater extent than
ampicillin. Immunity can also occur through exposure. A diphtheria toxinconjugated vaccine (Hib) is available to prevent haemophilus-related
meningitis, but this is usually due to strep, which is treated with prevnar.
Pseudomonas
o It is an opportunistic G – motile aerobic rods.
o Disease States and Symptoms
 Pseudomonas aeruginosa causes infections virtually anywhere in
the body (e.g., sepsis, pneumonia, and urinary tract), primarily in
patients with lowered host defenses.
 From these sites, the organism can enter the blood, causing sepsis.
Patients with P. aeruginosa sepsis have a mortality rate of over
50%. A severe external otitis and other skin lesions occur in users
of swimming pools and hot tubs in which the chlorination is
inadequate. Bacteremia can lead to malaise, and if severe, to heart
valve damage.
 Ocularly, it causes lid itching, swelling, red eye, and mucopurulent
discharge. If untreated, severe necrosis of the cornea and
perforation can occur in 48 hours.
o Transmission: P. aeruginosa is found chiefly in soil and water although it
is a natural inhabitant of the colon. It is found on the skin in moist areas
and can colonize the upper respiratory tract of hospital patients. It can
occur after FB removal or ocular surgery. It is commonly found in burn
units. Its ability to grow in simple aqueous solutions has resulted in
contamination of respiratory therapy and anesthesia equipment,
intravenous fluids, and even distilled water.
o Pathogenic Mechanism
 P. aeruginosa is primarily an opportunistic pathogen that causes
infections in
 Hospitalized patients, especially those with extensive burns
so that the skin host defenses are destroyed. It causes 1020% of hospital-acquired infections.
 Chronic respiratory disease patients, e.g., cystic fibrosis,
with impaired clearance mechanisms
 Immunocompromised patients
 Those with neutrophil counts of less than 500/mL
 Those with indwelling catheters.
 Some species of Pseudomonas are resistant to disinfections. P.
aeruginosa produces two toxins.
 A secreted toxin, exotoxin A, inhibits eukaryotic protein
synthesis in a manner similar to siptheria toxin
 The structural exotoxin component in the outer cell wall.
o Diagnosis: case history, symptoms and laboratory determination
 P. aeruginosa grows as non-lactose-fermenting, colorless colonies
on MacConkey’s or EMB agar. It is oxidase-positive. Colonies


produce a metallic sheen on triple-sugar iron (TSI) agar. Growth
on agar produces a fruity odor.
o Immunity: Immediate treatment is necessary. If systemic, P. aeruginosa
can lead to death.
Moraxella
o Moraxella species are G – coccobacilliary rods resembling Neisseria.
Disease state and Symptoms
 This is the largest G – bacillus causing ocular disease (e.g., angular
blepharoconjunctivitis). Moraxella nonliquefaciens is one of the
two common causes of blepharitis. It masquerades as a viral
infection with follicles under the lids, resembling ocular
Chlamydia.
o Transmission: They are members of the normal flora of the upper
respiratory tract. It is associated with immunosuppressed individuals,
alcoholics, or rehabilitated patients, seen in institutions.
o Pathogenic Mechanism: This enters the cornea through compromised
epithelium. It is often associated with shared eye makeup.
o Immunity: Response is strong and quick to antibiotic therapy.
Spirochetes
o Three genera of spirochetes cause human infections. All are thin, long
organisms with corkscrew or spiral type shapes.
o Treponema
 This is a flexible spiral-shaped bacterium with periplasmic
bacteria.
 Disease State and Symptoms
 T. pallidum causes venereal and nonvenereal
treponematoses. There are three stages of Syphilis.
o Primary- A local, nontender ulcer (chancre) forms
at the site of infection 2-10 weeks post-inoculation.
This usually heals spontaneously.
o Secondary- A maculopapular rash (moist papules on
skin and mucous membranes) occurs 1-3 months
later and may heal spontaneously. Other
complications can include hepatitis, conjunctivitis,
fever, sore throat, and iritis.
o Tertiary- In three to four years after the initial
infection, 40% of untreated infections progress to
tertiary syphilis, which may show granulomas
(gummas), especially of skin and bones, CNS
involvement (e.g., paresis), or cardiovascular
lesions (e.g., aortitis, aneurysms). This is not
communicabale at this stage. The infected person
may become insane, blind, or deaf. Ocular
manifestations include interstitial keratitis,
chorioretinitis, Argyll-Robertson pupil, optic
neuritis, optic atrophy, and extraocular muscle
palsies.
 Transmission: The spirochete is sexually transmitted through
lesions of the skin or mucous membrane of an infected person to
unaffected persons by direct contact. It then migrates to regional
lymph nodes and is rapidly disseminated throughout the body. It is
not highly contagious. There is a 1 in 10 chance of acquiring the
disease through a single exposure to an infected partner. It can also
be transmitted from pregnant women to their fetuses. Rarely, blood
from transfusions collected during early syphilis is also infectious.
 Diagnosis: clinical case history, darkfield microscopy or
immunofluorescence.
 Nonspecific serological test (VDRL and RPR) detect the
presence of antibodies to organisms using nontreponemal
antigens.
 Specific (FTA ABS and MHA-TP) serological tests use
treponemal antigens.
 Immunity: There is no vaccine against syphilis. Humans respond to
T. pallidum with formation of antitreponemal antibody. Immunity
is not complete, therefore patients can be reinfected.
o Borrelia
 Disease State and Symptoms
 B. recurrentis, B. hermsii, and several borreliae cause
relapsing fever.
o Fevers, chills, headaches, and multiple organ
dysfunction in later stages of the disease. Often can
evade antibodies by switching surface antigens.
This is why they cause relapsing fever.
 B. burgdorferi causes Lyme disease.
o Early in the disease, fever, severe headache,
myalgia, stiff neck, and a “bull’s eye rash” occurs at
the site of the bite. If untreated, neuralgia and
cardiac abnormalities ensue weeks later, and
arthritis follows months to years later. Antigen
switching leads to relapsing fever.
 Transmission: Arthropods. The human body louse transmits B.
recurrentis while deer and mice ticks transmit other Borrelia
species via the bite.
 Diagnosis: B. recurrentis and B. hermsii are detected by seeing the
large spirochetes in stained smears of peripheral blood. B.
burgdorferi is usually diagnosed by detecting IgM antibodies by
immunofluorescent tests or ELISA.
 Immunity: Avoidance of arthropod vectors
 Treatment: Penicillin or tetracycline, amoxicillin, oral doxycycline.
o Leptospira



Causes leptospirosis, which is frequently found in rural water
supplies.
Actinomycetes
o Actinomyces Israeli: either G + or acid fast bacteria that form branching
filaments and resemble fungal hyphae.
 Disease State and Symptoms
 Actinomycosis- these are suppurative lesions, usually at the
face, neck, chest, or abdomen, but it may also affect eye.
The lesions are hard, swollen, and non-painful nodules.
 Transmission: A. Israeli is an anaerobe part of the normal flora of
the oral cavity. It produces infections following local trauma. It is
not communicable.
 Pathogenic Mechanism: Organisms invade tissues forming
filaments, and these filaments often surround sulfur granules.
 Diagnosis: G + branching rods in the presence of sulfur granules.
Growth when pus or tissue specimens are cultured under anaerobic
conditions. Immunofluorescene.
 Immunity: There is no vaccine.
o Nocardia asteroids
 Disease States: Nocardosis
 The disease begins as a pulmonary infection and may
progress to form abscesses in the sinus tracts.
 Pathogenic Mechanism: Nocardia uses filaments to invade tissues,
but these filaments can also fragment to aid in disseminating the
disease.
 Transmission: Nocardia species are aerobes found in the
environment, particularly in the soil. In immunocompromised
individuals, they can produce lung infection and disseminate.
 Diagnosis: Branching rods or filaments that are G + or acid-fast.
Organisms can be cultured aerobically.
 Immunity: No vaccine is available.
Mycobacteria (Koch’s Bacillus)
o M. bovis produces a GI infection from unpasteurized milk.
o M. tuberculosis
 This is an obligate aerobe.
 Disease State: Tuberculosis
 Fever, fatigue, night sweats, and weight loss are common.
Pulmonary tuberculosis causes cough accompanied by the
expectoration of bloody sputum.
 Transmission: Transmitted from person to person by respiratory
aerosol (coughing, sneezing) or the consumption of contaminated
animal products (milk).
 Pathogenic Mechanism: The initial site of infection is the lung.
Lesions depend on the presence of the organism and the host
response. Exudative lesions result from an acute inflammatory
response that occurs at the initial site of infections. Ganulomatous
lesions form when the bacteria grow and are surrounded by
lymphocytes, macrophages, and connective tissue to form a central
area of giant cells containing tubercle bacilli enclosed by
epitheloid cells. When these areas undergo caseated (cheese-like)
necrosis the produce small, hard nodiles called tubercules which
heal by fibrosis and calcification (are then called Ghon
complexes). For most people, the disease doesn’t progress further
since cell-mediated immunity keeps it contained. Reactivation can
occur in people at high risk for tuberculosis. In these cases, a
tubercle can erode into a bronchus, o rliquefy, so that the bacteria
can spread to others parts of the body such as lungs, GI tract, or to
other persons. Bacteria can also enter the bloodstream and spread
to the brain, kidneys, and bone.
 Diagnosis: Acid fast rods found in sputum or other infected
material. Chest xray, TB skin test.
 Immunity: After recovery from the primary infection, resistance to
the organism is acquired. This is mediated by cellular immunity. It
walls off bacteria in the lungs. Prior infection can be detected by a
positive tuberculin skin test, which is due to a delayed
hypersensitivity reaction. PPD (purified protein derivative) is used
as the antigen in the tuberculin skin test. 10% of patients undergo
reactivation years after overcoming primary infection or secondary
tuberculosis.
o M. leprae
 Disease State and Symptoms
 Leprosy or Hansen’s Disease.
o Leprosy is a severely disfiguring skin disease. The
incubation period averages several years, and the
onset of the disease is gradual.
o Hypopigmented macular skin lesions, thickened
superficial nerves, and significant anesthesia of the
skin lesions occur in tuberculoid leprosy.
o In lepromatous leprosy, multiple nodular lesions
occur, resulting in the typical lionlike faces.
 Transmission: This is generally transmitted to small children with
prolonged contact with patients who have lepromatous leprosy,
who are shedding M. leprae in large numbers in nasal secretions
and form skin lesions.
 Pathogenic Mechanism: The pathogen invades peripheral skin and
nerve cells and becomes an obligate intracellular parasite,
eventually killing the cell. The organism replicates intracellularly,
typically within skin histiocytes, endothelial cells, and the
Schwann cells of the nerves.
 Diagnosis: Acid-fast stain of skin lesions or nasal scrapings, PCR,
and the lepromin skin test, which is analogous to the TB skin test.


Immunity: Prevention of spread by isolation of all lepromatous
individuals. Cell-mediated immunity prevents 75% of the
individuals with initial lesions from progression to more serious
states of the disease.
o Diagnosis: Sulfur granules. These are acid-fast bacilli which gram stain
poorly secondary to high lipid content of cell walls. Slightly curved or
straight aerobic rods, sometimes branch to form filaments.
Chlamydia
o These are obligate intracellular parasites that lack a mechanism for the
production of energy, and therefore grow only inside host cells. Their cell
walls resemble those of G – bacteria.
o Disease State and Symptoms
 C. psittaci causes psittacosis.
 C. psittaci primarily infects the lungs. The infection may be
asymptomatic or may produce high fever and pneumonia.
Human psittacosis is usually not communicable.
 C. trachomatis causes ocular, respiratory, and genital tract
infections.
 This exists in more than fifteen immunotypes. Types A, B,
C cause trachoma, while types D-K cause genital tract
infections, which are occasionally transmitted to the eyes or
the respiratory tract. These types are the cause of the most
common sexually transmitted disease. In men, it is a
common cause of non-gonococcal urethritis. In women,
cervicitis develops. In infants born to infected mothers,
mucopurulent eye infection often develops 7-12 days after
delivery.
 Trachoma: These are inclusion bodies within cells, leading
to a conjunctivitis that is the number one cause of
blindness.
o After proliferating in the mucosa of the upper lid,
the pathogen extends to the cornea resulting in
corneal scarring and eye deformation.
o It usually is found in crowded populations living in
unsanitary conditions.
o Stages of trachoma
 Stage I: Incipient, may be asymptomatic.
 Stage II: Presence of follicles, papillary
hypertrophy and possibly pannus.
 Stage II: Trichiasis, entropion, pannus,
conjunctival scarring.
 Stage IV: Post-inflammatory or healed
stage. May be asymptomatic. Scar tissue is
seen.
 Inclusion conjunctivitis

o This is a less severe eye disease that is contracted
by swimming in unchlorinated water that has been
contaminated. Infection does not result in blindness.
Newborns can get it from mother.
 Lymphogranuloma venereum
o This begins with the formation of painless genital
lesions which release pathogens into the
bloodstream. The pathogen invades the meninges,
eyes, joints, and persists in the lymphatics causing
stasis and elephantitis. Ocular findings are rare.
 C. pneumoniae causes atypical pneumonia.
o Transmission:
 C. psittaci is transmitted to humans primarily by inhaling
organisms in dried bird feces.
 C. trachomatis infects only humans and is usually transmitted by
close personal contact, e.g., sexually, or by passage though the
birth canal. In the case of eye disease, C. trachomatis is transmitted
by finger-to-eye or fomite-to-eye contact.
 C. pneumoniae is transmitted from person to person by aerosol.
o Diagnosis: Cytoplasmic inclusion bodies are visible within cells stained by
Giemsa stain or by immunofluorescence. C. pneumonia and C. psittaci are
diagnosed using serological tests.
o Immunity: Infections by C. trachomatis lead to formation of antibodies
and cell-mediated reactions, but not to resistance to reinfection nor
elimination of organisms. Erythromycin and tetracycline are used to
suppress signs and symptoms, but usually do not eliminate the organism.
Erythromycin is given to newborn infants to prevent inclusion
conjunctivitis and pneumonitis.
Rickettsia
o All but one are obligate intracellular parasites. The majority of rickettsias
appear as coccobacillus. They have rigid cell walls and are generally
nonmotile.
o Disease State and Symptoms
 Rocky Mountain spotted fever is caused by R. rickettsii
 This is characterized by the acute onset of fever, severe
headache, myalgias, prostration, and a typical rash that
appears first on the hands and feet and then on the trunk
within 2-6 days. Other severe CNS changes such as
delirium and coma can occur if disease left untreated.
 Q fever is caused by Coxiella burnetii.
 Q fever occurs in the lungs and begins suddenly with fever,
severe headache, and influenza-like symptoms. If left
untreated, pneumonia may ensue. Hepatitis occuassionally
develops. No rash occurs.
 Rickettsias are also responsible for Brill-Zinsser, endemic typhus,
and scrub typhus.


o Transmission: This is transmitted to humans by arthropods bites (ticks,
lice, fleas, and mites. Q fever which is spread by inhalation of an infected
aerosol.
o Pathogenic Mechanism: The typical lesion caused by Rickettsia is
vasculitis, particularly in the endothelial lining of the vessel wall where
the organism is found. Damage to the vessels of the skin results in
increased capillary permeability ultimately causing the characteristic rash,
edema, and hemorrhaging. There is evidence that endotoxins are involved,
but it is unconfirmed. In humans, Rickettsias produce a toxin which can be
neutralized by homologous group-specific antiserum. They also produce a
hemolysin which lyses the red blood cells of rabbits and sheep.
o Diagnosis: Laboratory diagnosis is based on serological analysis via the
complement fixation test and the Weil-Felix test.
o Immunity: Vaccinations are available those at high risk of developing Q
fever.
Streptomycetes
o This is an aerobic G + bacteria that appear “fungus like.” They form
branching filaments, or hyphae, and asexual spores. Most are nonmotile.
o The genera streptomycetes plays a major role in ecology by aerobically
degrading resistant organic material. They also synthesize many medically
useful antibiotics, including erythromycin, tetracycline, and
chloramphenicol. Most streptomycetes are nonpathogenic.
Mycoplasma
o This is the smallest free-living organisms capable of reproduction. These
are prokaryotes that are pleomorphic in shape since they lack cell walls
since peptidoglycan precursors cannot be synthesized. Therefore, they are
penicillin-resistant, but susceptible to lysis by osmotic shock and detergent
treatment. Most are nonmotile, require sterols for growth, and are
facultative anaerobes.
o Disease State and Symptoms
 M. pneumoniae causes “atypical” pneumonia. A causative
bacterium cannot be isolated on routine media in the diagnostic
laboratory.
 The onset of M. pneumoniae is gradual, usually beginning with a
nonproductive cough, sore throat, or earache. Small amounts of
whitish, nonbloody sputum are produced. Constitutional symptoms
of fever, headache, malaise, and myslagias are common. The
patient can remain ambulatory and there is very low mortality.
o Transmission: Respiratory droplets. This is generally pathogenic to
animals and occasionally to humans. M. pneumoniae, which is remarkably
widespread, causes damage to epithelial cells in the airways. It can be
cultured from animals, plants, and soil.
o Pathogenic Mechanism: In the lungs, the organism is rod-shaped with a
tapered tip that contains specific proteins which serve as the point of
attachment to the respiratory epithelium. The respiratory mucosa is not
invaded, but ciliary motion is inhibited and necrosis of the epithelium




occurs. The mechanism by which pneumoniae causes inflammation is
uncertain.
o Diagnosis: culture, serological testing, and cold hemagglutinin.
o Immunity: The disease resolves spontaneously.
Legionella pneumophila
o Fastidious G- bacteria. Cut glass colony with iridescence.
o Disease State and Symptoms: Pneumonia-like.
 Legionnaire’s disease or legionellosis
 Symptoms include high fever, nonproductive cough,
headache, neurological manifestations, and severe
bronchopneumonia.
o Transmission
o Pathogenic Mechanism: Overcomes host defenses by taking up residence
within the alveolar macrophages  coiled phagocytosis does not fuse with
lysozyme, so it is not destroyed. Produces cytotoxic exoprotease
o Diagnosis
o Immunity: Prevent by preventing and treating contaminated water
o Treatment: Erythromycin or rifampin
Yersinia pestis
o G–
o Disease State: Plague
o Pathogenic Mechanism: Destruction of macrophages.
o Transmission: Infected fleas, direct contact with infected animals or their
products, inhalation of contaminated airborne droplets
o Immunity: Prevention and control by isolating infected populations.
Clostridium tetani
o This is an anaerobic G+ spore former
o Disease State: Tetanus
o Transmission
 Bacterium commonly found in hospital environments, soil, and
dust, feces of many farm animals and humans
 Transmission associated with skin wounds
o Pathogenic Mechiansm: Endospores enter, germinate, die, and lyse,
releasing the neurotoxin tetanospasmin (heat labile). These are stable and
resistance to the environment
Vibrio cholerae
o This is a slightly curved G – bacteria. It is normally aquatic, but dumps the
flagella when it enters the host.
o Disease State: Cholera
o Transmission: Ingestion of food contaminated by fecal material from
patients and carriers
o Pathogenic Mechanism: Secrete choleragen, an enterotoxin that stimulates
hypersecretion of water and chloride ions and inhibition of absorption of
sodium ions, causing abdominal cramps, vomiting, fever, and diarrhea.
o Treatment includes rehydration therapy, as well as tetracycline/
trimethoprim/ sulfa combination.




Califorms
o This is the general term for coli-like bacteria indicative of fecal
contamination. It is seen in beaches. Counts maxed out measurements at
30,000/ml in Rincon Pt. (Santa Barbara). Anything over 10,000 is labeled
as contamination, meaning that the beach is closed.
Escherichia Coli 0157:H7
o Usually E. Coli is part of the normal flora of the body, but this strain is
not.
o This is seen in beef from NE-based companies, Japenese radishes, and
WY tap water. Incidents continue despite an increase in stringent food
safety standards.
o The diet of cattle may play a role
 The digestive tract of the cattle has virulent strains, very resistant
to decreased pH.
 The Diet since WWII has been starch (vs. hay). Hay has <1% the
amount of E. Coli in the grain feed. Starch grows the cows faster
and is less expensive. Yet, this is better for bacteria to grow. It has
been found that switching to hay five days prior to slaughter
eliminated the acid-resistant E. Coli. Transporting cattle also
decreases the fecal discharge. Once manure is exposed to oxygen,
it is acid-resistant again
Campylbacter spp.
o This leads to about 4 million infection/year in the US.
o About 88% of poultry test positive for this, but it is killed with proper
cooking.
o Symptoms include mild to severe diarrhea, fever, nausea, vomiting, and
abdominal pain. They are usually self-limiting, but can become severe
leading to meningitis and Guillan-Barre Syndrome.
o There has been a strain identified that is resistant to all known antibiotics.
Helicobacter Pylori
o This is a Gram -, microaerophile, spirical bacillus. It is acid-resistant.
o It could be a part of the normal flora of the body. At least 30-50% of the
world population is contaminated with H. pylori. 70-90% in third worlds
is infected as kids. In developed countries, <10% of kids and <50% of
those 60 years old have it.
o Disease State: Responsible for chronic gastritis, peptic ulcers, and gastric
cancer. This is the first example of bacteria linked to cancer. There is also
a possible relationship with heart disease. Most are asymptomatic. <20%
positive for H. pylori have ulcers.
o If we have it, probably not virulent
o Transmission: This is found in food and water, and the transmitted from
person to person (also found in food and water), but the exact mechanism
is still unknown.
o Pathogenic Mechanism: The bacteria colonize in mucus-secreting cells of
the stomach with multiple polar flagella to propel quickly through the
mucus, colonizing each layer. They then produce ureases that leads to
localized neutralization of the stomach acids
 There is a high degree of genetic variability among different
strains, which is why they do not all cause cancer. Some strains
have a sequence (“pathogenicity island”) that increases the
virulence
o Treatment: Bismuth subsalicylate (Peptobismol) and various antibiotics
Laboratory Isolation, Culture, and Identification of Bacteria


Isolation of a pure culture
o Streak plate method: streak specimen over plate to isolate.
o Spread plate: dilution of a bacterial suspension is poured onto a plate.
o Pour plate: dilution of bacterial suspension is mixed into agar.
o Enrichment culture: growth-selective medium. Ex. Blood, chocolate, and
nutrients.
Culturing/Media: many different materials and methods non-synthetic, synthetic,
all-purpose, enriched, selective, differential, transport.
o Generally, organisms have specific or nonspecific nutritional and
environmental requirements that must be taken into consideration.
 To culture anaerobes specific techniques would be necessary.
 Important factors include nutrients (carbon trace nutrients),
fluidity, pH (6.5-7.5), oxygen content, and temperature (35-40º
centigrade).
o Measurement of growth: direct-microscopic count, turbidity, consumption,
waste production.
o Look for differential growth on various media
 Bacterial morphology
 Cocci (round), bacilli (rods), spiral (spirella, spirochete)
 Single, pair, or chains
 Colonial morphology
 Surface quality: smooth or rough
 Surface shape: raised, flat, indented
 Colony edge: regular, irregular, lobulated
 Consistency: thick, thin, mucoid
o Culture Origins
 Blood Cultures
 At least three 10-ml blood samples in a 24-hour period are
obtained because the number of organisms can be small
and their presence intermittent. The site for venipuncture
must be cleansed with 2% iodine to prevent contamination
by members of the flora of the skin, usually S. epidermidis.
The blood obtained is added to 100ml of a rich growth
medium such as brain-heart infusion broth. Blood cultures
are checked for turbidity or for CO2 production daily for 7
days or longer. If growth occurs, Gram stain, subculture,




and antibiotic sensitivity tests are performed. If no growth
is observed after 1-2 days, blind culturing onto other media
may reveal organisms. Culture should be held for 14 days
when endocarditis, fungemia, or infections by slowgrowing bacteria is suspected.
o Organisms most often isolated
 G + cocci: S. aureus and Strep pneumoniae
 G – rods: E. coli, Klebsiella pneumoniae and
P. aeruginosa.
 Suspect infections: sepsis, endocarditis, osteomyelitis,
meninges, or pneumonia.
Throat Cultures
 The swab should touch not only the posterior pharynx but
tonsils or tonsilar fossae as well. The material on the swab
is inoculated onto a blood agar plate and streaked to obtain
single colonies. If colonies or beta-hemolytic streptococci
are found after 24 hours of incubation at 35º C, a bacitracin
disk is used to determine whether the organism is likely to
be a group A beta hemolytic streptococcus. Bacitracin
inhibits growth of group A streptococcus.
o Suspect infections: pharyngitis, diphtheria,
gonococcal pharyngitis, thrush
Sputum Cultures
 A preliminary assessment of the cause of pneumonia can be
made by Gram stain. Serologic or biochemical tests provide
additional means to identify organism.
o Suspected infections: If TB, an acid-fast stain and
culture of the sputum on special media should be
done immediately. If aspiration pneumonia and lung
abscesses, anaerobic cultures are important.
Spinal Fluid Culture
 The Gram-stained smear of the sediment of the centrifuged
sample guides the immediate empirical treatment. If
organisms resembling N. meningitis, H. influenzae, or S.
pneumoniae are seen, the quelling test or
immunofluorescence with specific antisera can identify the
organism rapidly. Cultures are done on blood and on
chocolate agar and incubated at 35º C in a 5% CO2
atmosphere. Acid-fast sains of the spinal fluid should be
performed.
Stool Cultures
 A direct microscopic examination of the stool can be
informative from two points of view. A methylene blue
stain to identify the presence of leukocytes thus indicating
that an invasive organism rather than a toxigenic one is

involved, and a Gram stain to identify bacterial shape and
type.
o MacConkey or eosin-methylene blue (EMB) agar is
selective because they allow G – rods to grow but
inhibit many G + organisms. Differential properties
such as fermentation of lactose and selective growth
on antibiotic-containing media are also useful.
o Performed primarily for enterocolitis (frequently
caused by Shigella, Salmonella, and
Campylobacter).
 Urine Culture
 Urine in the bladder of a healthy person is sterile, but it
acquires organisms of the normal flora as it passes through
the distal portion of the urethra, therefore, a midstream
specimen is used for culture. Culture must be done 1 hours
after collection or refrigerated at 4º C for no more than 18
hours. A bacterial count of at least 100,000/ml must be
found to conclude that significant bacteriuria is present.
o Performed primarily when pyelonephritis or cystitis
is suspected.
 Genital Tract Culture
 Human cells or yolk sacs of embryonic eggs are necessary
for culturing Chlamydia trachomatis. Finding
intracytoplasmic inclusions when using Giemsa stain or
immunofluorescence is diagnostic.
 G – diplococci found intracellularly within neutrophils on a
smear of a urethral discharge from a man have over 90%
probability of being N. gonorrhea.
 Diagnosis of T. pallidum, the agent of syphilis is made by
microscopy (darkfield- motile spirochetes) and serology. T.
pallidum cannot be cultured.
 Wound and Abscess Culture
 Because anaerobes are frequently involved in these types of
infections, it is important to place the specimen in
anaerobic collection tubes and immediately transport to the
laboratory. It is important to culture the specimen onto
several different media under different atmospheric
conditions as multiple organisms often infect the wound.
Identification of microorganisms
o Staining
 Types
 Simple stain
 Differential stain: Gram stain, acid-fast stain
 Negative stain
 Specific stains: Flagella, spore, granule specific


Biochemical properties: Fermentation, pH, gas production,
catalase production, indole production, starch and gelatin
hydrolysis
 Preparation of slides for cytological examination
 When it comes to microbiology and the eye, conjunctival
and corneal ulcer scrapings using a sterile platinum spatula
usually yield more material and are easier to interpret than
swab specimens. Exudative and purulent material can also
be used for smears.
 Useful stains include DFA stains to identify C. trachomatis
and some viruses. Special stains are used to identify fungi,
certain bacteria (M. tuberculosis) and acanthamoeba.
 The two most useful stains regarding the eye and pathology
include a Gram stain to identify bacterial shape and gram
stain classification as well as cytological stains (Giemsa
and Diff Quick) to identify inflammatory cells present.
Immunologic Method
o Identification of an organism by use of antiserum
 Capsular Swelling (Quellung) reaction: several bacteria can be
identified directly by microscopic observation that the capsule
swells in the presence of homologous antiserum.
 Slide agglutination test: antisera can be used to identify Salmonella
and Shigella by causing clumping of the unknown organism.
 Latex agglutination test: Latex beads coated with specific antibody
are agglutinated in the presence of the homologous bacteria or
antigen.
 Counter-Immunoelectrophoresis test: in this test, the unknown
bacterial antigen and a known specific antibody move toward each
other in an electric field. If they are homologous, a precipitate
forms within the agat matrix. Because the antibody is positively
charged at the pH of the test, only negatively charged antigens can
be assayed.
 Enzyme-linked immunosorbent assay (ELISA): to detect the
presence of Chlamydia, HSV 1 and 2, and adenoviruses by use of
monoclonal or polyclonal antibody (i.e., antibodies that bind with
multiple antigens).
 Fluorescent antibody tests: antibody-antigen complexes are
identified by fluorescent tags.
o Serological tests for syphilis (since T. pallidum cannot be cultured)
 The nontreponemal tests use a cardiolipin-lecithin-cholesterol
mixture as the antigen, not an antigen of the organism. Cardiolipin
is a lipid extracted from normal beef heart. Clumping of the
cardiolipin occurs in the presence of antibody of T. pallidum. The
VDRL and RPR tests are inexpensive and commonly performed as
a screening procedure.

The most widely used treponemal test is the FTA-ABS test. The
patient’s serum sample, which has been absorbed with treponemes
other than T. pallidum to remove nonspecific antibodies, is reacted
with nonviable T. pallidum on a slide. Fluorescein labeled
antibody against human IgI is then used to determine whether IgG
antibody against T. pallidum is bound to the organism.
Treating Bacteria
Antiseptics and Disinfectants
 Definitions
o An antiseptic is an agent applied to living tissues to destroy or inhibit
growth of microorganisms, while a disinfectants is an agent or process
applied to inanimate materials to destroy pathogenic microorganisms
o Sterilization is the destruction of all life forms. Germicides are agents that
kill pathogenic microorganisms. Fungicides kill fungi. Sporicides kill
spores. Virucides kill viruses.
o A sanitizer is an agent that reduces pathogenic microorganism
contamination to a safe level.
o Disinfection is the removal of harmful organisms. There are some living
organisms, but they are not harmful. Disinfectants are chemicals that kill
or remove organisms which cause disease. Disinfectants vary in their
tissue-damaging properties: Disinfectants that end in the suffix “cide” are
usually lethal to the organism, whereas those ending in “static” prevent or
curb microbial growth. Disinfectants containing corrosive phenol
compounds are to be used only on inanimate objects. Less toxic materials,
such as ethanol and iodine can be used on skin surfaces (i.e., antiseptic
chemicals mild enough to use on living tissue).
 Physical agents
o Pasteurization: heating at 62º C for 30 min or 72 º C for 15 seconds.
o Boiling: 100º C, does not kill spores and some viruses.
o Autoclaving (moist heat): use of high temperature and high pressure to kill
microorganisms, steam under pressure at 121º C under a pressure of 15
lb/in2 for 15 min, kills spores and viruses.
o Dry heat: heat denatures protein, 121º C for 16 hours
o Moist heat kills bacteria, viruses, and fungi by causing nucleic acid
breakdown and protein denaturation. Bacterial and endospores require
boiling temperatures (achieved with autoclave).
o Radiation: UV light (240-280nm) causes DNA mutagenesis and
alterations/mutations that block replication. This is only useful for killing
pathogens on exposed surfaces since radiation does not penetrate
substances.
o Filtration- used to remove microbes from heat sensitive solutions on the
basis of size. Two types of filters are used: depth filters and membrane
filters. They work either by suction or by positive pressure and remove
microbes by screening them out like a sieve.

o Ultrasonic and sonic waves: denature protein (frequency > 15,000 cps)
o Freezing (-20º C)
o Physical agents act either by imparting energy in the form of heat or
radiation or by removing organism through filtration.
Chemical agents: degree of effectiveness depends on chemical and
microorganism.
o Acids and alkali
o Salts
o Heavy metals inactivate or precipitate proteins.
o Halogens
 Iodine
 Bactericidal, tuberculocidal, fungicidal, and virucidal. Also
an antiseptic and disinfectant
 Mechanisms (better than ethanols)
o Precipitation of proteins
o Oxidation of enzymes
 Preparations
o Iodine solution- 2% in KI solution
o Iodine tincture- 2% in hydroalcoholic solution
(iodine in water and EtOH)
o Iodophors
 This is Iodine complexed with a surfactant,
and the Iodine is released slowly after
application
 Povidone-iodine (Betadine)- most effective
 Chlorine
 Bactericidal, sporicidal, tuberculocidal, virucidal
(fungicidal at higher concentrations). Kills HIV (1:100
preparations/bleach). A disinfectant.
 Cl2 + H2O  HClO3 (Hypochlorous acid)
 Probable mechanism- Oxidation of proteins or other
components
o Halazone. For water disinfection
o Alcohols
 Bactericidal, tuberculocidal, fungicidal, and virucidal. It is a
disinfectant that has mild antiseptic properties.
 Mechanism- Denature bacterial proteins and possibly dissolve
membrane lipids.
 Preparations
 Ethanol. Most effective concentration is 60-70%
 Isopropanol. Most effective concentration is 100%
 Best to soak for 30 min.
o Oxidants: H2O2
 Antiseptic and disinfectant
 3% solution is bactericidal and virucidal
o Alkylating agents: formaldehyde

o
o
o
o
Aldehydes
 Mechanism- Alkylation of proteins
 Formaldehyde
o Formalin is an aqueous solution
o Low concentrations are bacteriostatic
o High concentrations (20%) are bactericidal,
sporicidal, tuberculocidal, and fungicidal
o Adverse effect- Irritation of mucous membranes
 Glutaraldehyde
o Bactericidal, sporicidal, fungicidal, virucidal.
Disinfectant
Synthetic detergents: quaternary ammonium compounds
 Agents
 Benzalkonium chloride (BAK)
 Cetylpyridinium chloride
 Mechanism- Denaturation of bacterial cell membrane and proteins
of cytoplasm
 Bacteriostatic in low concentrations and bacteriocidal (fungicidal)
in high concentrations. Both are antiseptics and disinfectant.
Cationic.
 Activity diminished by anionic detergents, soaps, tissues (blood
and cotton), as well as dilution in hard water (ions attach and
decrease activity).
Phenols: denature proteins and involves cell lysis (e.g., hexachlorophene
acts by injuring the plasma membrane of microorganisms).
 Derivatives of Phenol
 Hexylresorcinol
o Antiseptic
o Adverse effect- Burning of skin
 Hexachlorophene (pHisoHex)
o Antiseptic
o Used in soaps/ dandruff shampoo
o Film on skin is bacteriostatic
o Adverse effect- Spongiform degeneration of the
brain
Mercurials
 Thimerosal
 Weakly bacteriostatic (placebo?)
 Can cause severe renal damage
Chlorhexidine
 Mechanisms
 Disrupts bacterial cell membrane, inhibiting membranebound ATPase. This denatures bacterial cytoplasmic
proteins.
 Antiseptic and disinfectant
 Film on skin is bacteriostatic
 Used in preventing dental carries (cavities)
o Sterilant Gases
 Formaldehyde
 Formalin- bubbled into H2O
 Paraformaldehyde
 Ethylene oxide
 Penetrates porous materials
 Flammable
 Used in a concentration of 10%
 Mechanism- Alkylation of proteins and nucleic acids
 Can be used at ambient temperature and pressure, but
increasing temperature. Pressure, or concentration
decreases sterilizing time
 Plastics must be aerated after sterilization
 Beta-propiolactone- same as ethylene oxide
 Peracetic Acid- forms acetic acid and H2O2
 Ozone- used to purify water
o Silver Nitrate
 Used in low concentrations to prevent gonococcal infection in
newborns
 Turns skin brown
Anitbiotics/Antibacterials
General Principles
 An antibiotic is any chemical substance produced by a microorganism that is
harmful to other organisms. Worldwide spending for new antiinfectives was about
3 billion in 1998. This is up 60% from 1993. Most spent for HIV and hepatitis
(antivirals). It costs about $300 million to bring a new drug to market. Drugs are
only a few cents/pill to make, but the cost is in research and development. Only
1/10 of the drugs are safe and effective enough to make it to market.
 Selective affinity/toxicity
o Ehrlich discovered “magic bullets” that led to major discoveries in
antibacterial chemotherapy.
o His discovery of selectivity means that these drugs are toxic to the agent,
not to the host. Its basis is the evolutionary distance between bacteria and
humans It allows us to kill them and not vice versa. Differences manifest
in different macromolecules. The difficulty with some drugs in that some
differences are much less pronounced than others. This is the problem
with the endosymbiotic origin of mitochondria.
 Types
o Bactericidal agents kill bacteria, therefore are more effective during
periods of rapid growth. These effects are permanent.
o Bacteriostatic agents suppress growth and reproduction of bacteria so that
the immune system can fight the rest. These agents do not kill the bacteria



and are therefore generally less effective than bactericidal agents. The
effects can be reversible.
o Some drugs are one or the other, some are both
o Synthetic antimicrobials are any chemical substance harmful to
microorganisms that are not produced by a microorganism.
Effect of handwashing
o Without washing, mold, Gram – bacteria, and staph are all seen on the
hands.
o With washing, mostly staph is seen, because the skin loosens, releasing it.
This is not pathological unless it enters the skin.
Sensitivity
o Minimum inhibitory concentration (MIC)
 An organism isolated from a patient is inoculated into a series of
tubes or cups containing two-fold dilutions of the drug. After
incubated at 35º C for 18 hours, the lowest concentration that
prevents visible growth of the organism in otherwise adequate
conditions is the MIC.
 Disk diffusion method: disks impregnated with various antibiotics
are placed on the surface of an agar plate that has been inoculated
with the organism isolated from the patient. After incubated at 35º
C for 18 hours, during which time the antibiotic diffused outward
from the disk, the diameter of the zone of inhibition is measured.
The size of the zone of inhibition is compared to standards to
determine the sensitivity of the organism to the drug.
o Minimum bactericidal concentration (MBC)
 This is determined by taking a small sample from the tubes used
for the MIC assay and spreading it over the surface of a drug-free
blood agar plate. Any organisms that were inhibited but not killed
now have a chance to grow because the drug has been diluted
significantly. After incubated at 35º C for 48 hours, the lowest
concentration that has reduced the number of colonies by 99.9%, at
least 1000 fold, compared to the control with no drug is the MBC.
o Therapeutic index
 This is the ratio of the dose toxic to the host to the effective
therapeutic dose (TD50/ED50)
Susceptibility
o This is how an antibiotic that works. It is determined by testing multiple
antibiotics on a specific strain.
o Kirby-Bauer apparatus/technique


When bacteria are set at a specific density, time, evenly spread,
and a control is present, a clearing around the antibiotic disk means
that the antibiotic is working. This zone of inhibition must be
larger than a standard to be declared as susceptible.
o Other considerations- In vitro conditions (susceptibility). If it does not
work in the lab, do not give it to the patient.
o May be used for
 Determining necessary drug concentrations required to fight an
infection.
 Evaluation of resistant strains
 Selecting the most effective antibiotics
 Differential qualities: hemolysis, coagulase, catalase, oxidase,
fermentation, etc.
o Serology: Reaction with a specific antibody.
The antibacterial spectrum is the range of organisms against which an agent is
effective.
o A broad, wide, or expanded spectrum are effective against most agents,
both G + and –. These are prescribed more before the cause of the disease
is known.

o A narrow spectrum implies that it is effective only against a few agents. It
is more selective and effective. These are prescribed after the cause of the
disease is known.
Antibiotic Resistance
o Resistance is the ability of a microorganism to survive exposure to an
antimicrobial drug.
o This is generally due to either the decreased entry of the drug into the
organism, increased excretion of the drug from the organism, or the
metabolism of the drug outside of the organism. All mechanisms result
from chromosomal mutations in the organism or from entry of
extrachromosomal plasmids.
o Evolution of resistant strains
 Reasons for these trends
 Plasmids and transposons
 Linkage to virulence determinants (capsule, etc)
o Extremely dangerous
 Bacteria vs. pharmacological research
 Widespread use of antibiotics and antibacterials
o The amount of antibiotics given annually to
livestock in the US was 18 million in 1985 and 25
million in 1990. 7% of all antibiotics is given to
livestock is to treat disease
o With a ban of antibiotics came a decreased
resistance. Vancomycin-resistant Enterococcus
faecium (VRE) declined from 72.7% in 1995 to
5.8% in 2000. This is a bad bacteria since this is
used many times as a last resort drug.
o A superinfection results from an insufficient dosage. The antibiotic is
either overdosed or used for extended periods so that it kills the “good
bacteria,” producing resistance to the “bad bacteria.” A superinfection can
also be due to the administration of an inappropriate agent.
General guidelines for effective therapy
 Selection of the agent depends on the patient’s history, allergies, symptoms, etc.
The route of administration can be either oral (po), intravenous (IV), injection (sd,
sm), or topical (gtt). A doctor may elect to provide a combination therapy. This
means either an oral and topical or two different types of antibiotics.
 Treatment failure could indicate:
o Inaccurate diagnosis, resistance, patient non-compliance, or inadequate
physical procedures.
o The bacteria might need to be cultured first, but treatment should be
started before waiting for the results.
Mechanisms of Action
Inhibition of cell wall synthesis (so this kills the bacteria and not humans)
Penicillins (Fungi Penicillium spp.)
 Introduction
o Discovered by Flemming.


o Penicillins are beta-lactam antibiotics
 The basic structure is 6-aminopenicillanic acid, containing a betalactam ring, which is strained and therefore reactive. It is capable
of acylating several kinds of proteins. Different side chains result
in members of family with different activity spectra, sensitivities
 There exists a series of enzymes that are secreted by some bacteria
that destroy the B-lactam ring in certain penicillins. These are
termed beta-lactamases or penicillinases. Clavulanic acid or
sulbactam can be added so that the penicillin is not destroyed.
Mechanism of Action
o Penicillins act by inhibiting the synthesis of the bacterial cell wall by
interrupting the cross-linking of the polysaccharide chains that form the
peptidoglycan.
o For peptidoglycan to bind to one another, a transpeptidase needs to be
released. The penicillins bind to the transpeptidases (penicillin-binding
proteins, PBPs) and displace the terminal D-alanyl-D-alanine due to a
higher bonding affinity, irreversibly disrupting the enzyme activity by
acylating the active site. This means that the peptidoglycan chains cannot
come together to form sheets. This increases the activity of the autolytic
enzymes.
o Without cross linking of peptidoglycan, the cell wall integrity is breached.
Bacteria now very susceptible to death or damage from osmotic shock. In
hypotonic solutions, water rushes in, causing cell lysis. In hypertonic
solutions, water rushes out, but the cell can survive until conditions
change.
o It also protects against newer infections, because the defective cell wall is
actively dividing. The greatest bactericidal effect is on actively dividing
cells that are synthesizing new cell walls.
o Probenecid will lengthen the half life of all penicillins.
Mechanisms of resistance
o B-lactamases actively inactivate the antibiotic produced by bacteria by
destroying the B-lactam ring. Determinants are found on chromosomes or
plasmids.
o Change in or lack of penicillin-binding proteins (transpeptidases)
o Mutations can cause transpeptidase to function, but not bind as well.
o Failure of the drug to reach the PBP (ex. P. aeruginosa).


o Failure of the drug to bind to the PBP (ex. Methicillin-resistant S. aureus).
Sources of Penicillins
o Various species of Penicillium mold
o Semisynthetic derivatives of penicillin
Types
o Natural penicillins/ agents against gram-positive bacteria
 These penicillins are highly effective against gram-positive cocci,
some bacilli, and some gram-negative cocci and bacilli
 Subtypes
 Penicillin G
o Derived from the fungus penicillium notatum
o Good against streptococcus
o Routes of administration
 IV, IM. Usually given parenterally, but
topical preparations also available.
 Unstable in the GI system, therefore it is not
given orally.
 Penicillin V
o Synthetic derivative of Pen G, but more acid
resistant.
o Good against neisseria
o Route of administration: oral
 Uses
 This is the antibiotic of choice for systemic infections
caused by gram positive cocci (S. pneumonia, S. pyogenes,
and other strains of strep).
o It is also a great antibiotic active against gram
negative organisms, but Neisseria gonorrhoeae is
becoming increasingly resistant.
o Antibiotic of choice for treatment of syphilis caused
by the spirochete, Treponema pallidum.
 Ineffective against/resistant
o Enterococci
o Pseudomonas
o Staph aureus, because it produces a penicillinase
drug-inactivating enzyme.
 Routes of Administration
 Topical
o This is not used for minor ocular infections due to a
high incidence of allergic reactions.
 Fortified eye drops, subconjunctival injection, and IV
injection
o Reserved for major/serious ocular infections.
o Corneal ulcers caused by penicillin-sensitive Staph
and micrococci, Strep (including the
Pneumococcus), Corynebacterium, Neisseria
gonorrhoeae, Neisseria meningitides, and anaerobic
Gram negative rods.
o Penicillins resistant to penicillinase
 These have a modified penicillin structure. With an open B-lactam
ring in the penicillin molecule, it is not hydrolyzed by the
staphylococcal penicillinase. The problem is that many bacterial
strains have become resistant to these agents.
 Subtypes
 Ampicillin
o Active against G+ and G- bacteria. Acid stable.
 Cloxacillin (Cloxapen, Tegopen)
 Dicloxacillin (Dynapen)
o Good for G+ (S. aureus)
o 125, 250, and 500mg tablets
o Adult Dosage: 250-500mg qid.
o Take on an empty stomach.
o Used for hordeola, preseptal cellulitis, and
dacryocystitis (deep infections).
 Methicillin (Staphcillin)
o Less active than Pen G. Acid-labile.
 Nafcillin (Unipen)
 Oxacillin (Bactocil, Prostaphlin)
 Extended: Carbenicillin, Ticarcillin, Piperacillin, and
Mezlocillin.
o Carbenicillin is active against G- bacteria like
Pseudomonas and Proteus. Acid stable. Not well
absorbed by small intestine.
o Ticarcillin is similar to carbenicillin, but more
active against Pseudomonas.
 Uses
 Indicated in the treatment of infections caused by strains of
those that produce penicillinase (S. aureus and S.
epidermidis).
 A Penicillinase-resistant penicillin or cephalosporin is
usually used concurrently with an aminoglycoside to
provide a complementary spectrum. Aminoglycosides are
active against Gram negative rods.
 Treatment of bacterial corneal ulcers caused by Gram
positive cocci or penicillinase-resistant staphylococci.
(Methicillin or Oxacillin) This is injected
subconjunctivally.
 Treatment of severe preseptal cellulitis
o Initially IV Nafcillin or Oxacillin is used.
o If only gram positive bacteria are cultured
 Methicillin, Nafcillin, or Oxacillin

Treatment of endophthalmitis using Methicillin or
Dicloxicillin, plus an aminoglycoside.
 Treatment of hordeolum
o Penicillins with extended (wide) spectra of activity (Aminopenicillins)
 Subtypes
 Amoxicillin (Amoxil)
o This is a further modification of the basic penicillin
structure with a broader spectrum of activity.
o It is less effective against bacteria that are sensitive
to Pen G.
o Range of antimicrobial activity includes Gram
negative bacteria, H. flu, E. coli, Proteus mirabilis
o Clinical Use
 Treatment of gonococcal conjunctivitis
 URI, UTI, bacterial meningitis,
salmonella
o Dosage
 Adults: 250mg tid or 500mg bid.
 Kids: 20mg/kg/day in 3 doses or
25mg/kg/day in 2 doses.
o When combined with Clavulanate = Augmentin
 Contains a beta-lactamase inhibitor, which is
a suicide inhibitor.
 Also available in chewable tablets and oral
suspension.
 Can be taken without regards to meals.
 Dosage: Adults: 250mg tid or 500mg bid
 Good for staph resistant infections
(Sinusitis, otitis media, skin infections).
 This is expensive, but effective. It is given
when a B-lactam fails.
 Reacts with active site to irreversible inactivate B-lactamases
 Ampicillin (Amcill, Omnipen)
o If combined with Sulbactam = Unysyn.
 Contains a beta-lactamase inhibitor
 Sulbactam, like Clavulanate, is a suicide
inhibitor. B lactamase attacks this, leaving
the ampicillin.
o Bacampicillin is an ester of ampicillin.
 Adverse Effects
 Hypersensitivity reactions, GI irritation, and
superinfections (Clostridium difficile).
 Clinical Use
 Preseptal cellulitis, orbital cellulitis, and dacryocystitis.
o Penicillins with antipseudomonal activity
 Subtypes








Azlocillin (Azlin)
Carbenicillin (Geopen, Geocillin)
Mezlocillin (Mezlin)
Piperacillin (Pipracil)
Ticarcillin (Ticar).
o This can also be formulated with Clavulanate.
 Clinical Use
 Active against P. aeruginosa and certain proteus,
enterobacter, and acinetobacter species
o Effective treatment for septicemia, burn infections,
pneumonia, severe UTI, meningitis, and serious
ocular infections caused by gram negative bacteria
o Effective treatment combined with an
aminoglycoside (topical, subconjunctival, or IV) for
bacterial corneal ulcers caused by Gram negative
rods.
 Bacterial corneal ulcers caused by P. aeruginosa
Adverse effects of drugs affecting cell walls
o Essentially non-toxic. These have very little direct toxic effects.
o Hypersensitivity (5-10% of population)
 Urticaria, angioedema/anaphylaxis, hemolytic anemia, interstitial
nephritis, vasculitis, serum sickness, contact dermatitis, StevenJohnson syndrome.
 Intradermal skin tests are utilized to predict hypersensitivity.
o Non-hypersensitivity reactions caused by irritant effects produced by
excessive concentration in a small area of the body and responses to
another ingredient in the drug mixture
 Pain and sterile inflammatory reactions at site of IM injection
 Pain and dysfunction of body part innervated by peripheral nerve
accidentally injected.
 High concentration in CNS can lead to arachnoiditis, seizures, and
fatal encephalopathy
o Hyperkalemia or hypokalemia
o Dizziness (Pen G with procaine mixtures), tinnitus, headaches,
hallucinations, seizures (oral administration)
o NVD, GI upset
o Granulocytopenia
o Abnormal platelet aggregation (large doses)
o Phlebitis or thrombophlebitis (IV)
o Alterations of normal bacterial flora
o Superinfection with resistant organisms after long-term treatment
Toxicity of B-lactam antibiotic
o Usually low; high doses (10-30g/day) can be tolerated.
o Hypersensitivity found in 3-6%, which can sometimes be life-threatening.
“The Game”
o The structure with the same core needs to be constantly changed to
decrease resistance. Therefore, there is the development of semisynthetic
penicillins (e.g. methicillin with large, hydrophobic side chain resistant to
B-lactamase from staph).
o Certain strains of staph aureus have developed resistance to methicillin.
 A new penicillin-binding protein, a mutated transpeptidase, has a
very low affinity for B-lactam antibiotics. It maintains its activity,
even when B-lactam antibiotics are bound. None of the B-lactam
antibiotics are effective
 Vancomycin is the antibiotic of choice in these cases. It is used as
a last resort, since it can be fairly toxic.
Other Beta-lactam Antibiotics
 Imipenem
o Rapidly hydrolyzed by the kidney. This is inhibited by the addition of
cilastatin (Primaxin)
o Adverse effect: Allergic reactions (cross-sensitivity with penicillins and
cephalosporins)
 Meropenem- Similar to imipenem, but not hydrolyzed by the kidneys.
 Aztreonam (Azactam)
o Similar to imipenem, with no cross-sensitivity with penicillins or
cephalosporins
Cephalosporins (Fungi Cephalosporium spp.)

Background
o This has a similar mechanism of action to penicillin. It interferes with the
terminal step in the bacterial cell wall formation by preventing proper
cross-linking of peptidoglycan. This alters the bacterial permeability,
inhibiting protein synthesis, causing release of autolytic effects, and
therefore preventing bacteria cellular division.

o It is yet another category of beta-lactam antibiotics with variable
susceptibility to B-lactamase. Some cephalosporins are resistant to most
B-lactamases. None are resistant to all B-lactamases
Types: Available as 1st, 2nd, 3rd, and 4th generation compounds based on the
spectra of bacterial activity and clinical uses. In general, progression from first to
fourth generations reveals broader Gram negative spectrum and loss of efficacy
against gram positive organisms.
o First generation cephalosporins
 Spectra of activity
 Good against Gram positive bacteria, with a relatively
modest activity against Gram negative bacteria. It is useful
against most Strep forms and S. aureus (narrow spectrum).
 Sensitive to inactivation by B-lactamase produced by Gram
negative bacteria.
 Clinical Use
 Surgical prophylactic procedures (cardiovascular,
orthopedic, head/neck, gastroduodenal, biliary tract, and
gynecologic).
 Also used for hordeola, dacryocystitis, preseptal cellulitis,
and orbital disease.
 Types
 Cefadroxil (Duricef, Ultracef)
o Good for skin infections
o Dosage
 Available in 500mg capsules and 1000mg
tablets, as well as an oral suspension.
 Adults: 500-1000mg/day q12h
 Kids: 30mg/kg/day q12h
 Can be taken without regard for meals
 Cephalexin (Keflex)
o Good for preseptal cellulitis and dacryosistitis.
o Dosage
 Available in 250 and 500 mg tablets and
capsules, as well as an oral suspension
 Adults: 250mg q6h
 Kids: 25-50mg/kg/day in divided doses
 Can be taken without regard to meals
 Cephapirin (Cefadyl)
 Cephalothin (Keflin)
 Cephazolin (Ancef, Kefzol)
o At one time this was the drug of choice for bacterial
corneal ulcers. The spectrum of activity covers
Penicillinase, R staph, Proteus mirabilis, Strep, S.
pneumoniae, and E. coli. It possesses greater
activity against Staph and Strep. It is still used with
caution in patients who are allergic to penicillin.
o More water soluble (important in fortified solution)
so it can increase the concentration.
o Route of administration
 Topically as fortified eyedrops
 Subconjunctival injections
 Cephradine (Anspor, Velosef)
o Second generation Cephalosporins
 Useful against a wider spectrum of organism. It is more active
against Gram negative enteric bacteria than 1st generation, but less
active than the 3rd. There are few clinical applications because of
its mediocre activity.
 It is active against beta lactamase producing H. flu and more
resistant to Cephalosporinase.
 Types
 Cefaclor (Ceclor)
o Used for treating internal hordeola and preseptal
cellulitis.
o Dosage
 Available in 250 and 400mg capsules
 Adults: 250mg q8h
 Kids: 20mg/kg/day q8h.
 Can be taken without regard for meals.
 Cefamandole (Mandol)
 Cefonicid (Monocid)
 Ceforanide (Precef)
 Cefotetan (Cefotan)
 Cefoxitin/ Ceftizoxime (Mefoxin)
 Cefuroxime (Kefurox, Ceftin)
o Third Generation Cephalosporins
 This is useful against an even wider spectrum of organisms,
including Gram negative organisms, than the previous two
generations. It is less active against Gram positive organisms and
more resistant to cephalosporinase.
 Good for gonorrhea and UT infections.
 Types
 Cefixime (Suprax)
 Cefoperazone (Cefobid)
 Cefotaxime (Claforan)
 Ceftaxidime (Fortaz)
o Used topically, subconjunctivally and intravenously
for endophthalmitis caused by P. aeruginosa.
 Ceftizoxime (Cefizox)
 Ceftriaxone (Rocephin)
 Cephtizoxime (Cefizox)
o Fourth generation


This has the same spectrum as third generation, but it is more
resistant to most beta-lactamases. It is also as effective as
Ceftaxidime against P. aeruginosa.
 Subtypes
 Cefepime for “hospital acquired” infections
 Cepirome
Adverse effects
o Hypersensitivity (cross-sensitivity with penicillins)
 Maculopapular rash, urticaria, fever, itching, bronchospasm,
anaphylaxis, eosinophilia.
 5-20% cross-reactivity to penicillin, so it is used with caution in
patients with known allergies to penicillin. Differences from
penicillins suggest that there might be little or no cross-reactivity
for penicillin-sensitive patients, but this is not entirely true.
o Alteration in normal microflora, causing anorexia, nausea, vomiting, and
diarrhea, which may be severe.
o Antibiotic-associated pseudomembranous colitis due to Clostridium
difficile superinfections. It can also be due to Pseudomonas, candida, and
enterococci
o Vitamin K deficiency leading to bleeding.
o Reversible renal impairment. There is an additive nephrotoxicity when a
cephalosporin is used in combination with an aminoglycoside.
o CNS problems (HA, dizziness, and fatigue)
Vancomycin
 Mechanism of action
o Inhibits biosynthesis of peptidoglycan during bacterial cell wall formation.
It binds to the terminal alanine of the pentapeptide (D-alanyl-D-alanine)
on the cell wall precursor unit, preventing further attachment by sterically
blocking elongation of the peptidoglycan.
 Mechanisms of resistance
o Some cells are impermeable to the compound. Others lack autolytic
enzymes required to lead to cell death.
o New resistance seen in staph (VRSA)
 Apparent alternative pathway with D-alanyl-D-phenylalanine
rather than D-alanyl-D-alanine terminus. This is done with
transpeptidases.
 Determinants found on chromosome and plasmids.
 Not much VRSA, but some reported.
 No outbreaks yet, but can happen.
 Clinical use
o Bactericidal antibiotic with complex glycopeptide structure. Narrow
spectrum. Highly active against Gram-positive cocci (staph, strep),
Clostridium, corynebacterium diphtheriae, N. gonorrhoeae, and moraxella.
o Reserved for serious infections because of its toxicity. It is a last resort
drug. Some resistance is encountered.


o As of single entity or in combination with an aminoglycoside is useful in
treating bacterial endocarditis.
o Alternative to penicillins or cephalosporins for the treatment of serious
infections caused by staph, strep, enterococci, and clostridium.
o Used in serious infections where the B-lactam antibiotics have been ruled
out/ Last resort.
o Drug of choice for treating infections caused by methicillin resistant staph,
especially endophthalmitis (i.e. blepharitis caused by a methicillinresistant strain of S. epidermidis).
o Drug of choice for treating pseudomembranous colitis caused by
Clostridium difficile
Dispensing Information
o 10mg/ml
o 1mg/0.05-0.1ml- Final concentration (IV concentration reduced to
10mg/ml)
o Recon: 0.5g vial with 10 ml sterile water (500mg with 10ml solution)
Adverse effects
o Toxic with oral administration, especially with long-term use.
o Fever
o Ototoxic- permanent deafness can occur. It destroys the hair cells in the
inner ear, causing hearing loss. Rare.
o Dizziness
o Nephrotoxic- fatal uremia
o Red man syndrome- systemic red rash.
o Possible to use iron chelators to overcome the side effects.
Bacitracin (Bacteria Bacillus spp.)
 Mechanism of action
o Inhibits bacterial cell wall synthesis at a selectively different step in the
process than penicillin. With zinc, it prevents the formation of
polysaccharide chains which are needed to form the cross linkage in the
peptidoglycan of the cell wall. This blocks the dephosphorylation
(regeneration) of isoprenyl alcohol phosphate, which carries Nacetylmuramul peptide and N-acetylglucosamine across the cell
membrane.
o Bactericidal against gram positive organisms (staph, strep, clostridium
difficile, moraxella), but inactive against gram negative organisms.
 Mechanism or resistance
o Decreased access of antibiotics to cell
 Clinical uses
o Primarily used topically to treat skin and mucous membrane infections by
gram positive bacteria.
o In combination- Ulcers, external otitis, sycosis, superficial folliculitis, and
impetigo
o Ophthalmic uses include suppurative conjunctivitis, blepharitis, and
infected corneal ulcers


o It is rarely used today as an oral agent.
Dosage
o Stable only in ointment form- 500 U/gram, qd to bid
o Available as a single entity product or as a component of a fixedcombination product with polymyxin B (Polysporin) and neomycin
(termed Triple antibiotic ophthalmic ointment). Available OTC.
Adverse effects.
o Very few. Mainly contact dermatitist
o Severe nephrotoxicity
Cycloserine
 Rarely used today because it is highly toxic.
 Broad spectrum, bactericidal
 Mechanism of action
o This is a structural analog of D-alanine, so it inhibits the action of alanine
reacemase and D-alanyl-D-alanine synthestase.
 Mechanisms of resistance
o Loss of D-alanine permease prevents cycloserine from entering cells. The
clinical relevance is uncertain.
Teichoplanin
 Mechanism of action: Blocks polymerization of the peptidoglycan chain.
Antibacterial Drugs Affecting the Bacterial Cytoplasmic Membrane
Polymyxin B
 Oral Agents
o Polymyxin B (Aerosporin)
o Colistin (Coly-mycin S)
 Mechanism of Action
o Interact with the phospholipids of the cells membranes via detergent
action (cationic), disrupting the osmotic integrity of the cell. Ultimately,
this increases the bacterial cells permeability and causes leakage of
intracellular molecules.
o Bactericidal
o Poor systemic absorption because it does not penetrate blood-brain barrier.
 Clinical use
o Poor absorption due to the fact that it does not penetrate the blood-brain
barrier
o Topically on eye in combination with other antibiotics for infections of
anterior segment, e.g. Polysporin, Neosporin, and Polytrim with
Trimethoprim
o Dose: 10,000 units/g or ml
o Highly active against gram negative bacteria, but limited use due to
toxicity


o Current systemic indications for serious infections caused by strains of P.
aeruginosa that are resistant to the antipseudomonal penicillins, the 3rd
generation cephalosporins, and the aminoglycosides.
o Useful in the prevention and treatment of skin infections and external
otitis.
o Polymyxin B is available alone as an ophthalmic preparation, in
combination with other antibiotics (ointment or suspension), as well as
with steroids (ointment or suspension).
 Uses of topical polymyxin B alone include cutaneous
Pseudomonas infections, bacterial conjunctivitis, corneal
abrasions, and epithelial microcysts
 Oral colistin alone treats diarrhea in children.
Ocular indications
o Effective for the treatment of common bacterial infections of the
conjunctiva and lids.
o Recommended topical dosage for the treatment of bacterial conjunctivitis
 Antibacterial combination (Polytrim and Polysporin) used every 24 hours for 2-3 days or until controlled, then tapered to qid for an
additional week.
o Used in the treatment of corneal ulcers caused by P. aeruginosa (topical
application or subconjunctival injection). However, drugs of choice are
penicillins or aminoglycosides for this condition.
Adverse effects
o From systemic administration (IV). Don’t give via IV.
 Neurotoxicity characterized by dizziness, vertigo, ataxia, blurred
vision, confusion, paresthesias, and numbness/weakness/paralysis
of the extremities.
o Nephrotoxicity 20%
 1-2% develope tubular necrosis.
o From topical application
 Irritation and allergic reactions of the eyelids and conjunctiva
o From subconjunctival injection
 Pain, chemosis, and tissue necrosis.
Gramicidin
 Similar to polymyxin B and colistin in that it alters the permeability
characteristics of the bacteria cell membrane, killing the cell, yet unlike
polymyxin B and colistin, gramicidin is effective against gram positive bacteria
and available in solution.
 Available only as commercial preparation and polymyxin B and neomycin
(Neosporin eyedrops, not ointment).
Inhibitors of protein synthesis
Aminoglycosides (Bacteria Streptomyces spp.)





This is a very good bacteriocide.
Mechanism of Action
o Bind irreversibly to the 30S subunit of the ribosome, inhibiting the
initiation of mRNA step of translation. This affects the amino acyl tRNA
attachment or blocks the peptidotransferase or translocation. It produces
the wrong amino acid. The key is the difference between bacterial and
eukaryotic ribosomes.
Mechanism of Resistance
o Gram-negative bacilli may secrete enzymes that inactivate
aminoglycosides, causing resistance. These are plasmid-mediated which
can lead to chemical modification of the antibiotic and mutation of
ribosomal proteins. The metabolite sometimes blocks uptake of the drug
into bacterial cells. Penicillins inactivate aminoglycosides if mixed
together.
o The resistance is achieved by either due to enzymatic metabolism of the
aminoglycoside by the bacterial cell (the most common method), due to
alteration of ribosomes (therefore no binding), or due to inadequate
transport of the aminoglycoside into the bacterial cell.
o Cross-resistance exists
Clinical Uses
o Highly effective against infections caused by gram negative bacilli
(Pseudomonas, proteus, klebsiella, E. coli, enterobacter, serratia, and some
gram positive organisms, many strains of staph). Strep can be resistant.
o However, not frequently used for systemic staphylococcal injections
because there are alternative antibiotics which are equally effective and
less toxic. Neomycin is the exception.
o Systemic administration must be by the parenteral route due to poor
absorption from the GI tract
o Aminoglycosides must be administered separately from penicillins to
avoid inactivation.
Adverse effects (from systemic administration)
o Ototoxicity





Auditory dysfunction/cochlear damage characteristics- Tinnitus
and sensation of pressure of fullness in the ears. (Kanamycin and
Amikacin)
 Vestibular dysfunction manifestations- Nystagmus, vertigo,
nausea, vomiting, acute Meniere’s syndrome. (Streptomycin and
Gentamicin)
o Nephrotoxicity- Acute tubular necrosis
o Neuromuscular blockage characteristics
 Respiratory depression and possible cardiac arrest, dilated pupils,
generalized muscular weakness of the extremities, paralysis of the
EOMs, and ptosis.
o PTC with secondary papilledema (from systemic administration of
gentamicin)
o Allergic reactions
Contraindications
o Use caution with MG patients as they are more susceptible to potential
neuromuscular blocking action, which may cause respiratory failure.
o Binds with iron in the blood, producing free radicals. Leads to hair cell
destruction in the inner ear, producing deafness. Use iron chelators to stop
the side effects.
Types
o Streptomycin*, kanamycin*, neomycin*, tobramycin, gentamycin,
amikacin, spectinomycin, etc.
 *Particularly toxic and no longer used.
Streptomycin
o Bactericidal against aerobic gram-negative bacilli and certain
mycobacteria.
o Indicated for the treatment of bacterial endocarditis, tularemia, plague, and
tuberculosis (most serious form). This is usually the second choice
aminoglycoside. Many organisms are resistant
Neomycin (Mycifradin)
o This is the most toxic aminoglycoside antibiotic. It is broad spectrum and
active against gram positive organisms. Pseudomonas is resistant.
o Routes of Administration
 Oral administration- Employed to prepare the bowel for surgery
and used as an adjunct to hepatic coma therapy.
 Parenteral administration- Few to no indications.
 Topical administration (Most common form)
 Available in combination with other antibiotics or steroids
in ophthalmic, otic, and dermatologic preparations (i.e.
Neosporin with polymyxin)
 Indicated for skin and mucous membrane injections
o Dosage- Q3-4hours.
o Side effects
 Topical ocular application (not recommended)



Sensitization occurs frequently. 4% develop contact
dermatitis of lids and conjunctiva.
 Bacitracin-polymyxin B preferred
Gentamicin (Genoptic, Garamycin)
o Highly active against
 Serious gram negative bacillary injections, staph, and H. flu
 Most strains of staph, not strep.
 Pseudomonas
o As effective as a combination of neomycin, bacitracin, and polymyxin B.
o Clinical Use
 Systemically
 Complicated UTI, pneumonia, meningitis, peritonitis,
gonorrhea
 Topical indications
 Dermatologic preparations- Infected burns,
 Ophthalmic solution and ointment- Conjunctivitis,
blepharitis, keratoconjunctivitis, dacryocystitis, and
bacterial endophthalmitis.
 Aminoglycoside of choice for the initial treatment of
bacterial infections of the external eye.
 For the initial treatment of bacterial corneal ulcers- Used in
combination with a penicillinase-resistant penicillin or
cephalosporin
 Specific treatment fortified drops for pseudomonas corneal
ulcers
 Used in combination with a penicillin having
antipseudomonal activity (i.e. carbenicillin or ticarcillin)
 Initial treatment of choice for traumatic endophthalmitisUsed in combination with a cephalosporin or a penicillinase
producing staphylococci resistant penicillin (systemically,
topically, subconjunctivally, or intravitreally)
o Recommended dosage
 Mild to moderate infections
 1-2gtt solution every 4 hours
 ¼” ribbon ointment, bid-tid x 7-10days.
 Severe infections- up to 2 drops every hour.
o Adverse effects
 Minor irritation, punctate epithelial keratopathy, delayed wound
healing, corneal ulceration, pseudomembranous conjunctivitis,
focal bulbar conjunctival hyperemia, periocular skin and
conjunctival paresthesia, lid edema, itching, sensitization (50% of
patients allergic to neomycin become allergic to gentamicin), and
necrosis.
Tobramycin (Tobrex, Tobrasol, AK-Tob)




o Antibacterial activity and pharmacokinetic properties essentially identical
to gentamicin, except tobramycin is not effective against N. gonorrhea.
More effective against P. aeruginosa infections.
o Less toxic than gentamycin when injected into the vitreous, thus strongly
indicated for the treatment of bacterial endopthalmitis
o Cross-resistance between gentamycin and tobramycin for Klebsiella,
enterobacter, E. coli, and serratia. Amikacin highly active against the
above resistant strains
o Clinical Uses- anterior segment disease.
o Dosing
 Available as topical ophthalmic solution, topical ophthalmic
ointment, and powder for parenteral administration.
 Qh-qid for solution
 Bid-q4h for ung.
 Pregnancy category B, so can be used.
o Side effects
 From topical administration
 Reversible tearing, burning, photophobia, eyelids edema,
conjunctival hyperemia and chemosis, and punctate
epithelial erosions.
 This has the least amount of side effects of
aminoglycosides.
Amikacin
o First semisynthetic aminoglycoside
 Resistant to aminoglycoside-inactivating enzymes
o Preferred drug for the treatment of infections caused by gram negative
bacilli that are resistant to other aminoglycosides.
o Used as a primary drug (in combination with a cephalosporin) for the
treatment of bacterial endophthalmitis. Injected intravitreally.
o Drug of choice in treating corneal ulcers caused by mycobacteria.
Kanamycin
o Limited spectrum of activity. It is not effective against pseudomonas and
most gram positive bacteria. There is increasing resistance.
o Similar to neomycin
o Clinical Use- Involved in preparing the bowel for surgery and used as an
adjunct to hepatic coma therapy.
Spectinomycin
o Used only to treat penicillin-resistant gonorrhea
Netilmicin (Netromycin)
Tetracyclines (Bacteria Streptomyces spp.)




Background
o Bacteriostatic in low concentration and bacteriocidal in high
concentrations.
o Anticollagenolytic properties demonstrable.
o Accumulate within oil-producing glands and reduce lipase activity.
o Binds to ions (Fe, Ca, Mg, Al).
o Needs a low pH to be absorbed.
o Broad spectrum including several protozoans
o Can also be paired with agents to alter membrane permeability to inhibit
fungal and mammalian cell growth.
o Not typically used against common bacterial infections
Mechanism of Action
o Attach to the 30S subunit, preventing attachment of aminoacyl-tRNA to
the acceptor site on mRNA-ribosomal complex
o Inhibit protein synthesis in human cells as well as in microorganisms,
however, greater degree of protein inhibition is produced in
microorganisms due to the fact that they exhibit active transport while that
of mammalian cells is passive. This is because there is antimicrobial
activity against normal bacterial flora in addition to pathogenic
microorganisms.
Mechanism of resistance
o Active efflux- use energy to pump the Ab out.
 Chromosomal or plasmid-mediated.
o Resistance
 S. aureus (>1/3) and Pseudomonas aeruginosa.
 Seen more with tetracycline, because it has been around awhile.
 Declining number of clinical indications due to this increasing
resistance.
Types- Three classes based on their half-lives.
o Short-acting analogs (half-life 6-9 hours)
 Tetracycline (Achromycin)
 250 and 500mg capsules and tablets.
 1% tetracycline suspension and ointment
 Cheap
 Chlortetracycline (Aureomycin)
 1% chlortetracycline ointment- fixed combination ointment
 Oxytetracycline (Terramycin)
 Oxytetracycline and polymyxin B ointment

o Intermediate-acting analogs (half-life 9-17 hours)
 Methacycline (Rondomycin)
 Demeclocycline (Declomycin)
o Long-acting analogs (half-life 17-20 hours)
 Doxycycline (Vibramycin)
 50-100mg capsules and tablets.
 Dosage generally 100mg qd or bid if >8 years. Length of
therapy varies with severity of condition. Taper with
improvement.
 Can be taken without regards to meals because does not
bind ions.
 More expensive
 Less toxic.
 Minocycline (Minocin)
 Absorption from gut impeded by cations in gut.
Clinical uses
o Useful spectra: broad spectrum
 Gram positive (best affinity) and negative, as well as aerobic and
anaerobic bacteria
o Drugs of choice for
 Brucellosis
 Rickettsial infections
 Rocky mountain spotted fever, typhus, and Q-fever
 Mycoplasma pneumonia
 Cholera
 Plague
 Urea plasma urethritis
 Chlamydial infections
 Venereal disease, trachoma, and inclusion conjunctivitis
 Recommended dosage- 250mg qid x3 weeks.
 Doxycycline- initial loading dose of 200mg, followed by
100mg daily for 2 weeks (except for Chlamydia 100mg bid
x 2 weeks)
o Ophthalmic Uses
 Recommended by CDC as an effective alternative to silver nitrate
for prophylaxis of gonococcal ophthalmia neonatorum (ointment)
 Recalcitrant cases of nontuberculous phlyctenular
keratoconjunctivitis dosage regimen
 250mg bid to tid until 3 weeks after patient becomes
asymptomatic then tapered down to maintenance dose
 Sterile corneal ulcers- 250mg qid
 Persistent epithelial defects- 250mg qid
 Ocular manifestations of acne rosacea
 Tetracycline- 250mg qid reduced by 1 daily dose after
every month of therapy followed by discontinuation or
lowest maintenance dose. Dose up to 6 weeks.



Therapeutically effective against acne vulgaris by reducing
the free fatty acids in the sebum.
 Also for blepharitis, meibomitis, and resistant sebaceous
blepharitis.
Adverse effects
o Tetracyclines bind to calcium, iron, magnesium, and aluminum in foods,
so they must be given between meals when administered orally. Adverse
effects on absorption occur when taken with
 Dairy products, iron-containing tonics, antacids containing
calcium, magnesium, or aluminum, and sodium bicarbonate.
 Simultaneous administration of the above with tetracyclines need
to be restricted.
 It is best that this is taken on an empty stomach. (1 hour before and
2 hours after a meal).
o Gastrointestinal irritation characterized by cramping, anorexia, heartburn,
N, V, flatulence, and diarrhea (if persistent or severe, consider
pseudomembranous colitis caused by clostridium difficile). This is the #1
complaint.
o Hypersensitivity reactions characterized by anaphylaxis, urticaria,
periorbital edema, and morbilliform rashes.
o Photosensitivity manifested by exaggerated sunburn reaction.
o Alters renal function demonstrated by negative nitrogen balance, increased
blood urea nitrogen (BUN) levels, and possible azotemia. Doxycycline
does not disrupt renal function, because it is excreted through the intestinal
tract.
o Liver dysfunction (associated with IV administration of >2g)
o Depresses bone growth and discolors teeth by attaching to embryonic and
growing bone tissue, forming a tetracycline-calcium orthophosphate
complex. This causes changes in both deciduous and permanent teeth
during development, manifested by dysgenesis, staining, (yellow/brown
bands), and increased propensity to develop caries.
o PTC
o Blood dyscrasias- Hemolytic anemia, thrombocytopenia, neuropenia, and
eosinophilia
o Vestibular toxicity (unique to minocycline) characterized by light
headedness, loss of balance, dizziness, nausea, and tinnitus.
o Drug interactions with coumarin-type anticoagulants, penicillins
(parenteral administration), carbamazepine (Tegretol),
diphenylhydraritoin, and barbiturates.
Contraindicated use
o During the last half of pregnancy
o Lactating women
o Children under 8 years of age.
o Long-term
Chloramphenicol (Bacteria Streptomyces sp. Chloromycetin or Chloroptic)





Broad spectrum, bacteriostatic for all species except Neisseria and Haemophilus
(bactericidal) and Pseudomonas and Proteus (insusceptible)
Rarely used now
Mechanism of action
o Bacteriostatic
o Inhibits protein synthesis by binding reversibly to the 50S subunit of the
bacterial ribosome and blocking peptidyl transferase. Can also act on the
30S
o No effect on 80S eukaryotic ribosome; effective against 70S prokaryotic
ribosome
 Also effective against 70S mitochondrial ribosome
 At certain sites, may not have access or inhibition of
mitochondria may not be of consequence.
Mechanisms of resistance
o Chloramphenicol acetyltransferase. Acylates it, rendering it inactive
o Decreased permeability
 Plasmid-mediated
Clinical uses
o Lipid soluble, therefore readily penetrates the blood-brain barrier and
blood-aqueous barrier.
o Very broad antibacterial spectrum. Highly active against most gram
positive and gram negative bacteria, rickettsia, Chlamydia, spirochetes,
mycoplasma, and possibly pseudomonas aeruginosa.
o Indicated for severe of life-threatening infections not responsive to other
agents, including acute typhoid fever and salmonella infections
(bacteremia).
 Systemically- endophthalmitis following penetrating trauma and
topically- ocular bacterial infections not responsive to less toxic
antibiotics.
 Limited to the treatment of intraocular infection such as
endophthalmitis following penetrating trauma or surgery.
However, drug of choice to treat intraocular infections is
penicillinase-resistant PCN or cephalosporin combined with an
aminoglycoside.
o Preferred antibiotic for CNS infections
 Bacteroides infections- B. fragilis
 Meningitis caused by N. meningitides, S. pneumoniae, and H. flu
(especially in cases of ampicillin resistance).
 If allergic to penicillin.
o Reserved for infections outside the CNS caused by H. flu that are
ampicillin-resistant.
o This is often a last resort medication.



Available in both an ointment and solution.
Adverse effects
o Reversible bone marrow depression. Potentially fatal.
o 2 types of hematopoietic abnormalities
 Dose-related toxic effect causing aplastic anemia (a reversible
bone marrow depression, >6g/day or serum levels >25
microgram/ml). Pancytopenia with an aplastic marrow is the most
severe presentation of aplastic anemia.
o Gray Baby Syndrome
 A toxic reaction occurring in premature infants and neonates
whereby a high plasma concentration of chloramphenicol develops
because the immature liver’s ability to detoxify the drug or the
immature kidney’s inability to excrete the active form of the drug.
 Characterized by abdominal distention, vomiting, flaccidity,
cyanosis, circulatory collapse, and death.
 Chloramphenicol is not recommended to infants during the 1st 2
weeks of life.
o Confusion, depression
o Optic neuropathy, dense central scotomas, and retinal edema.
o NVD
o Enterocolitis
o Important: although chloramphenicol is used in other countries, the
consensus among American ophthalmologists and optometrists is that
there are no good ocular indications to use this drug.
o Also inhibits mitochondrial ribosomes.
Contraindications
o Don’t use in patients less than 24 years.
Macrolides
 Broad spectrum. Gram positive (staph, strep) cocci, neisseria, and Chlamydia
 Bacteriostatic (cidal with increased concentrations.)
 Mechanism of action
o Bind to the 50S subunit of the ribosome, preventing amino acid
attachment.
o Resistance develops due to synthesis of modified ribosomes.
 Erythromycin (Bacteria Streptomyces spp.)
o Bacteriostatic, most active against Grap + bacteria, 2 gram negative
genera, Neisseria and Haemophilus, and several anaerobes.
o Effective against Mycoplasma pneumoniae, Bordatella pertussis, and
Legionella.
o Semisynthetic macrolides, azithromycin, and clarithromycin have
advantages
 The second generations are more stable, have decreased toxicity,
and increased spectrum of action.
 Effective against some opportunistic pathogens of AIDS patients.
o Major alternative for patients with PCN sensitivity (1st option)
 Effective against PCN-resistance bacteria.
o Types
 Erythromycin (Erycette, many others)- First developed
 Erythromycin base (E-Mycin, Ilotycin)
 Erythromycin base stearate (Erypar)
 Erythromycin base estolate (Ilosone)
 Not the 1st choice due to side effects
 Erythromycin base ethylsuccinate (EES) - best choice because can
be taken without regard to meals.
o Low toxicity
 Does not inhibit protein synthesis in human cells like tetracyclines.
o Mechanism of action
 Binds to P site of 50S subunit to inhibit translocation.
 Can inhibit 70S ribosomes of mitochondria but does not cross
mitochondrial membrane.
o Mechanism of resistance
 Decreased permeability (chromosomal mutation
 Mutation of ribosomal protein (plasmid-mediated or chromosomal
mutation), so decreased binding.
o Clinical uses
 Drug of choice for
 Legionnaires disease (legionella pneumophila)
 Primary atypical pneumonia (Mycoplasma pneumoniae)
 Diphtheria (in combination with diphtheria antitoxin)


Acute, symptomatic campylobacter enteritis
Prophylactic regimen for colorectal surgery (in
combination with neomycin).
 Alternative drug to penicillin for the treatment of streptococcal
infections
 Pharyngitis, scarlet fever, cellulitis, erysipelas (Strep
pyogenes), pneumonia and bronchitis (strep pneumoniae),
prophylaxis of rheumatic fever recurrences, prevention of
endocarditis resulting from dental procedures, acute otitis
media (S. pneumoniae or S. pyogenes), otitis media (H. flu)
in children (in combination with a sulfonamide, however,
drugs of choice are penicillinase-resistant penicillins and
cephalosporins), anthrax, actinomycosis, Listeria
infections, certain anaerobic infections, syphilis and
gonorrhea.
 Dosage
 Topical and oral formulations.
 Adults and kids: 250-500mg qid x 3 weeks.
 Can be qd-prn
o Ocular uses
 Staphylococcal infections of the eyelid
 ¼-1/2” ribbon of erythromycin ointment qhs or more often
if severity warrants
 Adjunctive therapy before application includes warm
compresses for 5 minutes and gentle lid scrub and dilute
baby shampoo.
st
 1 drug of choice for treating Chlamydia trachomatis infections in
infants and children
 Safer use in pregnant women, nursing mothers, and
children under 8 years of age.
 Gonoccal/ Chlamydial ophthalmia neonatorum
o Oral dosage: 25mg/kg body weight every 12 hours
for at least 2 weeks.
o 0.5-1.0 cm ribbon of erythromycin ointment applied
to each conjunctival sac.
 Alternative drug to tetracycline for the treatment of
chlamydial venereal disease, trachoma, and inclusion
conjunctivitis
o Oral dosage for adults and older children: 250mg or
333mg qid for 2-3 weeks.
o Side effects
 One of the safest antibiotics. ADRs are generally mild. Pregnancy
category B
 Side effects from oral administration
 Pseudomembranous colitis (rare)
 Cholestatic hepatitis (most serious toxicity)


o Occurs only when erythromycin estolate is given. It
prevents the bile flow. This is mainly in adults.
o Characterized by N, V, and abdominal pain,
followed by jaundice, fever, and abnormal liver
function tests.
 GI irritation, so should be taken on an empty stomach. This
can also be caused by enteric coated tablets and ester
derivatives that allow the medicine to be taken with food,
e.g. ethylsuccinate. GI upset can be reduced or eliminated
by taking erythromycin with food and using the
ethylsuccinate or stearate form of erythromycin.
 Nausea, vomiting, pyrosis, and diarrhea.
 Headache, dizziness, and fatigue.
 Topical side effects include mild allergic reactions manifested as
urticaria and other rashes, fever, and eosinophilia
 Sensorineural hearing loss (extremely rare)
 Improves with discontinuation.
o Drug interactions
 Erythromycin may increase blood levels of Terfenadine (Seldane)
and Astemizole (Hismanol), leading to serious cardiac toxicity
(Torades de Pointes), therefore, do not prescribe to patients taking
these non-sedating antihistamines.
 Interferes with elimination of theophylline with caffeine.
 Increases the blood levels of digoxin, eryotamine, cyclosporine,
and warfarin, enhancing anticoagulant activity.
 Avoid prescribing to patients taking antifungals.
 Contraindicated in those with liver dysfunction/alcoholics.
Azithromycin (Zithromax)
o A macrolide with an extended half-life (40-86 hr), therefore once daily
dosing is effective.
o More active against gram negative bacteria (H. flu and Moraxella)
o Used for respiratory infections and for Chlamydia conjunctivitis.
o Usual dosage: Z-Pak- 500mg first day, followed by 250mg days 2-5.
o A single 1g dose of Zithromax is effective to treat Chlamydia, but is
expensive.
o Topical forms not available
o Side effects
 Similar to erythromycin: diarrhea, nausea, abdominal pain. Also,
palpitations, vaginitis, headache, and dizziness.
 Take on an empty stomach.
Clarithromycin (Biaxin)
o Another macrolide with long half-life, so patients can take meds bid.
o Stable in acid.
o More active than erythromycin against Chlamydia, but less active than
azithromycin.
o Active against H. flu. Also good against sinusitis and H. pylori. Used for
infections caused by nontuberculous mycobacteria.
o Usually dose: 250-500mg bid x 7-14 days.
o Topical forms not available.
o Side effects
 This has the most side effects of all macrolides.
 In order: N, V, taste perversion, abdominal pain, rash, diarrhea,
and HA. Teratogenesis.
Mixed-Combination Drugs
 Cortisporin
o Ointment
 Polymyxin B-bacitracin-neomycin-hydrocortisone
 Dosage- qd to qid
o Suspension
 Polymyxin B-neomycin-hydrocortisone
 Dosage: 1-2 drops q1-6 hours depending on the severity
o Ocular indication
 Inflammatory conditions of palpebral and bulbar conjunctiva,
cornea, anterior segment
 Corneal injury from chemical, radiation, or thermal burns, as well
as penetrating foreign body.
 Tobradex
o 0.1% dexamethasone and 0.3% tobramycin
o Dosage
 Suspension- 1-2 drops instilled in the cul de sac every 4-6 hours.
During the first 24-48 hours, dosage may be increased to 1-2 drops
every 2 hours.
 Ointment- apply a small amount (1/2” ribbon) to the cul de sac up
to 3-4 times daily.
o Ocular indications
 For steroid responsive inflammatory ocular conditions for which a
corticosteroid is indicated and where superficial bacterial ocular
infection or a risk of bacterial ocular infection exists.
 Maxitrol
o Neomycin sulfate-polymyxin B-dexamethasone
o Dosage
 Ointment- qd-qid
 Suspension- 1-2 drops q1-6hours depending on severity
 Neosporin
o Ocular indications- Superficial external ocular infections.
o Ointment
 Polymyxin B-bacitracin-neomycin
 Dosage- Apply q3-6hours x7-10 days
o Suspension
 Polymyxin B-neomycin-gramicidin


Dosage- 1-2 drops bid to qid x7-10days
Polysporin
o Polymyxin B-bacitracin
o Dosage- Apply q3-6 hours for 7-10 days
o Mixed combination ointment of choice when steroid is not needed.
Clindamycin (Cleocin)
 Mechanism of action
o Binds to the 50S ribosomal subunit and inhibits protein synthesis
o Primarily bacteriostatic
o Resistance develops due to synthesis of modified ribosomes.
 Clinical uses
o Gram positive and anaerobic gram negative.
o Treatment of infections outside the CNS that involve B. fragilis or other
penicillin-resistant anaerobic bacteria
o Alternative treatment modality for infections caused by clostridium
perfringens and actinomyces Israeli.
o Intraabdominal infections, gynecologic/pelvic infections, anaerobic
bronchopulmonary infections, acne.
o In combination with aminoglycoside, it is useful in colorectal and urologic
surgical procedures.
 Ocular indications
o Treatment of active, recurrent ocular toxoplasmosis (eradicates encysted
Toxoplasma gondii in ocular tissues preventing recurrent episodes) and
toxoplasmic retinochoroiditis in combination with sulfadiazine or alone.
This is not currently approved by the FDA for this treatment.
 Dosage
o Po, iv, im
 Side effects
o GI upset-severe diarrhea
o Fatal pseudomembranous colitis from an overgrowth of clostridium
difficile. Treat this colonic deposition with Vancomycin.
o Hypersensitivity reactions (pruritis, rash, and urticaria).
o Transient alteration in liver function (not to the degree of hepatotoxicity).
Inhibitors of nucleic acid synthesis
Fluoroquinolones (Quinolones)





Background
o Most commonly used
o Modifications of original quinolones have yielded 6-fluoroquinolones with
reduced toxicity.
 Ciprofloxacin and norfloxacin
o Greater potency. Bacteriostatic.
o Broad spectrum antibiotic against aerobic and facultative anaerobes.
Active against most gram negative bacteria including pseudomonas, H.
flu, and many gram positive bacteria including staph and some anaerobes.
Mechanism of action
o Inhibits DNA synthesis during bacterial replication by preventing the
action of DNA gyrase activity and this inhibition kills the bacteria. DNA
gyrase enables the supercoiling, nicking, and resealing of bacterial DNA
needed for replication.
 Bacterial DNA gyrase at least 100-fold more sensitive than is
mammalian topoisomerase II.
 Mutagenic for bacteria; no evidence for animals
Mechanisms of resistance
o Bacterial resistance is low due to rapid kill rate (low MIC90), although
strains are becoming resistant.
o Decerased permeability
o Reduced sensitivity of DNA gyrase
Clinical Use
o Effective treatment of ocular bacterial infections, such as moderate to
severe bacterial conjunctivitis or keratitis (except Norfloxacin).
o Systemically can be used for UTI, GI, gonorrhea, sinusitis, respiratory and
skin structure infections, as well as burns.
Types
o 2nd Generation
 Norfloxacin (Chibroxin, Noroxin)
 Gram + and -; not pseudomonas.
 Topical 0.3% ophthalmic solution qid x7 days.
 Uses- Bacterial conjunctivitis, blepharoconjunctivitis, and
prophylaxis of conjunctivitis. Can be used only for the
treatment of conjunctivitis, but it is not indicated for
keratitis because less able to penetrate cornea than other
drugs.









Only for those greater than 1 year.
Least used, because it has been discontinued.
ADRs- Irritation, hyperemia, allergic reaction, lid margin
crusting
Ciprofloxacin (Ciloxan Solution, Cipro)
 This is the prototype. It is a broad spectrum antibiotic
effective against a variety of gram positive and gram
negative bacteria.
 It is more effective than aminoglycosides. Yet, many
strains of staph are resistant.
 Drug of choice for corneal ulcers 8x more effective than
other fluoroquinolones for treatment of pseudomonas
keratitis.
 Approved for bacterial conjunctivitis and keratitis.
 Also good against anthrax.
 Highest inhibitory quotient (IQ) = (Concentration in tissue
in mg/ml)/MIC = 90 in mg/ml.
 Dosage
o Available in topical ophthalmic solution 0.3%
(3mg/ml)
o Keratitis: 2gtt q1-2h in first 2 days, then 1 gtt q4h
x12days
o Ulcer: 2gtt q15min x6h, then 2gtt q30min x18h,
then 2gtt qidx24h.
o Conjunctivitis: 8-8x/day tapering to qid x5-7days.
 ADRs
o Irritation, hyperemia, burning sensation, FBS, white
precipitates due to the drug accumulating in the
epithelium.
Ofloxacin- topical 0.3% (Ocuflox, Ofloxin, Floxin)
 Broad spectrum activity against ocular pathogens.
 Highest level in aqueous of all fluoroquinolones (4x greater
concentration than others). Best corneal penetration.
 For corneal ulcers and moderate to severe conjunctivitis
and keratitis. FDA approved for ulcers. Also for bacterial
conjunctivitis, bacterial keratitis, and blepharitis. Indicated
for prophylactic antibiotic following refractive surgery.
 Dosage varies with severity
 ADRs
o Irritation, hyperemia, allergic reaction, lid margin
crusting, photophobia.
Lomefloxacin (Maxaquin)
Temafloxacin
Enoxacin
Nalidixic acid (NegGram)


o 3rd Generation
 Levofloxacin (Quixin, Levaquin)
 Approved for bacterial conjunctivitis and ulcers
 Good for G+/G-/H.flu/pseudomonas
 Day 1-2: q2h, 3-7: q4h
 ADRs- Mild ocular irritation
th
o 4 Generation
 Increased in vitro activity against G+, new pathogens, and resistant
G+ organisms
 Decreased pathogen resistance due to dual targeting of both DNA
gyrase and Topo IV.
 Gatifloxacin (Zymar, Tequin)
 G+, G Approved for bacterial conjunctivitis
 Contains PKA, a preservative
 0.3% solution, 2.5-5ml bottle
 1gt q2h while awake x 2 day, then qid
 Pregnancy C
 Only use in those greater than 1 year old
 Moxifloxacin (Vigamox, Avelox)
 G+, G Approved for bacterial conjunctivitis
 Best ocular penetration
 0.5% solution, 3ml bottle
 Preservative free
 1gt tid x 7 day
 Only use in those greater than 1year old
 Pregnancy category C
 Nitrofurantoin (Furadantin, Macrodantin)
 Possible mechanism- DNA damage
 Adverse effects include NVD and allergic reactions.
Side effects
o Although low, adverse reactions include burning after instillation, bitter
taste following instillation, superficial white precipitates in cornea (which
resolve after discontinuation of ciprofloxacin), itching, and foreign body
sensation. Opaque deposits on bandage SCL when Ciloxan is used
concurrently with prednisolone. White corneal precipitates have not been
reported in association with Ocuflox for ulcers 1-2gtt q30min.
o GI irritation and phototoxicity.
o Drug interactions- Aluminum, magnesium, iron and zinc salts interfere
with GI absorption. Effect on anticoagulants may be increased.
o NVD
o Cartilage damage in children
Contraindications
o Pregnancy, lactation, patients under 18 years.
o Avoid in patients with seizure disorders.
Inhibitors of transcription
Rifampin/ Rifampicin (Bacteria Streptomyces spp.)
 Not as common because resistance is fast
 Bactericidal
 Particularly effective against Mycobacterium tuberculosis, Neisseria meningitides
o Use in combination for treatment of M. tuberculosis, not used for
treatment of clinical infection of N. meningitides
 Mechanism of action
o Blocks initiation of RNA synthesis (transcription)
o Does not block synthesis that has already initiated (only new)
o Specific to bacterial RNA polymerases
 Mechanisms of resistance
o Chromosomal mutation of B-subunit of RNA polymerase. At least 5
polypeptides involved.
 Occurs at relatively high frequency (10-5)
 So use this with other antibiotics.
 Toxicity
o Rashes
Drug Affecting Intermediary Metabolism of Bacteria.
Sulfonamides

Mechanism of action
o Bacterial cells are impermeable to folic acid and must synthesize this
chemical internally from paraminobenzoic acid (PABA) to survive.
Sulfonamides compete for extracellular PABA to form nonfunctional
analogues of fake acid. This drug inhibits bacterial synthesis of folic acid
(pteroic acid) by preventing the step where PABA is converted to
dihydrofolate (dihydropteroate). Cells therefore cannot synthesize
thymidine, purines, and several amino acids.





o Sulfonamide-induced inhibition of folic acid synthesis can be reversed by
antagonistic compounds, such as PABA, local anesthetics (procaine,
tetracaine, benoxinate, and blood) because they are esters of PABA, pus,
and tissue breakdown products. Sulfonamide use is contraindicated for
infections with marked purulent exudation
Mechanisms of resistance
o Many forms have become resistant, therefore it is rarely used. Resistance
is due to either the overproduction of PABA by the bacteria, alteration of
dihydropteroate synthase, decreased enzyme affinity for the sulfonamide,
decreased bacterial permeability to the drug, or increased inactivation of
the drug by the bacteria. Widespread resistance has been encountered,
especially staph and pseudomonas.
Routes of administration
o Oral- All except sulfacetamide
o Topical- Sulfacetamide and silver sulfadiazine (good for burns)
o Available alone or in combination with a steroid.
Clinical Uses
o Otitis media in children, nocardiosis, and toxoplasmosis
o Useful spectra
 Bacteriostatic in low concentrations. Cidal in higher
concentrations.
 Broad Spectrum- Gram positive, gram negative, actinomyces,
Chlamydia, plasmodia, and toxoplasma
Dosing
o Tid-qid
o Ointment qhs.
4 groups
o Short acting (administered every 4-6 hours)
 Types
 Sulfisoxazole (Gantricin)
 Sulfamethizole
 Sulfacythine
 Sulfamethoxazole (Gantanol)
 Shortacting mixtures
o Trisulfapyrimidines
 Sulfamerazine
 Suldamethazine
 Sulfadiazine
 Newer sulfonamides are more soluble and are often
combined with older sulfonamides to reduce the chance of
UTI from the precipitation of acetylated drug crystals.
 Clinical indications
 Acute, uncomplicated 1st-episode UTI caused by E. coli
(drugs of choice- 1st sulfisoxazole, 2nd sulfamethizole,
sulfacytine, or sulfamethoxazole).


Chlamydial neonatal conjunctivitis (rare treatment choice.
1st systemic erythromycin)
 Adult inclusion conjunctivitis (1st/2nd tetracycline or
erythromycin. 3rd sulfonamides).
 Trachoma (1st tetracycline. 2nd erythromycin, 3rd oral
sulfamethoxazole and oral or topical sulfacetamide).
 Chlamydial venereal disease (1st/2nd tetracycline or
erythromycin. 3rd sulfonamide).
 Lymphogranuloma venereum and chancroid (1st/2nd
sulfonamide or tetracycline).
 Toxoplasmic retinochoroiditis (1st sulfadiazine and
trisulfapyrimidines).
o Long acting (administered once or twice daily)
 Not currently marketed in the US because of severe
hypersensitivity reactions (Steven-Johnson syndrome).
o Poorly absorbed
 Sulfasalzine
 Clinical indications- Prophylaxis before bowel surgery or
ulcerative colitis and regional enteritis.
o Topically absorbed.
 Sodium Sulfacetamide (Sulamyd, Bleph-10)
 10, 15, and 30% solutions, 10% ointment, in combination
with steroids prednisolone acetate and prednisolone
phosphate.
 Poor efficacy against staph, but still good for strep and H.
flu, therefore good to use with kids. Used for chronic
blepharitis.
 Ineffective for very purulent infections (PABA in pus).
 Sulfisoxazole- solution and ointment available.
 Silver Sulfadiazine
 Mafenide
 Bacterial conjunctivitis (strep pneumoniae and H. flu)
 Dosage: 10% sulfacetamide solution or 4% sulfisoxazole
solution. Instill 1 drop every 2 hours for severe infections
or 1 drop tid-qid for chronic conditions. Ointment form
usually reserved for bedtime or for children.
 General uses
 Alternative to erythromycin for chlamydial neonatal
conjunctivitis.
 Alternative to tetracycline or erythromycin for adult
inclusion conjunctivitis.
Adverse effects
o From systemic therapy
 Gastrointestinal irritation, anorexia, N, V, diarrhea
 Blood dyscrasias (rare)- Acute hemolytic anemia, aplastic anemia,
agranulocytosis, thrombocytopenia, and leukopenia.


Toxic levels of free bilirubin in infants. Sulfonamides cross the
placenta easily and compete with bilirubin for albumin binding.
Sulfonamides not advisable for lactating mothers and pregnant
women close to term.
 Hypersensitivity reactions (systemic or topical route)- Urticaria
and rashes (accompanied by pruritis and fever), malaise, serum
sickness-like syndrome, joint pain, immune corneal ring formation
(topical administration), erythema multiforme (Steven-Johnson
syndrome), and exfoliative dermatitis. If a patient is allergic to one,
they are allergic to all.
 Transient myopia (with/without induced astigmatism)
 Local photosensitization (with sulfonamide ointment)- sunburns
 Multiple small white concretions of sulfadiazine within cysts in the
palpebral conjunctiva (with topical sulfadiazine ointment).
 White plaque formation on the cornea (with topical sulfadiazine
ointment).
 Decrease in corneal sensitivity (with 30% topical sulfacetamide)
 Bone marrow depression
o Adverse drug interactions with
 Hypoglycemic drugs (tolbutamide and chlorpropamide)
 Coumarin anti-coagulants
 PABA-containing compounds and PABA analogs (procaine).
Contraindications
o Pregnant or nursing women due to the fact that it causes an increased
production of bilirubin and decreased blood sugar leading to
hypoglycemia.
o Age less than 2 months
o Blood dyscrasias
o Oral hypoglycemic drugs
o Coumarin anticoagulants.
o PABA esters (e.g. local anesthetics)
Antimetabolites
 Many different types.
 Interfere with metabolic processes specific to bacteria or that use enzymes or
other macromolecules different between bacteria and humans.
Sulfonamides
 First widely used antibacterial agents in 1930s. this started the chemotherapy age.
 Mechanism of action
o Sulfonamides are structural and functional analogs of para-aminobenzoic
acid (PABA)
 Act as competitive inhibitors of reaction during biosynthetic
pathway to folic acid
 Most bacteria must synthesize their own folic acid; humans take in
folic acid in diet.



Mechanism of resistance
o Active efflux of antibiotic (plasmid-mediated)
o Chromosomal mutation altering dihydropteroate synthase (target enzyme)
Toxicity
o Fairly low
o Bone marrow depression
o GI distress
o Fever, HA, depression
o Hepatic necrosis
o Allergic reaction
Uses
o Useful as hypoglycemics, diuretics, and antihypertensives
Trimethoprim
 Antagonist of dihydrofolic acid in bacteria (used to synthesize folic acid in
bacteria)
 Acts synergistically with sulfonamides since they inhibt 2 different steps in
biosynthesis of flic acid (often prescribed together)
 Mechanism of action
o Blocks synthesis of tetrahydrofolic acid by inhibiting dihydrofolate
reductase
o Bacterial enzymes are 20,000-60,000 times more sensitive than
mammalian cells.
 Mechanism of resistance
o Bypass metabolic block by using alternative substrates present in
environment (use of exogenous materials)
o Altered enzyme
 Toxicity
o Same as sulfonamides
o Bone marrow depression
o GI distress
o Fever. HA, depression
o Hepatic necrosis
Isoniazid
 Bactericidal
 Widespread and dramatically successful use against tb in 1950s.
 Mechanism of action
o Inhibits synthesis of mycolic acid (cell wall component of Mycobacterium
but no other organism)- so only kills Mycobacteria
 Mechanisms of resistance
o Reduced uptake of antibiotic
o M. tuberculosis has high rate of mutation to resistance (10-6)
o Used in combination with other antimycobacterial antibiotics.
New Antibiotics






Synereid- approved 9/99
o 2 semisynthetic streptogramin Abs (quinupristin and dalfopristin)
o Inhibits protein synthesis by binding ribosomes
 Similar to macrolides without cross reactivity
o Primarily for treatment of VRE and staph, strep, and neisseria
o Problem with toxicity
Zyvox- 4/00
o Developed and approved specifically for staph infections
o Also for VRE
o From fully synthetic class of Ab
o Inhibits protein synthesis but by different mechanisms from other protein
synthesis inhibitors.
New promising Ab candidates isolated from lactococcus lactis
o Peptide (nisin) has been used as a food preservative (dairy and other
products)
o Acts at same site as vancomycin but may have a different mode of action.
o No resistant organisms have yet been found (but not used yet)
Ramoplanin produced via fermentation of Actinoplanes species
o Inhibits cell wall peptidoglycan biosynthesis
o Actively seen against G+ aerobic and anaerobic microbes, (VRE and
methicillin-res staph)
Nanobiotics
o Disrupt bacterial membranes via implantation and holes to increase
permeability and death.
o No resistance. Just simply peptides inserting themselves.
Bacteriophages as a possible Ab.
o Difficult to isolate and mutate rapidly.
Summary
Viruses
Introduction
 Viruses are nonliving organisms. These are only visible with an electron
microscope. Although they are not visible to the naked eye, they can cause visible
changes, such as occlusion bodies.
 They have a simple, acellular organization, meaning that they contain no
organelles. They also contain one type of nucleic acid, either DNA or RNA, but
never both.
 These are obligate intracellular pathogens incapable of undergoing normal cell
division. The virus depends on the host for metabolic machinery and
reproduction. It can survive outside the host for short periods of time only. In the
host, the viruses can cause a host of problems, including acute illness (i.e. flu),
chronic illness (i.e. hepatitis), or inactive problems (i.e. chicken pox).
 Exist in one of two states
o Extracellular
 Effectively a package on its way to infect the next host
o Intracellular
 Usurping host machinery to make multiple virions
 Replication of viral genome, transcription, translation of viral
genes
 Classification
o Type of nucleic acid (DNA/RNA)- by molecular weight and structure
 Have either DNA or RNA in virion (complete virus particle)
 Type of nucleic acid is used in classification
 Small amount of nucleic acid relative to cells
o Therefore, limited coding capacity for genes
o Single-stranded or double-stranded
o Envelopes: presence or absence
o Shape of protein coat or capsid.
o All viruses are haploid with exception of retroviruses which contain two
identical copies of its genome.
o Also, molecular weight, arrangement of genome, shape, and biological
characteristics of the virus.
 Viral assays
o Hemagglutination assay
 Many viruses can bind to the surface of RBCs
 Especially true of animal viruses
 If ratio of viruses to blood cells is high enough, each virus can
interlink several red blood cells forming a network which settles
out (agglutinates)
 Can determine titer of virus preparation based on dilution at which
hemagglutination occurs.
 Concentration is the lowest concentration of agglutination
o Plaque Assay








Infect appropriate host cells with virus preparation
Overlay with agar to prevent over-spreading of virions
Plaques are localized areas of cell lysis/damage (can be viewed
with microscopes)
If virions were dilute enouth, each plaque would correspond to one
original virion
 Plaque forming units (PFU)
CPE- Cytopathic Effect- damage to cells that you are looking for
in an assay
Also look for viral specific antigens (proteins) and inclusion bodies
See atypical shapes in leukocytes
Syncyti formed sometimes (cell fusion), causing a “mege cell”
Viral Structure
 Size
o Highly variable- 10-400nm in diameter. This corresponds roughly to the
spectrum of sizes from that of the largest protein to that of the smallest
cell.
o Their shapes are frequently referred to in colloquial terms, e.g., spheres,
rods, bullets, or bricks, but in reality they are complex structures made up
of repeating subunits of precise geometric symmetry.


The virion consists of a protein coat (capsid) made up of capsomeres, nucleic acid
(ssDNA, ssRNA, dsDNA, or dsRNA) and an outer envelope if it has one.
The viral nucleic acid (genome) is located internally and can be single or double
strands of RNA or DNA surrounded by a capsid (protective protein coat), and
sometimes an envelope. The nucleic acid can be either linear or cicular. The DNA
is always a single molecule. The RNA can exist as a single molecule or in
fragments.
o Viral proteins serve several important functions. The outer capsid protein
coat protects the genetic material and mediates the attachment of the virus


to specific receptors on the host cell surface. Some of the internal proteins
are associated in the replication process.
Coatings
o Capsid
 This is made up of subunits called capsomeres. The arrangement of
capsomeres gives the viral structure its geometric shape.
o Envelope
 Some viruses are composed of an external lipoprotein membrane
(envelope) derived from the host cell membrane. Glycoproteins in
the form of spikelike projections on the viral surface attach to host
cell receptors during the entry of the virus into the cell.
General Structure
o All virions have nucleocapsid composed of nucleic acid held within
protein coat called capsid (protective. Still variation)
o Four types of structures
 Icosahedral- Naked (no membrane)
 Regular polyhedron with 20 equilateral triangular faces and
12 verticies
 Constructed of capsomers [consisting of 5-(pentamers,
pentons) or 6-sided (hexamers, hexons) protomers]
o Other combinations of 5 and 6 are also seen.
 Prototypical
 Helical- Simplest
 Hollow protein cylinders surrounding the nucleic acid
 Usually single type of protein (protomer)
 Enveloped
 Outer membranous layer
 Usually spherical in shape
 Viral envelopes

o Envelopes arise from host cell membranes as it
exits, but not proteins
o Proteins present are encoded by viral genes that are
specific
 Often look like spikes
 Important for attachment and entry of virus
into the host cell
 i.e. influenza virus
 Complex Viruses
 Symmetry is neither completely icosahedral nor helical
 Often have tails or complex wall structures
 Both icosahedral and helical capsids are macromolecules
made of many copies of one or few proteins subunits called
protomers
 Because simplest requirements for genes for protomers,
have rest of genome for other genes.
 Some genes may overlap to minimize the number of genes
to make a capsid.
Nucleic Acids (also varies)
o Single or double-stranded DNA or RNA

o Linear or circular or linear with the ability to become circular (due to
cohesive overlapping ends that are complementary)
o Wide range of sizes from 3 kb (max 3-4 proteins) to 240 kb (max>100
proteins)
o Most RNA viruses have single stranded RNA
 May match viral mRNA, therefore plus or positive strand
 Translation of viral genes can begin immediately
 If complementary to viral mRNA, therefore minus or negative
strand
 Positive strand RNA must be produced before translation
can occur
 Often segmented genomes
 i.e. influenza
 Different genetic pieces fit together
 Consequences
 Plays a role in great flu epidemics, because if multiple
influenze viruses are present, the pieces can be shuffled to
create something the immune system is not ready for.
 CDC tracks different viruses, and the vaccinations become
a “guessing game.”
 8-20 viruses are present at one time. So they guess which is
most likely to appear. This means that sometimes it does
not work.
Genes
o Overlap
o No excess, therefore need to squeeze as many genes as they can into what
they have.
o The smallest bacteria has about 450 genes, the largest virus has about 100.
Viral Genetics
 Mutations and their effects on replication and pathogenesis
o Mutations occur by base substitutions, deletions, and frame shifts as those
described in biochemistry. The most important practical use of mutations
is in the production of vaccines containing live, attenuated virus.
Attenuated mutants have lost their pathogenicity but have retained their
antigenicity to induce immunity.
 Adsorption and Penetration
o Adsorption- tail fibers attach to host cell membrane.
o Penetration- virus enters host cell.
o Encounter between virus and susceptible host cell is random event
o Attachment is specific event requiring appropriate receptors on cell
 Not simply there for virus
 All have other functions
 Viruses simply utilize them as attachment/entry sites
o May involve coat proteins or special viral proteins for attachment

o They inject their genertic material into a host cell and replicate by lysis or
lysogeny. Lysis causes the cell to rupture as new virus particles are
released. Lysogeny preserves the host cell by having new virus particles
bud off from the cell membrane.
Penetration and uncoating
o Some non-enveloped viruses may simply inject DNA


This is like a hypodermic. It is the simplest form.
See multiplicity of infection.
 50-200 bacteriophages




o The envelopes of some enveloped viruses may fuse with cellular plasma
membrane allowing entry of the nucleocapsid. It sort of “dissolves” in.
o Most enveloped viruses probably enter through endocytosis.
o Envelope is either shed upon entry or after endocytosis.
 Leads to release of nucleocapsid by ribosomes
 Uncoating usually occurs in cytoplasm
 If viral proteins also found in virion, these are not released as well.
Preparation for assembly of virions
o Host DNA, RNA, protein synthesis halted due to actions of viral gene
products
 Sometimes host macromolecules are degraded, or kept going to get
more material, etc.
 Degradation products (nucleotides, amino acids) used to replicate
nucleic acids, synthesize viral proteins
o Early viral genes involved in taking over host cell machinery and making
early viral gene products
 Temporal control when viral genes take over.
o Modification of host RNA polymerase to only recognize viral promoters.
 Genes with related functions often clustered on viral genome.
Viral replication in host cells
o The infecting parental virus particle attaches to the cell membrane and
then penetrates the host cell. The viral genome is “uncoated” by removing
the capsid proteins and the genome is free to function. Early mRNA and
proteins are synthesized (gene expression). The early proteins are enzymes
used to replicate the viral genome. Late mRNA and proteins are then
synthesized. These late proteins are the structural, capsid proteins. the
prgeny virions are assembled from the replicated genetic material and the
newly made capsid proteins and are then released from the cell.
o The lysogenic cycle occurs when the viral DNA becomes integrated into
the host cell chromosome and no progeny virus particles are produced.
Because the integrated viral DNA is replicated along with the cell DNA,
each daughter cell inherits a copy. It can be induced to resume its
replicative cycle by the action of UV light and certain chemicals that
damage DNA. Enzymes are produced that excise the prophage (viral)
from the cell DNA. The virus then completes its replicative cycle.
Replication and transcription in DNA viruses
o Early viral gene products designed to turn off host cell machinery
o Usually do not degrade host DNA (they just chop it up)
 May be conflict with degradation of viral DNA
o Most replication occurs in nucleus
o Simple viruses use only host machinery
o More complex viruses may bring in or code for viral RNA polymerase,
DNA polymerase, etc.
Replication and transcription in RNA Viruses
o Many variations- depending on RNA strand (+ or -)
o General schemes
 Picornaviruses (poliovirus)
 +RNA
 Genome acts as large mRNA for translation
 Viral replicase to make dsRNA (RF = replicative form)
o ds = double strand
 +RNA produced to package into virion
 Reoviruses, such as rotavirus responsible for infant diarrhea
 +/- RNA
 Virus associated transcriptase copies negative strand RNA
to produce mRNA
 Virus-encoded polymerase continues transcription to
replicate genome.
 Negative singe-stranded RNA viruses (paramyxoviruses- mumps
and measles, orthomyxoviruses- influenza)
 -RNA
 RNA-dependent RNA polymerase to make mRNA
 Viral replicase to make dsRNA (RF)
 Retroviruses (Rous sarcoma virus, HIV)
 +RNA





RNA-dependent DNA polymerase (reverse transcriptase) to
make –DNA copy (“backwards”)
 Ribonuclease H component of reverse transcriptase
degrades RNA, leaving the –RNA
 Reverse transcriptase makes dsDNA called proviral DNA
o Proviral DNA integrates into host genome
 Transcription of dsDNA gives mRNA and full-length
+RNA for virions
Assembly of viral particles
o Synthesis and assembly of virus capsids
 Capsid proteins can self-assemble to form procapsid
 Nucleic acid then inserted
 Assembly occurs spontaneously when appropriate nucleic acids
and coat proteins are present.
Virion release
o Naked virions released upon cell lysis
 Specific genes involved in lysis of host
o Enveloped viruses different
 Viral proteins incorporated into host plasma membrane
 Nucleocapsid assembly occurs in cytoplasm
 Virion exit and envelope formed by budding from cell.
 This is the opposite of fusion.
Terms
o Biosynthesis- viral DNA/RNA replicated in host cell.
o Maturation- DNA/RNA and capsids are assembled.
o Release of particles by budding or by rupture of cell membrane.
o Recombination- the exchange of genes between two chromosomes that is
based on crossing over within regions of significant base sequence
homology. Recombination occurs between the genomes of two similar
DNA viruses and less readily between RNA viruses (e.g., pox virus).
o Reassortment- a specialized form of recombination that takes place
between viruses with segmented genomes, such as influenza virus and
involves the exchange of segments. This can result in major antigenic
changes (e.g., antigenic shift for influenza) resulting in major epidemics.
o Complementation- occurs when one of the two viruses that infects the cell
has a mutation that results in a nonfunctional protein. The nonmutated
virus complements the mutated one by making a functional protein that
serves for both viruses.
o Phenotypic mixing- when the surface proteins of one virus appear on the
surface of another virus allowing that virus to enter (and usually infect)
cells in the host.
Persistent, latent infections
o In persistent or chronic infections, virus reproduces at very slow rate
without causing disease symptoms
 Antibodies against virus seen/produced. This prevents active
replication.



o In latent infection, virus reproduction halted
 Remains dormant, possibly for years.
 No symptoms or antibodies seen.
o Various factors or conditions can trigger reactivation of virus.
 Herpes simplex virus type I causes cold sores
 Varicella-zoster virus initially causes chickenpox but later
shingles.
 Nasal spray immunization more effective than shot
o Flumist from Aviron
Importance
o Influenza virus
 US- 35-50 million cases/year; 20,000 deaths
 Severe epidemic, based on estimates including 172,000
hospitalizations, would cost at least $12 billion in medical
expenses and lost productivity.
Defective Virus Particles (due to no repair mechanism)
o Often present within a population of infecting virions or can evolve
through mutation, deletion, etc.
o May play a role in self-limiting infections
o Also a role in establishment and maintenance of persistent infections.
Principles of Viral Disease
o Many subclinical
o Some apparent disease caused by a variety of viruses
o Some virus may cuase a variety of diseases
o Outcome in an individual case is determined by genetic makeup of the
virus and host.
o Site of infection
o Food-borne Viral Illness
 About 9.2 million cases due to Norwalk-like virus
 Present in shellfish harvest in waste polluted water
 Transmission to food via unwashed hands
o The ability of viruses to cause disease can be viewed on two distinct levels
 The changes that occur within individual cells
 The process that takes place in the infected individual.
o The 4 main effects of virus infection on the cell.
 Death of the cell when cellular proteins are not synthesized and
only viral protein synthesis occurs. Infected cells frequently
contain inclusion bodies, which are discrete areas containing viral
proteins or viral particles. Electron micrographic analysis of
inclusion bodies can aid in the diagnosis when viral particles of
typical morphology are visualized.
 Fusion of cells to form multinucleated cells occur as a result of cell
membrane changes with the insertion of viral proteins into the
membrane. Multinucleated giant cells characteristically form after
infection with herpes virus and paramyxovirus and therefore the
presence of eosinophilic intranuclear inclusions is diagnostic for
herpesvirus skin infection.
 Malignant transformation is characterized by unrestrained growth,
prolonged survival, and morphological changes such as focal areas
of rounded, piled-up cells.
 No apparent morphologic or functional change.
o Pathogenesis in the infected patient involves:
 Transmission of the virus and its entry into the host. Viruses can be
transmitted from person-to-person, e.g., respiratory secretions,
saliva, blood, semen, and fecal contamination of food or water. Or
between mother and offspring in utero across the placenta, at the
time of delivery, or during breast feeding. Animal to human
transmission can take place via a bite of the vector or the reservoir.
Or a latent, nonreplicating virus can be activated to form an active
replicated virus within the individual.
 Replication of the virus and damage to cells.
 Spread of the virus to other cells and organs: viral infections are
either localized to the portal of enrty or spreads systemically
though the body. The best example of the localized infection is the
common cold localized to the upper repiratory tract. In contrast,
poliomyelitis is a systemic viral infection that infects the cells of
the small intestines after the poliovirus is ingested. It spreads to the
mesenteric lymph nodes where it multiplies again. It then enters
the bloodstream and is transmitted to the CNS, where damage to
the cells of the anterior horn occur, resulting in the characteristic
muscle paralysis. It is during this obligatory viremia that
circulating IgG antibodies induced by the polio vaccine can
prevent the virus from infecting the CNS.
 The immune response, both as a host defense and as a contributing
cause of certain diseases. The signs and symptoms of most viral
diseases undoubtedly are the result of cell killing by virus-induced
inhibition of macromolecular synthesis. However, there are certain
diseases in which the death of the cell is caused by immune attack
by cytotoxic T cells on the new viral antigens in the cell membrane
rather than by virus-induced inhibition of cell functions.
 Persistence of the virus in some instances by the
 Mechanisms include
o Integration of a DNA provirus into host cell DNA,
as with retroviruses
o Immune tolerance, because neutralizing antibodies
are not formed.
o Formation of virus-antibody complexes, which
remain infectious.
o Location within an immunologically sheltered
sanctuary, e.g., the brain.
o Rapid antigen variation


o Intracellular spread so that virus is not exposed to
antibody.
o Immunosuppression as in AIDS
Three types of clinically important
o Chronic-carrier infections, i.e., hepatitis B
o Latent infections, e.g., varicella-zoster
o Slow virus infections, e.g., subacute sclerosing
panencephalitis following measles.
New Viruses
o Arenavirus kills a girl in 2000 transmitted by a rat.
o Enterovirus reported in Newport in 2000
How Infectious Agents Cause Disease
 Viral infections change host cells (can be identified with a disease)
o Enlargement of cells
o Eosinophilic inclusions
o Multinucleated cells
o Nuclear and cytoplasmic inclusions
 Viral infections may affect host cells by:
o Inducing replication
o Necrosis
o Viral latency
Diagnosis of viral diseases by the use of clinical specimens
 Identification of the virus in cell culture: viral growth in cell culture frequently
produces a characteristic cytopathic effect (CPE) that can provide a preliminary
diagnosis. Other techniques include: complement fixation, hemagluttination
inhibition, neutralization, fluorescent antibody, radioimmunoassay, ELISA, and
immunoelectron microscopy.
 Microscopic identification directly in the specimen: identification of inclusion
bodies. With fluorescent antibody. Or via electron microscopy.
 Serologic procedure to detect a rise in antibody titer or the presence of IgM
antibody.
Viral Pathology
The Common Cold
 Respiratory Viruses
o Rhinovirus and Coronavirus- URI (vs. LRI- bronchitis, etc)
 Most common viruses with “colds”
 Usually a mild disease not associated with pneumonia
 Clinical symptoms are limited to rhinorrhea, pharyngitis, cough,
and low grade fever
 Complications may include sinusitis and otitis media.
 These respond poorest to antibiotics



Cold Vs. Flu
o Cold
 Runny nose, sneezing
 Sore throat
 Localized
o Flu
 Runny nose, sneezing
 Sore throat
 HA
 Muscle aches
 Fatigue
 Higher fever (103)
 Systemic
 More severe
Influenza A/B Infections
o Cause of major epidemics throughout history
o Viral isolates can change annually due to antigenic drift or antigenic shift.
 These shifts can be predictable, allowing immunizations to be
changed.
 Birds and pigs may contribute to these antigenic changes
o Clinical Features
 Rapid onset of fever, chills, myalgia, and cough.
 No nausea, vomiting, or diarrhea
o Pathology
 Causes necrosis and desquamation of the ciliated epithelium and
induces inflammatory response.
Adenovirus
o Numerous types of adenoviruses are associated with human infections
from respiratory infections, eye, GI, and UTIs.
o Polyhedral, no envelope, naked dsDNA, 40 types, associated with
infections of respiratory tract or eye.
o Clinical syndromes
 Causes a cold-like syndrome
 PCF
 Pertussis-like illness
 Rapidly fatal hemorrhagic pneumonia in immunocompromised
hosts.
o Fecal or water-borne
o Vaccination is available to certain populations
o Dz
 Common cold
 Acute undifferentiated non-streptococcal pharyngitis. Sore throat,
fever, lymphadenopathy, follicular conjunctivitis often present.
 EKC
o Diagnosis
 Can be cultured in standard culture




Pathology
 Causes areas of extensive necrosis, hemorrhage, and
inflammatory infiltration.
Parainfluenza infections
o Four types designated 1, 2, 3, and 4.
o Causes mild croup, cough in adults.
o Causes acute pneumonitis with a barking cough in children, as well as
striter (noise made with inhalation)
o No vaccine currently available
o Diagnosis
 Can be cultured in routine laboratory
 Pathology
 Virus infects and kills ciliated respiratory epithelial cells leading to
an inflammatory response.
Croup
o Signs
 Anterior and posterior X-rays show the classic steeple sign with
narrowing of the tracheal air column at the larynx and distension of
the hypopharynx.
 Also in the epiglottis, look for a thumb sign with lateral xrays. This
is seen more in older kids.
o Treatment
 Humidification- examples include vaporizer, steam bath, or night
air.
 Adequate hydration
 Racemic epinephrine nebulization shrinks the tissue
 Oxygen if indicated
 Consider corticosteroids
 Endotracheal intubation if indicated
Respiratory Syncytial Virus (RSV)
o Transmitted by close contact and epidemics occur in the winter months.
o Causes mild infection in adults, because our airways are larger.
o Causes acute lower respiratory disease in children (pneumonia and
bronchiolitis)
o No vaccine currently available
o Ribovarin is used in severe disease
o Diagnosis
 Can be cultured in routine virology laboratory
 Direct detection of antigen by enzyme immunoassay or
immunofluorescence
 Pathology
 Viral infection causes fusion of infected cells (syncycia)
leading to multinucleated giant cells.
Viral Exanthems
 Measles (Rubeola)

o Highly contagious, spread by direct contact or fomites (nose, mouth,
throat)
o Incubation period is about 10 days
o Clinical symptoms are fever, cough, coryzam conjunctivitis, and a rash on
the 4th or 5th day.
o Blotchy purplish rash in a child with a runny nose and sore eyes. The rash
starts on the face or head and then spreads to the trunk and extremeties.
The rash will also involve the palms and soles. If seen on adults, think
syphilis.
o Koplik spots often are noted on the buccal or labia mucosa (minute bluishwhite lesions with a red halo)
o Warthin-Finkeldey multinucleated giant cells are distinctive for measles
o Measles vaccination is part of the MMR given to children at 15 months of
age.
o Very rare now
o Complications of measles
 Infection of the lower respiratory tract (giant cell pneumonia)
 Otitis media
 Postinfectious encephalitis
 Subacute sclerosing panencephalitis (SSPE) can be a late
complication occurring 4-17 years after recovering from measles.
o Vaccination
 Total cases in 1960
399,852
 Vaccine was introduced in 1968
 Total cases in 1970
39,365
 Total cases in 1982
1,188
 Total cases in 1986
6,282
 Total cases in 1989
16,236
 This spike was due to no immunization
 Total cases in 1999
100
Rubella (German Measles)
o Highly contagious
o Humans are the only host
o Incubation period is 10-21 days
o Clinical manifestations are mild
 Low grade fever
 Lymphadenopathy
 Maculopapular rash
 ½ flat, ½ raised
 typical diffuse, pink, macular rash over the face and trunk. The
rash usually resolves after 3-4 days.
o Pathology
 Variable including desemination to all organs
 Young children can secrete large quantities of virus in body
secretions for many months
 Diagnosis is usually made by serology


o Vaccination- part of MMR shot, but it wears off.
o Congenital Rubella Syndrome (CRS)
 Fetal infections during the first trimester are the most damaging.
 This is much worse than if you get it later in life.
 Infection can cause deafness, glaucoma, CHD, mental retardation
or death.
 1964 there were >20,000 cases of CRS
 1983 there were only 3 cases reported
 between 1997 and 1998, there were 0 cases.
 In 1999 there were 36 cases (all in Kansas)
Mumps
o Highly contagious (direct contact or fomite)
o Clinical symptoms
 Usually associated with an uncomplicated infection of the salivary
glands (parotiditis). See swelling, and huge cheeks.
 Bilateral parotid and submandibular gland enlargement.
 In males, can see orchitis (inflammation of the testes) and
infertility.
o Part of the MMR vaccine
 In 1967 there were 185,691 cases of mumps
 In 1982 there were 5, 270
 In 1999 there were 338.
o No antiviral drugs are currently available.
o Diagnosis
 Virus can be cultured by standard methods
 Diagnosis is usually made by serology
Parvovirus B19
o Only parvovirus that is pathogenic in humans.
o Causes the childhood disease known as erythema infectiosum (fifth
disease)
o Spread via respiratory secretions
o Clinical manifestations are
 Bright red cheeks, called “slapped cheeks”
 The rash on the extremeties clears centrally to produce a lace-like
appearance.
 Exanthema is lacy or reticular and may be macular or
maculopapular
 Other symptoms are mild in normal children (low grade fever, sore
throat, cough).
 Older patients manifest symptoms as joint pain and fevers. There is
no rash.
o Parvovirus B19 infects erythroid precurose cells that leads to transient
anemia.
o Certain populations are at high risk for morbidity and mortality when
infected with parvovirus 19.


Patients with sickle cell disease, thalessemia, or chronic anemia
can have aplastic crisis that is very severe.
 Can cause hydrops and fetal death after maternal infection.
 Immunodeficient patients can have disseminated disease and suffer
chronic anemia that requires transfusions.
 Those that are pregnant.
Smallpox (Variola)
o Smallpox was a severe generalized disease. Smallpox was eliminated in
the world due to widespread vaccination. The WHO determined that the
world was free of endemic smallpox in 1979.
o Immunization against smallpox was discontinued in the 1980s and there is
a growing percentage of the world’s population that not lacks immunity to
this deadly disease. It is currently on the bioterrorism agent list for
possible use as a weapon against humans.
Gastrointestinal Virus
 Rotavirus
o Can cause asymptomatic to severe, fatal disease
o Watery diarrhea with no blood or leukocytes, associated with fever and
vomiting
o More severe in young children. Gastroentitis can lead to death with severe
nausea and vomiting.
o Pathology
 Primarily affect the small intestine
 Virus replicates in epithelial cells
 Large amounts of rotavirus are excreted in the stool
 Detected by electron mincroscopy
 Detected by enzyme assay to detect antigen.
 Caliciviruses and Norwalk/Norwalk-like viruses
o Virus particle is small (30-35nm) and round.
o Mild symptoms that last 24-72 hours
o Watery diarrhea, abdominal cramps, and vomiting
o About 50% of individuals exposed to the viruses will have symptoms
o All individuals will secrete virus
o Immunity is short-lived.
o Diagnosis is usually clinical.
o Outbreaks have been studied using molecular diagnostic methods and
typing.
o Highly contagious
o Treatment- do not slow bowel movements. Just replace liquids.
 Adenoviris 40 and 41
o Associated with infantile diarrhea
o These isolates cannot be isolated in the laboratory.
o Symptoms range from mild diarrhea to severe profound dehydration.
o Incubation is 3-10 days and diarrhea can last from 6-9 days
o Diagnosis is usually clinical and treatment is supportive.
o Decreased severity than rotavirus
o No specific treatment
Viruses Associated with Epithelial Growth
 Warts due to viruses
 Molluscum contagiosum
 Human poxvirus
 Causes a benign wart-like lesion transmitted by direct contact
 Can also be spread by scratching.
 Disease is self-limiting but may last from months to years.
 Lesion is an umbilicated papule that is flesh-colored with a central depression
 Pathology
o Molluscum body which is seen in the center of the lesion.
Human Papillomavirus
 Causes epithelial neoplasms of skin and mucosa
 Associated with
o Common wart (verruca vulgaris)
o Plantar wart (on feet or hands)
o Anogenital warts (condyloma acuminatum)
 There are over 60 different types and different viral types are associated with
different lesions
 HPV infection produces squamous proliferation lesions.
 Pathology of infected cells is a characteristic cytopathic effect termed
kollocytosis.
 This can cause all warts except molluscum contagiosum
Human Herpesviruses
 Characteristics
o Polyhedral, enveloped, dsDNA, persistence of virus in body, usually in
latent form, show reactivation.
o Enveloped DNA viruses
o Ubiquitous and ancient virus
o Establish a latent infection
o Can cause a clinical or subclinical reactivation
o They can especially cause severe disease in neonates and
immunocompromised patients
o Pathologically many of them produce a Cowdry type A nuclear inclusions
(acidophilic body surrounded by a halo).
o Treatment with antiviral meds.
o It is possible to have no symptoms and still be contagious.
 Types
o Herpes Simplex I and II (HSV)
 HSV I and II establish a life-long infection
 The virus alternated between a latent and an active infection.

HSV commonly causes oral facial infections (cold sores, herpes
labialis) and/or genital lesions.
 Virus is shed from the vesicles within the first 24 -48 hours after
the onset of symptoms
 Once crusting, they are not contagious.
 Primary or recurrent infections in immunocompromised patients
may be severe and prolonged.
 Primary infections
 Ulcerative lesions of the gums, tongue, and palate or the
tonsils and pharynx.
 Associated with fever, malaise, diarrhea, and cervical
lymphadenopathy.
 Recurrent Infections
 Preceded by burning, itching, or pain
 Progresses through erythema, vesicles, ulcers, and crust.
 Also see ulcers, lesions, fatigue, and lymph node swelling.
 Triggered by stress
 HSV I- oral lesions
 HSV II- genital herpes
 HSV also causes the following diseases
 Herpes keratitis- can cause blindness due to corneal
scarring
 Herpetic Whitlow
o On hand, common with dentists
 Herpes encephalitis
o 70% mortality with untreated
o Most commonly caused by HSV I
o Difficult to culture. Must use PCR
 Neonatal Infection
o Infected via birth canal.
o Varicella Zoster Virus (VZV)
 Chicken Pox
 A lifelong infection with the virus residing in the sensory
ganglia.
 Reactivation of VZV causes Zoster
 Incubation of 10-20 days
 Spread via direct contact
 Clinical manifestations- fever, chills, myalgias, followed by
the development of vesicular lesions.
o Early rash with macules, papules, and superficial
vesicles.
o “Dew on a rose petal”
 macule vesicles with fluid.
 Skin proken with ulceration and bacteria
gets in.

Painful with adults (increased rate of
encephalitis/pneumonia)
o All lesions are not the same.
o With chickenpox, you are at risk for shingles
(localized, unilaterally) and post-herpetic neuralgia.
 Complications
o Bacterial superinfection of lesions
o Mengioencephalitis
o Pneumonia
o Hepatitis
 An effective vaccine was licensed in the US in 1995
(Varivax). Immunization now common.
 Herpes Zoster (Shingles) is the consequence of reactivation of
latent VZV.
 Occupies the sensory ganglia
 Characterized by unilateral vesicular rash and accompanied
by excruciating pain. The vesicles are of varying size with
an erythematous base.
 Virus is localized within the dermatome of the vesicular
eruption.
 Virus can be isolated from the lesions and a Tzank smear
will show multinucleated giant cells.
 50% of patients will experience persistent severe pain for
up to 6 months after resolution of lesions (postherpetic
neuralgia)
 In immunocompromised patients zoster may become severe,
chronic, or recurring.
 Zoster is contagious to individuals who have never had chicken
pox.
o Cytomegalovirus (CMV)
 Type V herpes
 “Big Swollen Cells”
 this can be very common, especially with decreased immune
system. Most cases clinically inapparent: widespread.
 CMV is transmitted by close contact
 Virus is shed in urine, saliva, semen, breast milk, and
cervical secretions.
 CMV is found in lymphocytes and monocytes
 Seroprevalence worldwide ranges from 30-100%
 Clinical infection
 Congenital infections, mononucleosis, hepatitis
 Immunocompromised patients can have disseminated
disease.
 Mono-like symptoms
o Fatigue, sore throat, hepatitis, and fever.
 Three clinical types
 Perinatal diseases (congenital infection)
 Acute acquired (like infectious mono)
 Infection in immunosuppressed patients.
 Antiviral drug gancyclovir is used for active CMV infections.
 Diagnosis
 Culture- both standard and rapid
 Serology- IgM
 Pathology- cytoplasmic and nuclear enlargement with
nuclear inclusions.
o Liver biopsy- enlarged cytoplasm with nuclear
inclusions and clearing around the nucleus = “Owleyed cells”
o Same is seen in kidney biopsy.
Syndrome
Useful Test
CMV Mononucleosis
CBC with peripheral blood smear
CMV IgM Serology
CMV culture of blood
Congenital and Neonatal CMV Infection
Culture of urine
Biopsy of liver, kidney, or spleen
o Epstein-Barr Virus (EBV)
 In most cases the infection is asymptomatic in children.
 Can be acute (infectious mononucleosis) or chronic.
 Older children and adults are more likely to develop symptoms of
mononucleosis after a primary infection
 Characterized by fever, sore throat, lymphadenopathy, and
heptosplenomegaly.
 Cervical lymphadenitis with no visible sign of acute
inflammation
 Gross tonsilar enlargement with a white exudates
 Increase in circulating lymphocytes and atypical
lymphocytes in the blood.
 Induces a polyclonal activation of B cells (detected as
heterophil antibodies)
 Mono with Amoxicillin
o If react with a rash, it is mono.
 Diagnosis
 Detection of heterophil antibodies (Monospot)
 Detection of EBV specific antibody.
 EBV is also associated with
 African Burkitt’s lymphoma
 Nasopharyngeal carcinoma
 Lymphoproliferative disorders in transplant patients
 Hairy leukoplakia in immunocompromised individuals

Interstitial pneumonitis and hepatitis in pediatric AIDS
patients.
 90% get cervical lymphadenitis- swollen lymph nodes and
pronounced tonsils.
o Human herpesvirus 6 (HHV-6)
 Causative agent of roseola infantum (sixth disease)
 Occurs between 6 months and 3 years of age
 Clinical syndrome
 Abrupt onset of high fever (104 degree C) that can be
associated with seizures
 Cervical lymphadenopathy
 Rash appears after 3-5 days.
 Can cause an infectious mononucleosis syndrome in older children
and adults
 Diagnosis
 Serology
 Treatment- Tylenol
 Roseola Infantum
 A non-specific maculopapular rash with a central
distribution developed on the third day of illness.
 Common in the spring and fall.
o Human herpesvirus 7 (HHV-7)
 Causes a disease similar to HHV-6. Generally the kids are older.
 Infection is usually acquired in early childhood
 Seroprevalence in most populations is >90%
 Virus can be isolated from saliva of seropositive individuals.
 Diagnosis
 serology
o Human herpesvirus 8 (HHV-8)
 HHV-8 was discovered as a result of the search for the etiologic
agent of Kaposi’s sarcoma.
 Distribution of this virus is worldwide with regional variation
 Africa and Italy KS is endemic and seroprevalence is ~60%
 North America and Northern Europe KS is rare and
seroprevalence is <10%
 Transmission is due to
 Maternal fetal transmission
 Sexual transmission (MSM)
 Diagnosis
 Serology
 Pathology
 KS
 Multiple violaceous lesions that can be any place in or
outside the body.
 Violet-purple rash/lesion.

HTLV-III: AIDS Virus or HIV
o ssRNA retrovirus, integrates into host genome, long latent period,
transmits by blood/body secretions.
o Marked depletion of T-helper cells.
o Immunosuppression occurs; opportunistic infections follow.
o Has been found in tears but there is no evidence for transmission through
the tears.
Antivirals

Have the same structure as DNA building blocks, allowing them to incorporate
into the viral DNA, preventing replication.
Idoxuridine (IDU) (Herplex, Stoxil)
 Dosing
o 0.1% solution
o 0.5% ointment
 General features
o Halogenated pyrimidine. Analog of thymidine. It contains an I- instead of
a CH3.
o Relatively insoluble in water and does not penetrate the cornea well.
 Mechanism: The triphosphate is incorporated into both cellular and viral DNA,
becoming phosphorylated by viral and human thymidine kinases, inhibiting
thymidine synthesis, thereby making fraudulent DNA. This blocks viral DNA
chain elongation
o Severe cytotoxicity, which is not as significant when topically applied.
 Indications
o Limited to DNA viruses, specifically members of the herpes virus group.
o HSV 1 infections
 Dendrites/geographic epithelial ulcers
 Sig: 1 drop q1h during the day and q2h during the night.
 Equivalent: 0.5% ung q4h during the day and qhs.
 With improvement
o 1 gtt q2h during the day and q4h at night.
o Continue 3-5 days after corneal healing. This is to
prevent recurrence.
o Treat maximum 21 days.
o 75% of patients cured in 2 weeks but does not
eradicate latent virus in trigeminal ganglion.
o No effect on recurrence rate of herpes keratitis.
 Primary herpes keratitis
 Same as above
 Administer until conjunctivitis/periocular skin lesions
resolve.

o No effect on herpes stromal disease or iritis. Treatment of herpes stromal
keratitis with high dose steroids require prophylactic (silmultaneous) use
of antiviral drugs- IDU
Adverse effects
o Acute effects- Stinging, lacrimation, and conjunctival hyperemia.
o Cornea
 If used for more than 21 days.
 Fine SPK, filaments, indolent ulceration
 Corneal filaments.
 Slowed epithelial healing and inhibition of stromal wound healing.
 Secondary superficial stromal opacification- “ghost” dendrites
 Pain, photophobia
o Conjunctiva
 Chemosis, hyperemia, filaments, punctate staining, follicles.
o Lid damage
 Edema, plugging of meibomian glands and occlusion of puncta.
Vidarabine-A (Vira-A)
 Dosing
o 3% ung
 General features
o Also called adenine arabinoside, it is an analog of the purine nucleoside
adenosine. It is more selective than idoxuridine, but is not widely used.
o Active against vaccinia virus, HSV (1 and 2), CMV, and VZV. Not
effective against RNA viruses.
 Mechanism of action
o Phosphorylated by viral and human thymidine kinases and metabolized to
triphosphate in infected cells. The triphosphate becomes incorporated into
viral DNA, inhibiting the viral enzyme DNA polymerase, making a
fraudulent DNA. This has a lesser effect on mammalian DNA synthesis,
because it is more selective.
 Indications
o Dendritic or geographic epithelial keratitis caused by HSV
 Vidaribine is as effective as IDU for the treatment of HSV
keratitis. it decreases new vesicle formation and has similar rates
and times for corneal reepithelialization (6-7 days).
 Sig: apply 3% ung 5x/day for a maximum of 21 days.
 Treatment should continue 5-7 days after corneal resolution.
o CMV
o VZV
o Vidarabine is approved for and is an effective treatment of HSV
encephalitis. Acyclovir is the drug of choice though.
o IDU, like vidarabine, is not proven useful for herpes simplex labialis or
genitalis.
 Side effects
o Stinging, burning, irritation, lacrimation, and injection
o Follicular conjunctivitis, marked SPK, corneal edema, corneal erosion,
trophic epithelial defects, delay of corneal wound and punctal occlusion.
o Compared with IDU, vidarabine is less toxic and has less adverse
reactions.
o If taken orally:
 GI upset, bone marrow depression, and neurotoxicity.
Trifluridine (Viroptic)- Trifluorothymidine, F3T
 Dosing
o 1% solution
o 3% ung is effective in dendritic herpetic keratitis and keratoconjunctivitis
induced by herpes zoster virus.
 General features
o It is an analog of thymidine, containing a CF3 group, not CH3.
o Effective inhibitor of thymidine sythetase. Triphosphate becomes
incorporated into the viral DNA, making a fraudulent DNA. It inhibits
DNA synthesis in both virus-infected and normal host cells
o Activated by herpes virus-induced thymidine kinase, and therefore normal
cells are spared disruption in nucleic acid synthesis even though it is
phosphorylated by viral and human thymidine kinases.
o Trifluridine is significantly superior to IDU and vidarabine
 Mean time for healing- 6.3 days vs. 8.2 days IDU
 Number of treatment failures 7.5% vs. 39.5% with IDU.
 Indications
o HSV keratitis and Thygesons SPK (Drug of choice)
 Sig: 1 gtt 9x/day x 14 days or until reepithelialization.
 Tapered to 1gtt q4h (awake) x 7 days.
 Avoid administering for more than 21 days.
o CMV and VZV infections
o As with IDU and Vira-A, trifluridine is effective for both primary and
recurrent epithelial keratitis
 Side effects
o Reversible on discontinuation
o Corneal epithelial defect at site other than infection, indicative sign of
drug toxicity.
o Mild, transient burning or stinging on instillation.
o Conjunctival hyperemia and edema
o Corneal erosion and edema, K. sicca, delayed corneal wound healing.
o Increased IOP
o Permanent ptosis, punctal occlusion, and conjunctival scarring.
o Compared to IDU and Vira-A, viroptic causes the least amount of local
irritation and toxicity
o In order: trifluridine is the first choice, then vidarabine, and lastly, IDU
since it is more toxic.
Acyclovir (Zovirax)




General Features
o Also known as acycloguanosine, it is an analog of guanosine. No 5 ring.
o Very little toxicity and short half-life.
o Highly selective
 Phosphorylation of acyclovir readily by herpes-specified thymidine
kinase in infected cells and not by uninfected host cell thymidine
kinase disrupts viral DNA replication in virus. Infected cells do not
disrupt DNA synthesis and replication of normal cells.
o This is the only one approved in CA for optometric use.
Mechanisms
o Monophosphorylated by viral thymidine kinase. Di and tri-phosphorylated
by cellular enzymes. Inhibition by the triphosphate of viral DNA
polymerase.
o Terminates viral DNA chain
o Binds to viral DNA and DNA polymerase
Preparations
o Suspension
o Ointment 3%
 Approved for treatment of primary genital herpes
o IV
 Effective for severe primary episodes
o Oral
 200, 800mg tablets.
 800mg 5x/day x 7 days for HZO.
 400mg 5x/day for active disease
 400mg 2x/day for suppression of recurrence of HSV
keratitis.
 As a long term suppressive agent
 Fewer recurrences occurred and longer times from onset of
treatment to recurrence
 Effective in suppressing frequently recurring nongenital skin
infections caused by HSV and erythema multiforme.
Side effects
o Minor- a very safe drug
o Most frequent adverse reactions from oral acyclovir include N, V, D,
vertigo, arthralgia, HA
o Less frequent reactions include skin rash, insomnia, fatigue, fever,
menstrual abnormality, sore throat, acne, lymphadenopathy, and GI
distress.
o Most frequent adverse reaction with IV acyclovir include inflammation of
phlebitis at injection site, rash or hives, and transient elevation of BUN
and creatinine
o Elevated renal function test results occur when acyclovir administered too
rapidly or to dehydrated patients. Slow infusion or increase patients water
intake can prevent renal abnormalities



o Most frequent adverse reactions with topical acyclovir include mild pain,
burning, stinging, and pruritis, along with SPK.
Indications
o During initial episode, oral administration can
 Decrease duration of viral shedding from genital lesions
 Reduce the development and healing time of new lesions.
 Decrease severity of symptoms such as pain, adenopathy, dysuria,
malaise, and Has
o Unfortunately, after discontinuation of acyclovir
 Time and rate of recurrence is not altered
 No permanent effect on the latent virus
 Treatment of recurrent lesions not as effective as primary infection.
o Very potent and effective antiherpetic agent (16 and 10x more active
against HSV than viroptic and IDU, respectively). Good for herpes
simplex, herpes zoster, and varicella zoster, genital herpes, herbes labialis.
o Drug of choice for biopsy-proven HSV encephalitis
o Treatment of ocular manifestations of HSV (herpetic dendritic ulceration).
o Treatment of acute retinal necrosis (ARN) characterized by triad of acute
confluent peripheral necrotizing retinitis, retinal arteritis, and vitritis (IV
acyclovir).
o Treatment of acute HZ in those with lymphoproliferative neoplasia or
organ allografts (IV acyclovir).
o Treatment of keratouveitis caused by VZV. Corneal epithelial lesions
resolved more quickly (topical).
o Effective against HSV (systemic and ocular) and VZV (HZO)
 Oral
 Sig: 800mg 5x/day x 10 days.
 Prompted resolution of signs and symptoms. There is a shortened
duration of viral shedding, especially within 72 hours after onset of
skin lesion. It also decreased the incidence and severity of
secondary ocular inflammatory disease, such as episcleritis,
anterior/posterior scleritis, stromal keratitis, and anterior uveitis.
There is no effect on post herpetic neuralgia.
o Useful in HSV disciform or stromal keratitis
 Acyclovir combined with steroid (topical).
Higher incidence of toxicity in the form of superficial punctate epitheliopathy
with IDU treatment
Topical acyclovir
o Sig: apply 3% ung 5x/day x 14 days
 As effective for treatment of HSV dendritic and geographic ulcers
as vidarabine ung.
 3% acyclovir ung compared to 2% trifluridine ung 5x/day
 rate of healing similar, but more dendritic ulcers treated with
acyclovir healed within 14 days.

Studies show that although acyclovir is effective for treating HSV epithelial
keratitis. It has no clearly demonstrable superiority over the currently over the
currently available antiviral drugs: IDU, vidarabine, or trifluridine.
Valcyclovir (Valtrex)
 Prodrug of acyclovir. Good alternate to it. It is the more effective oral form of
acyclovir. Plasma concentrations of acyclovir are greater than those obtained with
acyclovir administration. It may offer no breakthrough over Zovirax, except 35x/level of biograib as oral zovirax.
 Fastest onset and longer half-life.
 ADRs
o Similar to acyclovir.
 HZO: 2-500mg tab tid x 7 days, po
 HSV: 500mg tab tid x 7 days, po
Famcyclovir (Famvir)
 Prodrug of penciclovir. Pencyclovir is phosphorylated by viral thymidine kinase.
Inhibits herpes DNA polymerase. Alternative to acyclovir.
 Longer half-life. Most popular because it is the fastest onset. More expensive.
 Dosage for HZO is 500mg q8h. po
 Use: Acute herpes zoster infections.
 ADRs- Side effects similar to acyclovir.
 Use tid instead of 5x/day (as in acyclovir)
 Only FDA approved for shingles
 It has been shown to decrease duration of postherpetic neuralgia
o Effective against HSV and varicella
o Taken without regard to meals
o Metabolized by kidneys
Zidovudine (Azidothymidine, AZT, Retrovir, Zovirax)
 This is a thymidine analog that inhibits HIV replication in vitro
 Mechanism
o Phosphorylated by cellular thymidine kinase. As a triphosphate it inhibits
reverse transcriptase and terminates viral DNA elongation.
 Route of administration: oral.
 Indications of use
o Can decrease frequency of opportunistic infections, therefore decreasing
the mortality in selected AIDS patients. Approved by the FDA for the
treatment of patients with AID.
o CMV retinitis, anterior uveitism and iridocyclitis in AIDS patients
 Very toxic, because it can cause bone marrow hypoplasia/ depression. This leaves
some patients more vulnerable to bacterial infections.
Dihydroxypropoxymethylguanine (Ganciclovir) Cytovene





An analog of deoxyguanine, this is a cyclic nucleoside antiviral. It is similar in
structure to acyclovir.
Mechanism: Monophosphorylated by viral thymidine kinase; di and triphosphorylated by cellular enzymes. Inhibition by the triphosphate of viral DNA
polymerase.
IV administration, intravitreally (to stabilize infection), or as an intravitreal
implant, also orally (to follw-up with infection).
Indications
o CMV: 10-25x more effective vs. CMV than acyclovir. Shows regression
or disappearance of the exudative, hemorrhage, and periphlebitis lesions
of CMV retinitis
Adverse effects
o Bone marrow depression, causing neutropenia and thrombocytopenia.
o CNS toxicity
o Rash
o Fever
Phosphono Formic Acid (Foscarnet) Foscavir
 An analog of pyrophosphate, already in the active form.
 Mechanism: Blocks pyrophosphate receptor site of CMV DNA polymerase. This
drug inhibits viral DNA polymerases, viral RNA polymerases, and reverse
transcriptases.
 Route of Administration: IV
 Approved for treatment of CMV retinitis in AIDS patients who are unresponsive
to or intolerant of ganciclovir, but it is 2.5 times more costly than ganciclovir.
Foscarnot treatment prolongs life in AIDS patients more than gangciclovir. Can
also be used for HSV and VZV infections in AIDS patients.
 Patients do not tolerate Foscarent as well as gangciclovir due to fever, GI
problems, and renal impairment.
Vancyclovir- Treat genital herpes/ herpes labialis
Bromovinyldeoxyuridine (BVDU)
 Effective and safe compound for treatment of HSV-1 and VZV ocular infections.
 Phosphorylated only by viral thymidine kinase.
Didanosine (Videx)
 Also called dideoxyinosine (ddI); a purine analog
 Metabolized by cellular enzymes to 2’,3’-dideoxyadenosine triphosphate.
 Mechanism
o Inhibition of reverse transcriptase, causing the termination of viral DNA
chain
 Use: treatment of AIDS
 Route of administration: oral
 Adverse effects
o Systemic: Peripheral neuropathy
o Ocular: Pigmentary retinal lesions
Zalcitabine (Hivid)
 Also called dideoxycytidine (ddC); an analog of cytidine
 Metabolized by cellular enzymes to dideoxycytidine 5’-triphosphate
 Mechanisms
o Inhibition of reverse transcriptase, causing the termination of viral DNA
chain.
 Route of administration: Oral
 Adverse effects: Peripheral neuropathy
Ribavirin (Virazole)
 Aerosol form used to treat viral bronchopneumonia
Amantadine (Symmetrel)
 Possible mechanism: Inhibition of uncoating
 Use: Treat/prevent influenze A infection (with Parkinsons)
 Adverse effects- GI upset and insomnia
Rimantadine (Flumadine): Similar to amantadine
Trifluridine
Fluorocil- Treat cancer, kills viruses
Interferons
 Mechanism includes inhibition of viral protein synthesis, inhibition of viral
assembly, and stimulation of the immune system.
Immunoglobulins- Useful in treating hepatitis B and rabies infections.
Mycology

Characteristic of Fungi
o
o
o
o
o
o


Eukaryotic organisms
Most are obligate aerobes; some are facultative anaerobes
Major cause of plant diseases
Only small fraction of yeasts and molds cause diseases in humans
Prototypical yeast cell
Fungi include yeast, molds, and fleshy fungus.
 Yeasts are unicellular. Molds are multicellular and filamentous.
Pathogenic forms are dimorphic.
o They are non-photosynthestic.
o The four main groups are: Phycomycetes, Ascomycetes, Basidiomycetes,
and Deuteromycetes.
Structure
o Body (vegetative) structure is thallus
 Many fungal cells surrounded by chitin cell wall
 Consists of N-acetylglucosamine residues
Yeast and Mold Morphology
o The fungal cell wall consists primarily of chitin or some other
polysaccharide (not peptidoglycan as in bacteria), thus, fungi are
insensitive to antibiotics, such as PCN that inhibit peptidoglycan
synthesis.
o The fungal cell membrane contains sterols, ergosterol and zymosterol, in
contrast to human cell membranes which contain cholesterol. Therefore,
sterols are the target of selective action by antifungals such as
Amphotericin B.
o Growth
 Yeast grows as single cells that reproduce asexually by budding
and transverse division.
 Molds grow as long filaments (hyphae) and form a mat
(mycelium). Some hyphae form transverse walls (septate hyphae),
whereas others do not (nonseptate hyphae, therefore


multinucleated). This presence/absence of cross walls or septa in
the hyphae distinguishes different groups of fungi.
o Several important fungi are theramally dimporphic; i.e., they form
different structures at different temperatures. They exist as molds outside
the body (at lower temperatures) and as yeasts in host tissue (at body
temperature).
o Most fungi are obligate aerobes. Some are facultative anaerobes. But no
medically important fungi are obligate anaerobes. All fungi require a
preformed organic source of carbon, hence their frequent association with
decaying matter. All are termed chemoorganoheterotrophs (i.e., they use
organic matter as a source of carbon, electrons, energy). For biosynthesis
(anabolism) fungi use glycogen as the primary means to store
carbohydrates and use these, as well as various nitrogenous compounds, to
synthesize amino acids and proteins.
Growth Characteristics
o Yeasts grow as single cells
 Have single nucleus
o Molds grow as long filaments (hyphae)
 Hyphae is the basic unit of vegetative thallus or plant body,
threadlike structure.
 Mass of hyphae is mycelium
 Sometimes protoplasm and information streams through
hyphae despite the presence of cell walls.
o Coenocytic hyphae (without cell walls)
 Non-coencytic hypahae (septate) have cell walls (septa)
o Pores in septa allow protoplasmic streaming.
o Some fungi are dimorphic- capable of forming different structures at
different temperatures
 Shift from yeast (Y) form to mold/mycelial (M) form is called YM
shift
 Typical in animal hosts (Y) to environment (M)
 MY shift common in plants
 In M form in environment, spores are formed taken in by animals,
where it stays in the Y form.
o Most fungi are saprophytes obtaining nutrients from dead organic material
Reproduction
o Asexual reproduction is easy to determine; not sexual.
o Initially fungi classified due to reproduction, but sometimes both.
o Asexual reproduction can occur via fission (both parent and kid are the
same size), budding (common in yeasts), or the formation of asexual
spores. This is rapid, but not as rapid as bacteria.
 Sporangia form asexual spores
 Characteristics of these spores are important in classification of
fungi.
 Fragmentation of hyphae gives cells called arthroconidia or
athrospores
 Cells surrounded by thick cell walls are chlamydospores.
These can either be terminal, internal, or both.

Spores which develop within a sac at hyphal tip are
sporangiospores. These are released with contact.
 Spores not enclosed in a sac, but produced at tips or sides
of hyphae are conidiospores
o Example is PCN
 Spores produced by budding are blastospores
 Most fungi of medical interest propogate asexually by forming
conidia (asexual spores) from the sides or ends of specialized
structures. The shape, color, and arrangement of conidia aid in the
indentification of fungi.
o Sexual reproduction is via mating and formation of sexual spores
(zygospores, ascospores, basidiospores)





Characteristics of these spores are important in classification. They
take precedence over asexual reproduction
Some fungal species are self-fertlizing; others require outcrossing.
Sometimes there is a delay between cytoplasmic and nuclear
fusion leading to dikaryotic stage (2 nuclei in the same cell).
Gametangia form sexual gametes.
Some fungi reproduce sexually by mating and forming sexual
spores, e.g., zygospores, ascospores, and basidiospores.
Zygospores are single large spores with thick walls. Ascospores
are formed in a sac called an ascus. Basidiospores are formed
externally on the tip of a pedestal called a basidium. The
classification of these fungi is based on their sexual spores. Fungi
that do not form sexual spores are termed “imperfecti,” and are
classified as Fungi imperfecti.
o Yeasts
 Asexually by binary fission (budding).
 Sexual cycle is associated with the formation of asci which contain
from one to eight ascospores.
o Mold
 Reproduce asexually by conidia or sporangia which are fruiting
bodies.


Sexually by fertilization which involves union of two protoplasts
without the fusion of nuclei, stimulation to growth of ascogenous
hyphae and of haploid vegetative hyphae, or union of two haploid
nuclei in ascus.
Fungal divisions
o 4, based on sexual spore type produced
o Zygomycota
 Zygomycetes- common name.
 Lowest number of species
 Characteristics
 Hyphae are coenocytic (no septa)
 Asexual spores develop in sporangia at tips of aerial
hyphae (not resistant)
 Sexual reproduction produces tough, thick-walled zygotes
capable of withstanding harsh environmental conditionstravel, can remain dormant for many years.
 Rhizopus stolonifer- Black bread mold


o Ascomycota
Rhizoids reach into bread; stolons initially erect but arch
back forming rhizoids; other hyphae remain erect with
sporangia filled with black spores.
Usually asexual under adequate conditions; sexual when
stressed
o Fusion of gametangia forms thick, rough, blackcoated, dormant zygospore
o Upon germination, zygospore cracks open and
asexual sporangium are produced.





Produces ascospores
 There are 8 ascopores within each ascus.
Most numerous species
Ascomycetes- sac fungi
Characteristics
 Club or sac-shaped ascus
 Mycelium has separated hyphae (noncoencytic)
 Asexual reproduction common- formation of conidiospores
 Sexual reproduction requires formation of ascus
o Initial fusion of “male” mycelium (antheridium) or
cell with “female” mycelium (ascogonium) or cell.
o Eventually develops into asci
 Multiple asci in ascocarp
 Ascospores may be forcibly released from
ascocarp.
Claviceps purpurea
 Causes disease (ergot) in plants

Ergotism is toxic condition in humans that ingest fungus
o Symptoms include gangrene, psychotic delusions,
nervous spasms, convulsions
o Lysergic acid diethylamide (LSD) produced by
organism
o Also known as St. Anthony’s fire in Middle ages
o Thousands died
o Basidiomycota




Produce basidiospores
Basidiomycetes- club fungi (aka mushrooms)
Basidium involved in sexual reproduction
 Produced at hyphal tips
 Basidiospores produced in basidia
 Basidia may be held in basidiocarps
 Cryptococcus neoformans
 Responsible for cryptococcosis; systemic infection
affecting lungs and CNS. This is devastating to those with
decreased immunity.
o Deuteromycota
 Fungi Imperfecti- lack sexual phase (perfect stage)- not present or
not identified
 Several human pathogens causing athlete’s foot, ringworm,
histoplasmosis
Human pathogenesis
o Human infections can be grouped according to site and extent of invasion
by the pathogens- superficial, cutaneous, subcutaneous, systemic, and
opportunistic. The first three are not very dangerous.
o Superficial
 Malassezia, Piedraia, Trichosporon (some Tinea, hair and scalp)
 Mainly tropical; infect superficial structures (outer layers of skin,
nails, hair) but do not colonize any deeper tissues

Treatment with cleansing agent (topical); prevention with good
personal hygiene
 Dermatophyte infections (ringworms) invade only dead tissues of
the skin or its appendages (nails, hair, e.g., athletes foot). Causes
only mild or no inflammation, but may persist indefinitely, causing
acute infections later.
 Yeast infections (Candida or Moiliasis)
 Candida albicans, opportunistic infection, localized
infections common (thrush, vaginitis)
 Greater susceptibility in immunosuppressed. On antibiotic
therapy. Hematologic cancers. Diabetes.
 Two types of systemic infections.
o Endocarditis: affects damaged heart valves. Follows
heart surgery or inoculation by contaminated
needles.
o Upper GI tract candidiasis: follows antibiotic or
cytotoxic chemotherapy.
 Diagnosis: ocular chorioretinitis, vitreous haze, serologic
tests. Treat with Amphotericin B
 May shift from budding form to hyphae from upon tissue
infection. Appearance of these forms upon microscopic
exam is pathognomonic for candidiasis.
o Cutaneous
 Epidermophyton, Microsporum, Trichophyton (Some Tinea, jock
itch, athlete’s foot, ringworm)
 Dermatophytosis are superficial fungal infections that occur in
keratinized structures of the skin, hair, and nails.
 These are caused by fungi called dermatophytes.
 T: they are spread through direct contact with infected
persons or animals.
 PM and Sx: they are favored by heat and humidity, e.g.,
Tinea pedis (athletes foot) and tinea cruris (jock itch) are
characterized by pruritic papules and vesicles, broken hairs,
and thickened and deformed nails. The lesions are due to
the inflammatory response to the fungi.
 I: infection can sometimes produce hypersensitivity
reactions called dermatophytid (identify) reactions that
cause vesicles to appear on the fingers. These are due to the
immune response to circulating fungal antigens.
 Dx: patients with tinea infections show positive skin tests
with fungal extracts.
o Scrapings of skin or nail placed in 10% KOH on a
glass slide show hyphae under microscopy. Cultures
on Sabouraud’s agar at room temperature develop
typical hyphae and conidia.
 I: prevention centers around keeping skin dry and cool.


Tinea Versicolor and Tinea Nigra
Treatment with topical ointments of miconazole (Monistatderm),
tolnaftate (Tinactin), Clotrimazole (Lotrimin), Griseofulvin, and
Itraconazole (Sporanax).
 Griseofulvin is the top of the line, oral “last line of defense”
with many effects
o Subcutaneous
 Introduced into subcutaneous tissue through puncture wound
contaminated with soil; disease often takes years to develop
 These are caused by fungi that grow in soil and on vegetations and
are introduced into subcutaneous tissue through trauma.
 Sporothrix (sporotrichosis) most common subcutaneous in US
 This is a dimorphic fungus that lives on vegetation.
 Affects farm laborers, gardeners, and horticulturists.
Sporothrix schenckii found on rosebushes, moss, and
mulches.
 Primary lesion: usually on finger, small, movable, and
nontender. Advances to larger, necrotic, and later ulcerative
lesion.
 T: when introduced into the skin, typically by a thorn, it
causes a local pustule or ulcer with nodules along the
nearest lymphatic vessel.
 PM and Sx: no systemic illness occurs but lesions may be
chronic.
 Dx: in the clinical laboratory, round or cigar-shaped
budding yeasts are seen in tissue specimens. Oval conidia
are seen in clusters at the tips of hyphae (that look like a
daisy) when cultured.
 I: prevented by protecting skin when touching plants, moss,
and wood. Potassium iodide or ketoconazole is given orally
to treat the disease.
 Chromomycosis
 Slow, progressive granulomatous infection that occurs
mainly in the tropics and appears as wart-like lesions on the
legs and bare feet.
 Mycetoma (Madura foot)
 Suppurative abscesses form following contamination of
wounds by various fungi that live in the soil. Surgical
excision of infected regions is the only effective treatment.
 Infectious disease of the feet caused by a variety of soil
fungi.
 Characterized by swelling and granulomatous lesions of
subcutaneous tissues and multiple sinus formation.
 Early lesions are granulomatous but later are surrounded by
a dense capsule.

Months or years later, muscles, tendons, fascia, and bone
are destroyed.
 Treatment with oral 5-fluorocytosine, iodides, amphotericin B,
surgical excision
o Systemic
 Coccidioides (coccidiomycosis- valley fever), Histoplasma
(histoplasmosis), Cryptococcus (cryptomoccosis)
 Introduced by inhalation of spores of dimorphic fungi
 Inhalation of suffiecient numbers leads to lung lesion which
becomes chronic and allows spread of organisms through
bloodstream
 These infections usually begin in the lungs following inhalation of
the spores of dimorphic fungi. They exist as molds in soil but
within the lungs, the spores differentiate into yeasts or other
specialized forms. Most lung infections are asymptomatic and selflimited. However, some persons develop disseminated disease in
which the infection spreads to other organs, causing destructive
lesions, and may result in death. Noncommunicable from personto-person.
 Coccidiodes
 Dz: Coccidiodes immitis, a dimorphic fungus that exists as
a mold in soil and a spherule in tissue, causes
coccidiomycosis.
o Forms of infection
 Primary: acute, benign, self-limiting
respiratory disease. No treatment needed.
 Progressive: chronic, often fatal, infection of
the skin, lymph nodes, spleen, liver, bones,
kidneys, meninges, and brain.
 T: inhalation of airborn arthrospores.
 PM: in the lungs, arthrospores form spherules that are
large, have a thick, doubly refractive wall, and are filled
with endospores. Upon rupture of the wall, endospores are
released and differentiate to form new spherules. The
organism can spread by direct extension or via the
bloodstream. Granulomatous lesions can occur in any
organ, but primarily the bones and CNS are affected.
Usually host immunity confines the infection to the lungs
and protects the host from reinfection.
 Sx: infections of the lungs is often asymptomatic and is
evident only by a positive skin test and the presence of
antibodies. Some infected persons have an influenza-like
illness with fever and a cough. About 50% have changes in
the lungs as seen in xrays, and 10% develop erythema
nodosum as a hypersensitivity reaction. This syndrome is
called “valley fever” (from the San Joaquin Valley of CA).



Dx: in tissue specimens, spherules are seen
microscopically. Cultures on Sabourad’s agar show hyphae
with arthrospores. In infected person’s skin tests with
fungal extracts (coccidiodin or spherulin) become positive
2-4 weeks after infection and produce a delayed
hypersensitivity reaction within 48 hours. Since the skin
test is often negative in patients with disseminated disease,
serological tests (complement fixation for the detection of
antibodies) may be more reliable. In serological tests, IgM
and IgG precipitins appear within 2-4 weeks of infection
and then decline in subsequent months.
 I: no means of prevention other than avoiding endemic
areas.
Histoplasma
 Dz: Histoplasma capsulatum, a thermally dimorphic fungus
which exists as a mold in soil (low temperature) and a yeast
in the host (higher temperatures), causes histoplasmosis.
o Types of severe infections
 Acute: lasts 1 week to 6 months. Rarely
fatal.
 Acute-progressive: usually fatal within 6
weeks. Fever, loss of weight, cough.
 Chronic progressive: continue for years,
resembles chronic TB.
 T: in the US, it is an endemic in central and eastern states,
especially in the Ohio and Mississippi River valleys. It
grows especially well in soil heavily contaminated with
bird droppings. It causes histoplasmosis when spores are
inhaled.
 PM and Sx: Inhaled spores engulfed by macrophages
develop into yeast forms and reproduce by oval budding of
yeast. The organisms spread widely throughout the body,
but most infections remain asymptomatic because the small
granulomatous foci heal by calcification. It can be
progressive though.
 Dx: in tissue biopsies or bone marrow aspirates, oval yeast
cells within macrogphages are seen microscopically.
Cultures on Sabouraud’s agar show hyphae with macro
conida (thick walled spores with finger-like projections).
Skin testing using fungal extract (histoplasmin) is positive
2-3 weeks after primary infection.
 Treatment: no specific treatment. Rest and supportive care.
 I: no means of prevention other than avoiding endemic
areas.
Blastomyces Dermatitis

A dimorphic fungi, causes blastomycosis following
inhalation of spores present in the soil.
 Paracoccidioides
 A dimorphic fungi, causing paracoccidiomycosis. Fungus is
found only in Latin American soil.
 When symptomatic, almost always serious and often lifethreatening
 Treatment by amphotericin B, flucytosine, itraconazole,
miconazole, ketoconazole.
o Oppurtunistic
 Can show up when individual has an impaired immune system.
Fails to induce disease in most normal persons but may do so in
those with impaired host defenses.
 Almost always serious and can be life-threatening
 Aspergillus
 Dz: aspergillosis. This is the most common disease
producer in man. It is an opportunistic infection, colonizing
burns, external ear detritus, and bronchus.
o Two types
 Allergic bronchopulmonary
 Colonize in bronchi, treat with
steroids.
 Invasive aspergillosis
 Found in patients with cancer, grows
in necrotic tissue and spreads. Treat
with Amphotericin B.
 T: aspergillis species exist only as molds. They grow on
decaying vegetation. Transmission is by airborn conidia
through lungs.
 PM and Sx: aspergillis fumigatus can colonize the abraded
skin, wounds, burns, cornea, the external ear, or paranasal
sinuses. In immunocompromised persons, it can invade the
lungs and other organs, producing hemoptysis and
granulomas.
 Dx and I: biopsy aspecimens show septate, branching
hyphae invading tissue. Cultures show colonies with
characteristic radiating chains of conidia. In persons with
invasive aspergillosis, there may be high titers of
galactomannan antigens in the serum.
 Can lead to allergic aspergillosis, bronchopulmonary
aspergillosis, colonizing aspergillosis (“fungus balls” in
lungs)
 Can spread from lungs, causing death
 Treatment with itraconazole
 Candida (candidiasis)




Normal microbiota of GI and pulmonary tracts, vaginal
area, mouth (wide spread)- No problem unless
immunocompromised.
 Responsible for broad spectrum of human disease including
oral (thrush), napkin (diaper), candidal vaginitis.
 Dz: Candida albicans, a yeast and a member of the normal
flora, causes thrush, vaginitis, and chronic mucocutaneous
candidiasis.
 T: as a member of the normal flora, it is not transmitted.
 PM and Sx: When local or systemic host defenses are
impaired, diseases may result. Overgrowth of C. albicans in
the mouth produces white patches (thrush). Vulvovaginitis
produces itching and discharge, is favored by high pH,
diabetes, or use of antibiotics. Skin invasion occurs in wam,
moist areas, which become red and weeping. In
immunocompromised individuals, Candida may
disseminate to many organs or cause chronic
mucocutaneous candidiasis.
 Dx: in exudates or tissues, oval yeasts with a single bud or
long finger-like pseudohyphae are seen microscopically.
 I: no vaccine.
 No satisfactory treatment for infection although
ketoconazole, amphotericin B, fluconazole, itraconazole,
flucytosine can be used for mucocutaneous candidiasis.
Oral or topical antifungal drugs such as nystatin.
Pneumocystitis (Pneumocystis pneumonia)
 Occurs in >80% of AIDS patients
 Localized in lungs; causes alveoli to fill with frothy
exudates and decrease oxygen consumption.
 Treatment with oxygen therapy and
trimethoprim/sulfamethoxazole, atovaquone (Mepron),
inhalable pentamide.
o Treatment secondary infections and a couple of
antifungals.
Cryptococcus
 Dz and Tx: Cryptococcus neoformans is a yeast that causes
cryptococcosis when inhaled. The yeast is particularly
abundant in soil contaminated with bird droppings.
 PM and Sx: in an immunocompromised host, the organism
may produce an asymptomatic lung infection or
pneumonia. Disseminated disease also occurs affecting
other organs, particularly the CNS (meningitis).
 Dx: staining of spinal fluid with India ink shows yeast cells
surrounded by large unstained capsules. Serological tests
show presence of antibody and antigen in the spinal fluid.
Mucor





Rhizopus
Hospitalized patients with chronic antibiotics at risk
 38% die with candida
 95% die with aspergillus
 this is due to decreased immune and keeping the normal
microbiota from overgrowing. These “normals” keep up
healthy.
 About 25% of those with AIDS, chemotherapy, and organ
transplant get serious fungal infections.
Antifungal Chemotherapy
o Some are directed towards fungal membrane that contains ergosterol vs
our cholesterol as the principle sterol. Blocking ergosterol production
stops fungal growth.
o Amphotericin B- IV, increased toxicity, from streptomyces
o Diflucan (Fluconazole)- inhibits growth, but does not kill the fungus.
 Resistance seen with extended treatment
o Flucytosine is converted to fluorouracil by cytosine deaminase
 Fluorouracil inhibits thymidylate synthetase from converting uracil
to thymine
 Mammalian cells lack cytosine deaminase
o Griseofulvin accumulates in epidermis and other keratinized tissues
 Degraded by fungi as a nutritional source
 Inside fungi, it is thought to interfere with microtubule assembly
and disrupt mitosis
 Oral to treat epidermal chronic infections
 Problem with long-term effects
 Problem is that is does not work rapidly. They only inhibit the
growth, it needs to be used for several months/years for results.
o Nystatin- from Streptomyces- effective against Candida
Diagnosis
o Based on 3 approaches
 Direct microscopic examination
 Culture of the organism
 Serologic tests
o Specimens isolated from the appropriate sites of infection
 If from other place, it is not the cause.
o Use of Sabouraud’s agar to inhibit faster-growing bacteria
 Contains glucose and beef extract
 pH- 5.0 (specialized for fungi)
Laboratory isolation, culture, and identification
o There are three approaches in the laboratory diagnosis of fungal diseases
 Direct microscopic examination of clinical specimens such as
sputum, lung biopsy material, and skin scrapings to find
characteristic asexual spores, hyphae, or yeasts in the light
microscope. The specimen is either treated with 10% KOH to


dissolve tissue material, leaving the alkali-resistant fungi intact, or
stained with special fungal stains.
Culture of the organism on Sabouraud’s agar facilitates appearance
of slow-growing fungi by inhibiting the growth of bacteria in the
specimen. Inhibition of bacterial growth is due to the low pH of the
medium and the chloramphenicol and cyclohexamide that are
frequently added. The presence of mycelium and the nature of the
asexual spores are frequently sufficient to identify the organism.
Serological tests are useful in the diagnosis of systemic mycoses
but less so with other fungal infections. The complement fixation
test is most frequently used in suspected cases of
coccidioidomycosis, histoplasmoisis, and blastomycosis. In
cryptococcal meningitis, the presence of the polysaccharide
capsular antigens of Cryptococcus neoformans in the spinal fluid
can be detected by the latex agglutination test.
Fungus Pathology
 Candida- yeast causing mucosal/skin infections
o Most common
o Normal, commencial, but can have fungal overgrowths, i.e., with Ab
treatment. See pseudohyphae with yeast spores (budding)
o If seen in the esophagus, think HIV.
o Oral candidiasis (thrush)
 Trush is when it is just on the buccal mucosa, not on the back of
the throat.
 Can be seen on the cheeks as well.
o Candidal Balanitis
 More common with uncircumsized.
 Redness, but no white discharge.
 Dermatophytes- causing skin infections
o Cutaneous Ringworm
 Tinea Corpus
 Actually a fungus (no worm)
 Ring with central clearing
o Tinea Cruris
 Jock itch
 Hyperpigmentation
o Tinea Capitis
 On scalp
 Hair fallen out, scaly skin
 Deeper infection- skin feels mushy
 Needs oral treatment
 Wood’s lamp- fluorescence of fungus under black light.
 Tinea rubra fluoresces red.
o Tinea Pedis
 Athlete’s foot

Scaling, pus
Antifungal Drugs



Classifications
o Dermatophytic infections (Epidermophyton, Trichophyton, Microsporum,
cause Tinea, or Ringworm)
 Involve the keratinized portions of the body (skin, hair, nails).
o Mucotaneous infections (Yeast, candida)
 Affects moist skin/mucous membranes, such as the oral cavity
(thrush), GI tract, perianal, or vulvo-vaginal areas.
 Patients with DM, on corticosteroid treatment, on broad spectrum
antibiotic treatment, pregnant, or on oral contraceptives are
predisposed to yeast infections.
o Systemic (Deep or cutaneous)
 Enter by inhalation (aspergillous, blastomycosis,
coccidioidomycosis, cryptococcis, histoplasmosis, zygomycosis,
candidiasis, and paracoccidioidomycosis) or through traumatized
skin (chromomycosis, mycetoma, and sporotrichosis)
o Most frequent fungi cultured from mycotic corneal ulcers are Aspergillus,
Fusarium solani, Candida albicans and Acremonium (formerly known as
cepahlosporium).
Mechanism
o Bind to ergosterol of fungal cell membrane. This is not seen in
mammalian cells.
o Bacteriostatic and bactericidal
Polyene Derivatives- these contain many double bonds
o Mechanism of action

Binds ergosterol on membrane, forming ion channels in the fungal
cell membrane.
o Amphotericin B (Fungizone)
 Uses
 Drug of choice for treatment of systemic infections
resulting from coccidioides immitis, histoplasma
capsulatum, Cryptococcus neoformans, blastomyces
dermatitidis, and candida.
 Fungal corneal ulcers (IV or subconjunctival
administration).
 Fungal endophthalmitis (IV, subconjunctival, or intravitreal
administration).
 GI fungal infections
 Systemic candidiasis
 Treatment period can range from 6-10 weeks to as long as 3-4
months.
 Usually administered parenterally (IV) for deep seated infections.
 Dose and route of administration
 Sig: q1h during waking hours and q2-4hours at night
 Poor penetration through intact epithelium.
 Subconjunctival
o Results in permanent yellowing of cornea or
salmon-colored conjunctival nodules
 Intravitreally
o To treat fungal endophthalmitis
o Side effects are retinal damage and ocular
inflammation
 Future
o Amphotericin B methyl ester, a water-soluble
derivative of Amphotericin B
 Adverse effects
 HA, chills, fever, vomiting
 Renal damage due to ergosterol in renal cells.
 Retinal damage
 Moderate anemia
 GI cramps, hypomagnesemia, hypokalemia.
o Nystatin (Mycostatin)
 Uses
 Treatment of candida infections of the skin, mucous
membranes, intestinal tract
 Po indication (poor absorption in gut)- Oral, esophageal,
gastric, intestinal candiasis
 Topical indication- Vaginitis, stomatitis (thrush)
 Corneal infections (candida and aspergillus)- Fusarium
 Amphotericin B equally effective to Nystatin.

Side effects
 Mild and transient nausea, vomiting, diarrhea, and contact
allergic dermatitis
o Natamycin (Pimaricin, Natacyn)
 Uses
 Treatment of keratitis caused by Acremonium
(keratomycoses).
 Drug of choice for primary treatment in fungal keratitis
o Only FDA approved drug for topical treatment of
ocular fungal infections.
o Treatment of fungal corneal ulcers
 Sig: 1gtt of 5% suspension q1-2h
 Frequency reduced to 1gt 6-8x/day for the
first 3-4 days
 Treatment continued for 14-21 days or until
resolves.
 Available in 5% suspension. It is not systemically absorbed.
Topical application does not penetrate cornea, conjunctiva, or other
mucosal surfaces. Low levels reach the deep stroma or AC. Toxic
induration and lack of absorption preclude subconjunctival use.
 Natamycin greater effectiveness than Amphotericin B against
Fusarium
 Side effects
 Conjunctival hyperemia and chemosis.
o Flucytosine (Ancobon)
 This is fluorinated pyramidine. It is converted to fluorouracil in
fungal cells, then metabolized to 5-fluorodeoxyuridylic acid.
 Mechanism of action
 Inhibitor of thymidylate synthetase
 Fungalstatic/cidal
 Resistance high so it is used concomitantly with
Amphotericin B
 Oral administration
 Uses
 Systemic candida infections
 Systemic Cryptococcus neoformans infections
 Candida endophthalmitis
 Fungal keratitis
 Urinary candidiasis
 Readily absorbed after po ingestion and readily crosses the bloodbrain barrier.
 Side effects
 Bone marrow depression, hepatic damage, GI upset, N, V,
D, cerebral symptoms (confusion/hallucination)
 These are due to the fact that it can penetrate the blood
brain barrier.

o Primaricin
 Fungalstatic and fungalcidal
 Route of administration: Topical
 Use: Ocular infections
Imidazoles
o Good ocular penetration
o Mechanism
 Alters permeability of fungal cell membrane by inhibition of
ergosterol synthesis and damage to the fungal cell membranes.
 It can also inhibit cytochrome P450 and decrease testosterone.
 Fungicidal
o Choice of drug depends on type of fungus isolated and/or suspected.
o Miconazole (Monistat, Micatin)
 Background
 Fungistatic and fungicidal
 Broad spectrum agent. Candida and other yeasts, numerous
genera of filametous fungi, and dermatophytes
 Ocular uses
 Keratomycoses caused by candida and aspergillus (topical
and subconjunctival administration)
 Fungal keratitis
 Fungal endophthalmitis (intravitreal administration).
 Topical route
 2% ung effective for treatment of dermatophytosis,
candida, vulvovaginitis, and skin (tinea) infections
 IV route
 Treatment of deep infections caused by candida,
coccidioides, Cryptococcus, paracoccidioides, and
pseudallescheria.
 Sig: 1gt 1% q1h for several days
 Reduced to 1gt 6x/day.
 Subconjunctival administration
 Sig: 5-10mg daily x1-5 days
 Intravitreal injection
 To treat fungal endophthalmitis
 Adverse effects (all are minor)
 Pruritis, rash, chills, phlebitis, and GI symptoms
o Ketoconazole (Nizoral)
 Effective treatment for chronic superficial candidiasis and chronic
dermatophytosis and of systemic (deep) mycoses caused by
paracoccidioides, candida, and coccidioides. Cutaneous mycoses
 Treat fungal infections of the cornea. Treats keratitis caused by
aspergillus and fusarium (topical administration). Also treats
keratomycoses caused by several fungi (oral or oral plus topical
and subconjunctival administration).









Topical application is effective for treatment of keratitis due to
aspergillus and fusarium
 Sig: 1% solution
 PO alone or in combination with topical and subconjunctival
 Treatment of keratomycosis caused by fusarium,
aspergillus, drechslera, curvularia, and candida
 Adverse effects
 Hepatic toxicity (reversible), N, localized pruritis, HA,
dizziness, abdominal pain, constipation, diarrhea,
nervousness.
o Fluconazole (Diflucan) Crytococcal infections in AIDS patients
o Clotrimazole (Lotrimin) Candidiasis
o Econazole (Spectazole)
Drug of choice for prophylaxis and treatment of oropharyneal/esophageal
candidiasis
po
Effective against Cryptococcus; therefore, an addition contributor in the fight
against fungal infections that inflict many AIDS victims.
Effective in candida retinitis, uveitis, and endophthalmitis (Systemic
administration). Also keratomycosis (topical with or without systemic
administration).
Usually dose over age 14: 100-400mg qd
3-13 years: 1.3-2.6mg/lb qd
Side effects
o Nausea, HA, skin rash, vomiting, abdominal pain, diarrhea, liver toxicity
Topically- 0.2% has been used to treat keratomycosis
Other Various Antifungal Drugs
 Griseofulvin (Fulvicin, Grifulvin, etc)
o Oral, take many weeks
o Mechanism: Blocks polymerization of tubulin into microtubules
o Concentrates in keratin layer of skin
o Use: Dermatophyte infections
 Tolnafate (Tinactin, etc)
o Topical
o Use: Dermatophyte infections, e.g. athlete’s foot
o Fungicidal
 Terbenafine (Lamisil)
o Treats athletes feet by inhibiting ergosterol
o Fungicidal
Parasitology

Protozoa
o These are unicellular, heterotrophic eukaryotes that lack cell walls. They
are classified according to their organelle of motility: Mastigophore use
flagella. Ciliophore possess cilia. Amoeba use pseudopods. Sporozoa are
immobile.
o Reproduction is either by fission (asexual), conjugation or fertilization
(sexual).
o Usually cause human infections when ingested in the cyst form.
o Impact on humans
 Only 20 known genera of protozoa cause human disease
 Primary cause of morbidity and mortality
 More of a problem in 3rd world countries
o Medically Important Protozoa
Phylum
Group
Pathogen
Disease
Sarcomastigophora Amoeba
 Entamoeba
 Amebiasis, amebic
histolytica
dysentery
 Acanthamoeba
 Amebic
spp.
meningoencephaliti
s
Blood and
 Leishmania
 Cutaneous
tissue
tropica
leishmaniasis
Flagellates
 L. brazilienses
 Mucocutaneous
leishmaniasis
 L. donovani
 Kala-azar (visceral
 Trypanosoma
leishmaniasis)
cruzi
 American
 T. brucei
trypanosomiasis
gambiense
 African sleeping
 T. brucei
sickness
rhodesiense
Digestive and
 Giardia lambia
 Giardiasis
genital organ
 Trichomonas
 Trichomoniasis
flagellates
vaginalis
Apicompiexa
Coccidia
Cryptosporidium spp.
Crysptosporidiosis
Sporozoa
 Plasmodium
 Malaria
falciparum, P.
 Toxoplasmosis
malariae, P. ovate,
P. vivax
 Toxoplasma
gondii
o Classification
 Divided into 3 phyla
 Sarcomastigophora


o Flagellates and amoebas
Apicomplexa
o Sporozoans (multicellular)
Ciliophora
o Ciliates
 Cilia for movement and feeding
 Typical: Paramecium
 Simple, intracellular digestion
 Contractile vacuoles allow adjustment to
changes in osmotic pressure by taking
up/expelling water
 Single opening where material is drawn in
bu cilia, digestion occurs in vacuole,
nutrients leak out, and waste expelled.
o Pathogenicity
 Disrupt normal flora
 Local necrotic reactions
 Immune damage to tissues from intracellular infections
 Direct cell death, e.g., malaria anemias
o Intestinal protozoa
 Intestinal flagellates
 Use flagella for motility
 Giardia lamblia
o Giardiasis- most common cause of epidemic
waterborne diarrheal disease (30,000/year)
o Cysts ingested in contaminated water
 All water filters deal with this.
o As organism passes into colon, many cysts excyst
(open) to trophozoite
 Cysts present in stool
 Thick walled, resistant, 8-14 microns
in length
 Contain 2 or 4 nuclei
 Trophozoite is heart-shaped, 10-20
microns in length, 4 pairs of flagella,
2 nuclei
 Large sucking disk is used for
attachment to intestinal mucosa so
trophozoites rarely found in stool.
 Cysts not excysting in stool
 Thought to feed on mucosal
secretions
 May multiply to reach such numbers
as to interfere with nutrient
absorption (cover secretion of small
intestine)




Acute- severe diarrhea, cramps,
voluminous flatulence, anorexia
Chronic- intermittent diarrhea
Treatment with quinacrine
hoydrochloride (Atabrine) and
metronidazole (Flagyl) for adults;
furolidone for children.
Intestinal amebae
 Entamoeba histolytica
o Dz: Amebic dysentery and liver abscess.
o Infects large intestine
o LC: humans ingest cysts which form trophozoites in
small intestines. Trophozoites pass to the colon and
multiply. Cysts form in the colon.
o T: fecal-oral transmission of cysts. Ingestion of
cysts in food. Occurs worldwide, especially in the
tropics.
o PM: trophozoites invade colon epithelium and
produce “teardrop” ulcer. Can spread to liver and
cause abscesses/
o Sx: acute intestinal amebiasis presents as dysentery
(i.e., bloody, mucus containing diarrhea)
accompanied by lower abdominal discomfort,
flatulence, and tenesmus. Chronic amebiasis with
low-grade symptoms such as occasional diarrhea,
weight loss, and fatigue also occur. Amebic abscess
of the liver is characterized by right-upper quadrant
pain, weight loss, fever, and a tender enlarged liver.
o Dx: trophozoites or cysts in stool. Serology (indirect
hemagglutination test) positive with invasive
disease.
o I: none
o Present in 1 of 3 stages:
 Active amoeba, inactive cyst, intermediate
precyst
o Division

o Cysts present in lumen of colon and found in feces
 10-20 microns
o Cysts ingested, excystation occurs in lower region
of small intestine (colonization of large intestine)
o Trophozoites invade intestinal epithelium, multiply
rapidly, spread laterally and feed on erythrocytes,
bacteria, yeasts
o Active amoeba trophozoite is present in tissues and
found in fluid feces during disease
 With contact with human cells there is a
rapid influx of calcium, organelles lyse, and
cells die. The amoeba eats the dead cell or
absorbs the nutrients released.
 15-30 microns
o Produces proteolytic enzymes leading to lesions
(ulcers)
o Symptoms vary from asymptomatic infection to
fulminating dysentery, exhaustive diarrhea,
appendicitis, abcesses in liver, lungs, brain
o Treatment of asymptomatic cyst passers is
iodoquinol or paramomycin; amebaquin for carriers,
matronidiazole plus iodoquinol for symptomatic
individuals.
Intestinal Sporozoans
 Cryptosporidium species- spore formers contaminating
water


o Cryptosporidiosis- infection of
immunocompromised individuals
o Can cause severe intractable diarrhea
o Organism acquired from infected animal or human
feces or feces-contaminated food or water.
o Small (2-5 microns) intracellular spheres present in
large numbers under outer mucosal lining of
stomach or intestine
o Cyst very resistant to environment. As it moves
through the stomach, acid weakens the cyst wall. In
the small intestines, 4 motile sporozites emerge.
o Prominent clinical feature is diarrhea, along with
nausea and cramping
 Mild and self-limiting in immunocompetent
 Severe and prolonged in
immunocompromised, very young, or old.
o Treatment unnecessary for immunocompetent
patients; only supportive therapy is appropriate for
others
o Outbreak in Milwaukee
Urogenital tract protozoans
 Trichomonas vaginalis
o Trichomoniasis- infection of genitourinary tract in
both sexes
o Possess 3-5 flagella, characteristic undulating
membrane seen as it moves.
o Transmission via sexual intercourse.
o Capable of causing low-grade inflammation
o Pathogenicity determined by
 Intensity of infection
 pH and physiological status of vaginal and
GI tract surfaces
 Presence of bacterial flora
o In females, infection normally of vulva, vagina,
cervix
 Mucosal surfaces tender, inflamed, covered
with yellow or creamy discharge
 Profuse vaginal discharge
o In males, prostate, seminal vesicles, urethra
o Treatment of vaginal or prostatic infection with
systemic metronidazole (Flagyl), tinidazole
(Fasigyn), ornidazole (Tiberal)
Blood and tissue protozoa
 Blood and tissue flagellates (Hemoflagellates)
o Trypanosoma species


Trypanosoma brucei- African
trypanosomiasis (Sleeping Sickness)
 Vector is tsetse fly- parasites poresent in fly
feces
 Multiply at site of bite with variable
swelling
 Spread is to lymph nodes, bloodstream; in
terminal stages, CNS
 Toxin produced
 Sleeping sickness syndrome:
lassitude, inability to eat, tissue
waste, unconciousness, death
 Can be diagnosed and treated in
time.
 Treatment with suramin sodium (Germanin)
or pentamidine isethionate (Lomidine);
treatment of late stages adds melarsoprol
(MelB)
 Trypanosoma cruzei- American
trypanosomiasis (Chagas’ disease)
 Vector is triatomid (cone-nosed) bugparasites present in fly feces
 Enter into bloodstream, spread to
lymph nodes, spleen, liver, CNS
 Can destroy parasitized cells
 Toxin produced
 No effective treatment
o Leishmania species- leichmaniasis (diverse group of
diseases)
Blood and tissue sporozoa
 Plasmodium vivax, ovale, malariae, falciparum (deadliest)human malaria
o Although differences between species seen, life
cycle is similar
o Dz: malaria
o Malaria Epidemiology
 Humankind’s Greatest Killer
 This is the oldest recorded disease
 Appeared in Hippocrate’s 5th C medical
journals.
 Mid 1600s- Lima Peru- used tree bark to
treat  quinine
 2.3 billion at risk (2/3 of population)travelers, etc.
 300-500 million infected. 120 million cases.
1.5-3 million deaths/year
 US: 3,000 cases/year
 10 million travelers entering country and 23
million American’s at risk.
 Take appropriate prophylactic
antimalarials
 Increased resistance to chloroquinine
 Endemic around the equator and lower
hemisphere
 A lot of resistance.
o T: Bites from female Anopheles mosquito leads to
injection of sporozoites
 Sporozoites rapidly enter parenchymal cells
of liver from the circulatory system
 Numerous asexual progeny (merozoites)
leave liver cells and invade erythrocytes;
o
o
o
o
o
multiplication in liver cells can also
continue. They use the hemoglobin for
nutrients. The heme group is detoxified in
special organelles.
 After entering RBCs, become
differentiated to male or female
gametocytes
 Sexual cycle begins in host, but must
continue in female mosquito. They
go to the midgut leading to more
sporozoites that travel to the salivary
glands of the host.
Plasmodium falciparum infections usually the most
serious of the four, because sporozoan invades
blood cells of all ages and parasitized blood cells
produce projections which cause adherence to lining
of blood vessels.
LC: sexual cycle consists of gametogony in humans
and sporogony in mosquitos. Asexual cycle
(schizogony) occur in human. Sporozoites in saliva
of female Anopheles mosquito enter blood and
rapidly invade hepatocytes (exoerythrocytic phase).
Then they multiply and form merozoites.
Merozoites leave the hepatocytes and infect red
blood cells (erythrocytic phase). There they form
schizonts that release more merozoites, which infect
other red blood cells in a synchronous pattern.
Some merozoites become male and female
gametocytes, which, when ingested by female
Anopheles, release male and female gametes. These
unite to produce a zygote, which forms an oocyst
containing many sporozoites. These are released
and migrate to salivary glands.
PM: merozoites destroy red cells. Cyclic fever
pattern is due to periodic release of merozoites. P.
falciparum can infect red cells of all ages and cause
aggregates of red cells to occlude capillaries. This
can cause severe kidney damage (blackwater fever).
Hypnozoites can cause relapse.
Symptoms are characteristic- shaking chills, then
burning fever, sweating
Sx: malaria presents with abrupt onset of fever and
chills, accompanied by headache, mylagias, and
arthralgias, about 2 weeks after the mosquito bite.
Fever may be continuous eary in the disease. The
typical periodic cycle does not develop for several

days after onset. The fever spike, which can reac
42º C is frequently accompanied by nausea,
vomiting, and abdominal pain. The fever is
followed by drenching sweat.
o Toxin produced causing the symptoms
o Dx: organism visible in blood smear.
o Treatment with chloroquine (Aralen)prophylactically
 This blocks the detoxification of the heme
groups, so it kills the parasites.
 At this time there are no vaccines for
chloroquine resistance pathogens.
o I: -Toxoplasma gondii
o Dz: toxoplasmosis
 Four syndromes
 Acquired: usually asymptomatic
 Congential: result of transplacental
transmission. Hydrocephaly, mental
retardation.
 Retinochoroidal: usually late sign of
congenital infection.
 Acquired or reactivated in
immunosuppressed patients:
pneumonitis, myocarditis.
o Obligate intracellular parasite.
o Found in nearly all animals and most birds; cats are
definitive host and required for completion of
sexual cycle. Rats are intermediate hosts.
o Animals shed cysts in feces; cysts enter host
through nose or mouth; trophozoites colonize
intestine. Therefore, pregnant women should not
clean the litter boxes.
o LC: infections of humans begin with the ingestion
of cysts in undercooked mear or from contact with
cat feces. In the small intestine, the cysts rupture
and release forms that invade the gut wall, where
they are ingested by macrophages and differentiate
into rapidly multiplying trophozoites (tachyzoites),
which kill the cells and infect other cells. Cellmediated immunity usually limits the spread of
tachyzoites, and the parasite enters hose cells in the
brain, muscle, and other tissues, where they develop
into cysts in which the parasites multiply slowly.
These forms are called bradyzoites. These tissue
cysts are both an important diagnostic feature and a
source of organisms when the tissue cyst breaks in
an immunocompromised patient.
o T: T. gondii is usually acquired by ingestion of
cysts in undercooked meat or from contact with cat
feces. Transplacental transmission from an infected
mother to the fetus also occurs. Direct inoculation.
o PM: following infection of the interstinal
epithelium, the organisms spread to other organs,
especially the brain, lungs, liver, and eyes (retinitis).
Progression of the infection is usually limited by a
competent immune system.
o Most cases in immunocompetent individuals are
asymptomatic
o Infection frequently results in fatal systemic
infection in immunocompromnised people.
o Symptoms: lymph node swelling, pulmonary
necrosis, myocarditis, hepatitis, retinitis
o Sx: primary infection in immunocompetent adults
resembles infectious mononucleosis, except that the
heterophil antibody test is negative. Congenital
infection can result in abortion, stillbirth, or
neonatal disease with encephalitis, chorioretinitis,
and hepatosplenomegaly.
o 50% of the population carry cysts in the brain
without effects.
o Dx: immunofluorescence assay for IgM antibody is
used.
o Treatment with combination of pyrimethamine
(Daraprim) and sulfadizine
o I: progression of the infection is limited by a
competent immune system. Cell-mediated
immunity plays the major role, but circulating
antibody enhances killing of the organism.



Toxocariasis
o Aka visceral larva migrans
o Host is dog (toxocara canis) or cat (toxocara cati)
o Infections by ingestion of feces and/or contaminated soil
o Two types
 Acute: fever, cough, hepatomegaly, diagnose by serological
testing, treat with antihelmintic
 Ocular: granuloma of retina, treat symptoms with steroids and treat
disease with antihelmintic drugs.
Acanthamoeba
o Dz: meningocephaliutis, debilitating keratitis
o LC: trophozoite and cysts stages
o T: acanthamoeba is carried into the skin or eyes during trauma. Exposure
to contaminated water is another predisposing factor.
o PM: acanthamoeba infections occur primarily in immunocompromised
individuals.
o Sx: blurred vision, photophobia, tearing, severe ocular pain out of
proportion to the clinical findings are common findings of keratitis.
o Dx: finding amoebas in the spinal fluid. Three staining techniques are
commonly used on ocular samples
 Calcofluor
 Immunofluorescent staining
 Fluorescein conjungated lectins
o I: -Parasites can be any of the above. At some point in their life cycle live in or on a
host organism from which it secures some advantage.
o Often enters hosts (humans) via arthropod intermediate (vector).
o Other examples of multicellular parasites are nematodes (roundworm) and
cestodes (tapeworm).
Arthropoids
 Demodex: mite that parasitizes hair follicles and sebaceous glands in middle-aged
and elderly patients.
o Sx: morning ocular irritation and FBS
o Causes sheathing of clear debris along lashes, lash distortion, and loss.
 Phthirus, Pediculus
o Lice infestation
o Fecal material and saliva of louse are toxic and antigenic.
Helminths



Helminthes (parasitic worms: round, flat, liver flukes)
Multicellular animals (Metazoa) that parasitize humans and others
o From 1mm to several meters in length.
Nematode (Roundworms)
o These are elongated worms that have similar body plans (Ancylostoma
duodenale and Necator americanus)
 Dz: Hookworm
 LC: larvae penetrate skin, enter the blood, and migrate to the lungs.
they enter alveoli, pass up the trachea, then are swallowed. They
become adults in small intestine and attach to walls with teeth
(Ancylostoma) or cutting plates (Necator). Eggs are passed in
feces, form noninfectious rhabditiform larvae and then infectious
filariform larvae. Nematodes can also infect the liver, kidneys,
eyes, bloodstream, and subcutaneous tissue.
 T: filariform larvae in soil penetrate skin of feet. Humans are the
only hosts.
 PM: anemias due to blood loss from GI tract.
 Sx: weakness and pallor accompany the microcytic anemia caused
by blood loss.
 Dx: eggs visible in feces
o
o
o
o
o
 I: -Adults characterized by having elongate, cylindrical bodies (round in
cross-section)
Intestinal parasites including pinworms, roundworms. Found in soil,
transmitted from feces.
Have complete digestive tract, excretory, nervous, reproductive systems.
Surrounded by protective cuticle (integrument)
 Maturation requires shedding of cuticle
 Immature worm moves though series of molts (ecdyses)
 Egg  4 stages of larvae  adult
Various complex life cycle patterns seen
o Different ways an infection can occur depending on which part of the life
cycle is the infectious agent.
 Intestinal nematodes infective in egg stage
 Enterobius vermicularis- enterobiasis
o Pinworm or seatworm
o Very common infection (~500 million worldwaide)
o Most infections thought to be asymptomatic
o Life cycle
 Eggs ingested and hatch in small intestine
(larvae)
 Larvae migrate to large intestine
(cecum/colon) and attach superficially to
mucosa where they mature.



Larvae reach adulthood 2-4 weeks.
Infection usually lasts 1-2 months;
reinfection common.
o No specific immunity seen
 Females migrate to anus and emerge at night
to extrude eggs on perianal and perineal
skin.
 11-15,000 eggs before female dies
 eggs have sticky coating and adhere
to skin, hair, clothing, bedding
 Occassionally, females may enter vagina,
fallopian tubes, uterus, peritoneal cavity
(BAD!!!)
o Symptoms include anal pruritis, scratching may
lead to infection by bacteria or others
 Scratching also leads to reinfection as
contaminated fingertips or foods are placed
in mouth.
o Children may display insomnia, irritability, nausea,
nail biting
o Treatment with mebendazole or pyrantel pamoate
Ascaris lumbricoides
o Most common
o Estimated 800 million- 1 billion people infected.
o Found in tropical areas
o Large intestinal roundworm
o Infection due to ingestion of embryonated eggs in
food or drink
 Larvae then migrate but return to small
intestine, where they mature 8-10 weeks
after initial ingestion and stay for the rest of
their natural lives.
 Large adults (15-35cm) live unattached in
lumen of small intestine
 After sexual maturity, copulation, females
lay fertilized eggs- up to 200,000/day
 Pass from host in feces (source of
infection)
 Accidental ingestion of infective eggs- hatch
in duodenum, larvae penetrate intestinal
wall, enter circulatory system  lungs 
stomach  small intesting. The worm needs
to make this route to mature.
 Principle damage occurs in lungs, but other
major problems is from migration to
abnormal sites in body.


Hemorrhages are produced after
larvae enter alveoli; exudates with
prominent eosinophils collects.
 Dyspnea, dry cough, fever,
eosinophilia
 Ascaris pneumonitis includes
hemorrhage, cough, fever, and
eosinohilia (decreased numbers)
o Treatment during lung migratory phase is
supportive; pyrantel pamoate or mebendazole used
for intestinal ascariasis
Intestinal nematodes infective in larva stage
 Hookworms
 Necator americanus, Ancylostoma duodenale
o Adults about 1cm in length and reside in small
intestine
o 700-900 million worldwide
o Life cycle
 Adults worms attach to tip of villus sucking
blood from capillaries (=nutrients)
 After copulation, females lay eggs passed
with feces. These are in the undeveloped
state and do not die easily.
 Under favorable conditions. Eggs develop in
1-2 days  free-living larval stage
(rhabditiform). This is the feeding form.
 Feed on bacteria and detritus and eventually
metamorphose into infective (filariform)
larvae.
 Filariform larvae do not feed but can
live up to 2 weeks.
o Infection by larvae through any skin surface but
especially between toes
 Enter cutaneous blood vessels  right side
of heart  lungs  alveoli  epiglottis 
stomach  small intestine
o Some worms may live 10-15 years in humans, most
lost after 1 years (A. duodenale) or 4-5 years (N.
americanus)
o Symptoms include intense itching and burning at
site of entry, edema, erythema
o Most problematic is blood loss
 Can lead to anemia
o Treatment with mebendazole or pyrantel pamoate
 Trichinella spiralis
o 1-4% of Americans infected
o From pork
o Life cycle

No external phase (animal  human
infection)
 Both adults and larvae present in hosts
 Human ingest infective larvae
 Gastric digestion frees larvae which
enter small intestine and penetrate
mucosa.
 Adult stage, copulation, females burrow
deeper into mucosa or lower levels, release
larvae, all in 2 days
 Small larvae enter circulation, distributed
throughout body
 Only those entering striated muscle
capable of developing further
o Encapsulation triggered
mainly by host lymphocytes
and eosinophils  doublewalled capsule
o Infective in this form; viable
for extended periods of time.
o Vast majority of infection are asymptomatic, but
can have complications.
 Tissue destruction due to burrowing- nausea,
vomiting, diarrhea, fever
 Larvae in circulation lead to fevercharacteristic edema, especially around eye,


dyspnea, speech difficulties, hemorrhage,
especially in conjunctivae and retinal vessels
o Treatment usually supportive
Platyhelminthes (Flatworms)
Cestodes
o These are flattened, segmented worms, lacking a gut or mouth that live as
adults attached to intestinal walls of their hosts.
 Dx: Taenia saginata (beef tapeworm) causes taeniasis (Scolex has
four suckers but no hooks)
 LC: human ingests undercooked beef containing cysticerci.
Larvae attach to gut wall and become adult worms with
gravid proglottids. Terminal proglottids detach, pass in
feces, and are eaten by cattle. In the gut, oncospore
embryos hatch, burrow into blood vessels, and migrate to
skeletal muscles, where they develop into cysticerci.
 T: transmitted by eating raw or undercooked beef. Humans
are definitive hosts. Cattle are intermediate hosts. Occurs
worldwide but endemic in areas of Asia.
 PM: tapeworm in gut causes little damage.
 Sx: asymptomatic
 Dx: gravid proglottids visible in stool. Eggs seen less
frequently.
 I: -o Tapeworms- adult stage resembles a measuring tape
 Can be up to 10m in length
 Intestinal parasites. Transmitted to pigs from human feces, man
gets it from undercooked pork.
 Generally well-tolerated
 Usually major complaints absent until patient observes
proglottids in stool or having emerged from anus at other
times.
 Intestinal tapeworm infection should be treated.
 At anterior end is scolex, which is the attachment organ.
 Hooks, suckers, sucker-like grooves (bothria)



Adult tapeworm is composed of a joined chain (strobila) of
segments (proglottids)
 Each mature proglottid contains complete set of male and
female reproductive organs
No digestive tract present; nutrients absorbed directly through
body wall (tegument)
 Hooks, suckers, sucker-like grooves (bothria)
Posterior to scolex is germinal center (neck) from which new
proglottids arise
 Maturation of proglottids moves towards posterior end
o Groupings
 Immature, mature, gravid (proglottids full of
eggs)
 Gravid proglottids can detach and pass in stool

Life cycles of most tapeworms are very complex
 Most involve intermediate hosts
 Occasionally, humans can serve as host for the larval stage
o Situation can lead to severe disease state and death.
o Intestinal cestodes
 Hymenolepis nan- dwarf tapeworm
 Life cycle
o Adult is 2-4 cm in length
o Numerous adults usually present in infection
o Attaches to mucosa of small intestine
o Direct cycle
 Eggs are infective without an intermediate
host. (This is unique).
 Infection via hand to mouth or
ingestion of contaminated liquids or
foods.
 Eggs hatch in duodenum
o Embryos penetrate into
surrounding villi
o Larval stage (cystericercoid)
matures in 4 days and returns
to intestinal lumen, attaching
to the mucosa.
o Develop into adults in 2
weeks
o Adults live for months
o Indirect cycle
 Arthropods serve as larval hosts, especially
beetles
 Ingestion of arthropod containing
mature cystericercoids  infection.
 Some infections asymptomatic; others show diarrhea,
abdominal discomfort, anorexia.
o Heavy infections show profuse diarrhea, intense
abdominal pain, pruritis, nervous disorders, apathy.
 Treatment is difficult; niclosamide (Yomesan), and
praziquantel (drug of choice)
 Taenia saginata- taeniasis
 Beef tapeworm
o Infection due to ingestion of raw or insufficiently
cooked beef
 High prevalence of infection in Kenya, Ethiopia, Taiwan,
Phillipines, Iran
 Life cycle
o Adult worm attaches to mucosa of small intestine
via scolex (usually 1/infection)
o Distal gravid proglottids detach from strobila and
migrate out of anus or pass in stool
 Grazing cattle can ingest proglottids or eggs
released upon disintegration of the
proglottids
 Embryos emerge from eggs in
duodenum and penetrate into
intestinal tissue.
 Enter into circulation to skeletal
muscles or heart.
 Transform into cysticercus larval
stage- infective for humans (60-75
days)
o Humans ingest larvae in raw or inadequately
cooked beef
 Larvae attaches to wall of ileum
 Adult worms (8-10 weeks) can reach 5-10m
in length and live several years.
 Most infections are asymptomatic
o Often detected when proglottids seen in stool
o Abdominal discomfort, hunger pains, diarrhea,
anorexia, weight loss seen.
 Treatment is with niclosamide or praziquantel
 Taenia solium- taeniasis
 Pork tapeworm
 Infection from eating raw or inadequately cooked pork
 Humans can serve as intermediate or definitive host
 Life cycle
o Adults attch to mucosa of small intestine via scolex.
Release gravid proglottids into stool.
 Clinical manifestations of adult infections are same a T.
saginata
 Treatment with niclosamide or praziquantel
o Tissue Cestodes
 Cysticercosis
 Both larva and adult forms in humans
 Most often caused by larvae of Taenia solium (Cystericus
cellulosae)
o Predilection for skeletal muscles and nervous
system.
 Most common in Mexico, Thailand, eastern Europe where
T. solium-caused taeniasis is endemic
 Eggs are infective agents
 Routes of infection
o External autoreinfection


Person harboring adult worm nay transfer
mature eggs from anus to mouth on
fingertips.
o Heteroinfection
 Transfer of mature eggs from anus of person
harboring adult worm to new individuals via
fingertips.
o Internal autoreinfection
 Thought that detached gravid proglottids
transferred by reverse peristalsis into more
proximal areas of small intestine
 Eggs hatch to release larvae
 Cysticerci especially dangerous when involvement of eyes
and brain
o Ocular cysticercosis- uveitis, retinal dislocation,
pain
o Cerebral cysticercosis- HAs, vomiting, impaired
vision, convulsions, epileptic seizures
 Cysticerci can live 3-5 years
 Treatment with praziquantel
Trematodes- Flukes- parasitic flatworms
o Important Trematodes of Humans
o Flatworms that exhibit bilateral symmetry and have one or two suckers
(Clonorochis sinensis)
 Dz: Clonorchiasis
 LC: humans ingest undercooked fish containing encysted larvae
(metacercariae). In duodenum, immature flukes enter biliary duct,
become adults, and release eggs that are passed in feces. Eggs are
eaten by snails. The eggs hatch and form miracidia. These multiply
through generations and then produce many free-swimming
o
o
o
o
o
cercariae, which enxyst under scales of fish and are eaten by
human.
 T: by eating raw of undercooked freshwater fish. Humans are
definitive hosts. Snails and fish are first and second intermediate
hosts, respectively.
 PM: inflammation of biliary tract.
 Sx: most infections are asymptomatic. In patients with a heavy
worm burden, upper abdominal pain, anorexia, hepatomegaly, and
eosinophilia can occur.
 Dx: made by finding the typical small, brownish, operculated eggs
in the stool.
 In some infections, the inflammatory response can cause
hyperplasia and fibrosis of the biliary tract.
Transmission from raw food. Adult worms, secretions, and eggs cause
tissue destruction, inflammation, and hemorrhage.
Sexual reproduction in vertevrate hosts; asexual reproduction in snails
(intermediate)
Adults usually flat, elongated, leaf-shaped
 One to several cm in length
 May live for several years
Among trematodes, only blood flukes are not hermaphroditic
Schistosomes or blood flukes




Schistosomiasis- also known as bilharziasis or snail fever
Schistosoma japonicum, schistosoma mansoni, schistosoma
haematobium
Separate sexes
Adult worms in pairs in mesenteric or vesical veins on outside wall
of intestines or urinary bladder
 Males attach to wall of blood vessel, holding female who
releases eggs.
o Eggs are undeveloped when laid but fully
developed ciliated larva is present shortly thereafter
o Pass in stools or urine
o In freshwater, eggs hatch and larvae swim
 If appropriate snails present, will penetrate
into host.
o After several weeks, cercaraie released into water
o When contact with humans or other hosts, discard
tails and penetrate skin- schistosomula
o Enter bloodstream  heart  lungs  heart 
large arterial vessels
 Along route, feed and grow, reach sexual
maturity, and migrate to site of egg-laying.


Many different problems depending upin organism,
different stages, sites of infection, etc.
o Penetration of skin- hemorrhage
o Damage to lung capillaries- acute inflammatory
response
o Toxic manifestations- fever, sweats, epigastric
distress, pain in back, legs, groin, diarrhea
o Damage to intestines in the form of trauma and
hemorrhage
o Liver damage, urinary bladder damage
Chronic schistomiasis of the bladder linked to SCC
Treatment with praziquantel


Antihelminthic drugs
o Niclosamide (tapeworms) inhibits ATP production under aerobic
conditions. It uncouples ox phos
o Praziquantel (tapeworms, some flukes) alters worm plasma membrane
permeability

Leads to muscular spasms and worms become susceptible to
immune system
o Mebendazole [ascariasis (Ascariasis lumbricoides), pinworms (Enterobius
vermicularis), whipworms (Trichuris trichiura)]- disrupts microtubules in
cytoplasm indirectly interfering with ATP production from carbohydrates
o Pyrantel pamoate (pinworms, hookworms, ascariasis) paralyzes worms
leading to exit from body.
Antiprotozonal Drugs

Combined to treat acanthamoeba (not effective against cysts)
o Propamidine (Brolene- available in England and obtained with FDA
approval). Usually combined with neomycin
 Trophozoicidal , but poorly cysticidal
o Imidazoles (Clotrimazole, miconazole, itraconazole)
 Clotrimazole can be formulated with artificial tears from a powder
with FDA approval.
o Polyhexamethylene biguamide (pool-cleaning product = Baquacil)
 Dilute to a 0.02% solution with artificial tears. Used topically.
 Kills both trophozoites and cysts in vitro
 Less toxic than neomycin and propamidine
Ocular Infections
 Introduction
o Ocular infections run gamut from relatively mild episodes of
conjunctivitis and blepharitis up to keratitis and endophthalmitis.
 Any organism capable of gaining entry can cause disease
 Bacteria, viruses, fungi, protozoa
 Certain organisms can invade and penetrate intact
epithelium of conjunctiva or cornea.
o Otherwise, intact epithelia are very effective border.
 Protection of ocular structures is due to normal microbiota,
defensive strategy embracing local/systemic strategies,
specific/nonspecific, humoral/cellular mechanisms
 Many factors involved in susceptibility/resistance to infection and
which organisms will be involved
 Time of year, climate, age of patient, underlying diseases,
general health
 Microbial Flora of the Lids and Conjunctiva of the Normal Eye


Ocular Structures
o All are possible sites of infection
 Conjunctiva, lids, cornea, sclera, orbit, lacrimal apparatus, anterior
chamber, vitreous chamber, uveal tract, retina.
o The vast majority of flora from noninflamed eyes consists of coagulasenegative staphylococcal species and diptheroids
 Potential pathogens also make up part of normal microbiota
 Staphylococcal aureus, streptococcus pneumoniae,
Haemophilus influenzae
 Some members of normal microbiota produce antimicrobial
compounds which inhibit the growth of other potential pathogens
Infections of the conjunctivae (conjunctivitis)
o Red eye most common of all ocular symptoms
 May be acute or chronic
 Usually of bacterial or viral origin
o Bacterial

Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus
influenza, Streptococcus sp., members of Enertobacteriaceae,
Neisseria gonorrhoeae, N. meningitides, Propionibacterium acnes,
Staphylococcus epidermidis, Corynebacterium sp., Pseudomonas
aeruginosa, Proteus mirabilis, Chlamydia trachomatis
 Adults
 Warmer climates- S. aureus
 Cooler slimates- S. pneumoniae
 Infants, children
 H. influenzae, Streptococcus sp., members of
Enterobacteriaceae, N. gonorrhoeae, C. trachomatis
 Infants acquire N. gonorrhoeae (neonatal gonorrheal
ophthalmia), C. trachomatis (neonatal inclusion
conjunctivitis) as they travel down infected birth canal.
o Antibiotics routinely given to prevent infection.
 Instillation of contaminated cosmetics and medications- S. aureus,
S. epidermidis, Corynebacterium sp., P. aeruginosa, P. mirabilis.
 Hyperacute- N. gonorrhoeae, N. meningitides
 Large amounts of exudates that runs down face
 Adults probably acquire gonococcal conjunctivitis via selfinoculation; meningococcal conjunctivitis via contagious
spread from respiratory tract
 Chronic- coagulase-negative staphylococcal sp., S. aureus, P. acnes
 Trachoma- chlamydial origin
 Most common preventable blindness in world.
 Initial infection/propagation on conjunctivaea
 Can lead to conjunctival scarring, damage to cornea,
eyelids  blindness
 Culture/smears from conjunctival scrapings in acute cases; less
utility in chronic cases
o Rickettsia
 Conjunctiva often portal of entry for Rocky Mountain spotted
fever, scrubtyphus, Q fever, endemic murine typhus, Marseilles
fever
 Usually mild but can be severe complication of systemic
disease
o Treatment with chloramphenicol or tetracycline.
o Viruses- viral conjunctivitis
 Acute of chronic
 Acute- adenoviruses, herpesviruses, enteroviruses
 Adenoviruses
o EKC very contagious- serovars 8, 19 (to a lesser
degree 7, 9, 10, 11, 14, 16)
 Often spread by physicians, direct contact,
fomites


Outbreaks seen in ophthalmicoffices/clinics,
school locker rooms, dormitories
o PCF- serovar 3 (1, 2, 4, 5, 6, 8, 14)
 Both syndromes are self-limiting- EKC 3-4
days, PCF 10 days
 Herpesviruses
o Herpes simplex blepharoconjunctivitis
o Responsible for majority of severe ocular viral
infections
 >90% due to HSV I, rest from HSV II and
VZV
o Usually occurs in young children
 Enteroviruses
o Acute hemorrhagic conjunctivitis (AHC), epidemic
hemorrhagic conjunctivitis (EHC)
 Acute, short-lived infection- enterovirus 70,
coxsackievirus A24 (adenovirus 11)
 Self-limiting- 5-7 days, highly
contagious.
o Fungi- fungal conjunctivitis
 Rare event- Candida, Sporothrix schenckii recovered in cases of
fungal conjunctivitis
 Systemic infections with Coccidioides immitis,
Histoplasma capsulatum, Cryptococcus neoformans can
also extend to the conjunctival tissue.
o Parasites- rare; usually secondary complication
 Loa loa- “Eye worm”
 Migration of adult worms into subcutaneous tissues and
blood vessels.
Infections of the lids (Blepharitis)
o Can be in concert with infection of the conjunctiva
o Bacteria
 S. aureus, coagulase-negative staphylococcal sp., Moraxella
lacunata, Bacillus anthracis, Actinomyces spp., Mycobacterium
tuberculosis, Mycobacterium leprae
 S. aureus and coagulase-negative staphylococcal sp. most
commonly isolated from lid margins- mixed infection
 Blepharitis is low-grade inflammation usually associated with
functional disease of the seborrheic glands (seborrheic blepharitis)
 Dry (staphylococcal) and greasy (seborrheic) scales
attached to lashes- ulcerations cause lashes to fall out.
o Treatment of staphylococcal infection with
antibiotics
 Acute infection of glands in lids results in formation of hordeolum
(stye)


Treatment with hot soaks; supplemental with topical
erythromycin or tetracycline
 M. lacunata responsible for “angular blepharitis”, infection of lid
angles
 B. anthracis, Actinomyces sp. also responsible for lid infections
 M. tuberculosis infection leads to lid ulceration, M. leprae
(leprosy) leads to loss of eyebrows and lashes.
o Viruses- viral blepahritis
 HSV I or II, VZV, pozvirus, papovirus, vaccinia
 HSV usually during early childhood
o Vesicles appear on lid margins and skin around eye,
break open and form crusted secondary lesions.
 VZV during chickenpox episodes
o Vesicles on upper or lower lid margins
 Vaccinia due to direct inoculation with smallpox
vaccination
o Fungi- fungal blepharitis
 Very rare- result of systemic disease by Candida sp., Blastomyces
dermatitidis
o Parasites- usually due to complications and spread from adjacent sites
 Cutaneous leishmaniasis, African or American trypanosomiasis,
Loa loa infections, dirofilariasis
 Crab or pubic louse (Phthrius pubis) infests cilia and lid margins
Infections of the cornea (keratitis)
o Infection can progress though the 5 layers of the cornea
 Very few organisms can cross an intact epithelium
 Once compromised, any organism can launch infection
o Scarpings for smears and cultures must be taken.
o Bacteria
 P. aeruginosa, S. aureus, S. epidermidis, Serratia marcescens, P.
mirabilis, S. pneumoniae (less frequently), N. gonorrhoeae,
Moraxella sp., Corynebacterium diptheriae, Streptococcus viridans
group, Mycobacterium sp., Nocardia sp., Chlamydia sp.
 Geographical variations
 P. aeruginosa extremely dangerous
 Produces enzymes which liquefy corneal tissue within 2448 hours.
 Most frequent isolate from CL-associated keratitis
 Antibiotic treatment based on infecting organism
 CL isolates other than P. Aeruginosa
 Serratia marcescens, Achromobacter xylosoxidans, S.
aureus, etnterobacter cloacae, klebsiella pneumoniae, S.
epidermidis, pseudomonas, bacillus sp., mycobacterium
triviale/other MOTT, acanthamoeba sp., free-living amebae
other than acanthamoeba, curvularia sp., penicillium sp.,
aspergillus sp., candida sp.




P. aeruginosa is the prevailing organism in CL-associated
keratitis.
These organisms have been isolated predominantly from
soft (DW, EW, and disposable) lenses, lens cases, and
solutions. HCL are less involved in this type of keratitis.
The best preventative measure for avoiding this potentially
catastrophic ocular disease is to follow the physician’s and
manufacturer’s guidelines for wearing and caring for CL
and solutions.
o Viruses
 HSV most common and severe
 Can be due to direct inoculation or reactivation of latent
virus in trigeminal ganglion.
 Mainly HSV I but HSV II also involved
o Ocular lesions indistinguishable
o Treatment includes debridement, topical acyclovir
 Herpes zoster ophthalmicus (VZV) due to reactivation of
latent virus first presented as chickenpox
o In adults, ocular zoster is painful, severe, sometimes
blinding.
o Treatment with oral and topical acyclovir
 Adenovirus infections, measles, rubella, mumps, EBV infection,
Newcastle disease can all have corneal involvement
o Fungi
 Fusarium solanae, F. oxysporum, Curvularia sp., Paecilomyces sp.,
Aspergillus sp., candida albicans, C. parapsilosis, C. tropicalis
 Usually some history of trauma with soil or plant material
 Treatment with topical antifungals.
o Parasites
 Acanthamoeba sp., Naegleria sp., Vahlkampfia sp., Microsporida
 Amebic keratitis- often mistaken for viral or fungal keratitis
 Acanthamoeba species most common
 Originally seen with use of homemade saline solutions
o Now lesser risk factor
 After culturing, direct detection of cysts and trophozoites
 Microsporidian keratitis is emerging disease of AIDS patients
 Obligate intracellular parasite infects conjunctivae and
corneal tissue
 No uniform treatment
 Onchocerca volvulus- onchocercosism river blindness
 About 18 million in Africa, South and Central America
 Transmission by bite of black fly
Infections of the sclera and episclera (scleritis and episcleritis)
o Usually local manifestation of systemic connective tissue disease or result
of contigous spread from adjacent ocular tissues
 Can be acute (pyogenic) or chronic (granulomatous)


o Bacteria
 S. aureus, P. aeruginosa, S. marcescens, other members of
Enterobacteriaceae, S. pneumoniae, Moraxella sp., Mycobacterium
sp., Treponema pallidum
 Mycobacterium sp., Treponema pallidum involved in chronic
disease. Others acute.
o Viruses
 HSV, VZV, mumps
 Usually result of corneal or systemic extension of disease
o Fungi
 Paecilomyces sp., Aspergillus sp., Fusarium sp., Curvularia sp.,
Sporothrix sp., Blastomyces sp.
 Usually result of corneal or systemic extension of disease
o Parasites
 Rarely seen but due to progression of infestation.
Infections of the orbit (preseptal and orbital cellulitis)
o Microorganisms gain access via trauma or injury to eyelids or orbit.
o Bacteria
 S. aureus, S. pneumoniae, Streptococcus pyogenes, H. influenzae
(less often), Mycobacterium sp., Nocardia sp., S. epidermidis,
Actinomyces sp., Capnocytophaga sp., P acnes
 Adults- S. aureus most common
 Children- H. influenzae
 Chronic orbital cellulitis may be caused by Mycobacterium sp.,
Nocardia sp., Actinomyces sp.
 Bacterial infections associated with orbit implanyts and protheses
lead to recovery of Mycobacterium chelonae, Nocardia sp., S.
epidermidis, Capnocytophaga sp., P. acnes
o Fungi
 Member of Zygomycetes subclass and Aspergilllus sp.
 Often isolated from immunocompromised patients with underlying
disease
 Other fungi may also be involved.
o Parasites
 Trichinella spiralis, echinococcus granulosus
 Trichinosis can invade EOMs and cause periorbital edema with
pain on movement
 Invastion of ocular muscles often first sign of disease
Infections of the lacrimal apparatus
o Main lacrimal gland
 Infection may come from the blood stream
 Blunt trauma can also predispose the components to infection
o Infection of tear sac often associated with obstruction of nasolacrimal sac
o Bacteria
 N. gonorrhoeae, S. aureus, Streptococcus sp., C. trachomatis,
Actinomyces israelli, Actinomyces sp., Proprionobacterium

propionicus, P. acnes, Nocardia sp., Fusobacterium sp.,
Capnocytophaga sp., S. pneumoniae, S. pyogenes, H. influenzae,
P. aeruginosa, P. mirabilis, Mycobacterium sp.
 Lacrimal gland- dacryoadenitis
 Acute infection of lacrimal gland recovers N. gonorrhoeae,
S. aureus, Streptococcus sp.
 Chronic infections involve tuberculosis, syphilis, leprosy
 Canaliculi
 Canaliculitis is low-grade inflammation affecting lower
canaliculi more than upper
 S. aureus, Streptococcus sp., various Gram-negative rods,
C. trachomatis, Actinomyces israelli, Proprionibacterium
propionicus, P. acnes, Nocardia sp., Fusobacterium sp.,
Capnocytophaga sp.
 Tear sac- dacrocystitis
 Most common infection of lacrimal apparatus
 S. aureus, S. pneumoniae, S. pyogenes, H. influenzae, P.
aeruginosa, P. mirabilis, Actinomyces sp. isolated from
acute infections
 C. trachomatis may cause recurrent, chronic inflammation
o Viruses
 Mumps virus, EBV, HSV, VZV, CMV, coxsackievirus A,
echovirus, measles virus, influenze virus,
 Lacrimal gland
 Mumps virus and EBV most common
 Subclinical or inapparent infections seen with HSV, VZV,
CMV, coxsackievirus A, echovirus, measles virus,
influenza virus
 Canaliculi
 HSV, VZV
o Fungi
 C. albicans, Candida sp., Aspergillus sp.
 C. albicans, Aspergillus sp. isolated from inflamed canaliculi
 Aspergillus sp., Candida sp. may be recovered from inflamed tear
sac
o Parasites
 Schistosoma haematobium, onchocerca volvulus, cysticercus
cellulose
 Schistosoma haematobium, onchocerca volvulus, cysticercus
cellulose have been reported as invading the lacrimal gland.
Infections of the intraocular chambers (endophthalmitis)
o Can involve both anterior and vitreous chambers
o Bacteria
 Coagulase-negative staphylococci sp., S. aureus, P. acnes,
Streptococcus viridans group, Enterococcus sp., Bacillus cereus,
Bacillus sp., H. influenzae, P. aeruginosa, S. marcescens, P.


mirabilis, Morganella morganii, Citrobacter diversus, M. chelonze,
Nocardia sp., Actinomyces sp.
 Coagulase negative staphylococcal sp., S. aureus, P. acnes,
Streptococcus viridans group, Enterococcus sp. are top five.
 Bacillus cereus, Bacillus sp. usually isolated from endophthalmitis
resulting from traumatic insults.
 Presentation is sudden; course is fulminant
 Necrotizing enzymes can result in loss of eye within 48
hours.
 Staphylococcal and streptococcal species are most common
isolates from postsurgical cases
o Viruses
 HSV, VZV, CMV
 Usually manifest as retinitis or chorioretinitis
o Fungi
 C. albicans, Candida sp., Aspergillus sp., Fusarium solani,
Paecilomyces sp., Curvularia sp., S. schenckii, others
 Most often result of extension of keratitis
 Can also result from hematogenous spread from remote focus and
from implantation of contaminated intraocular lens
o Parasites
 Onchocerca sp., Toxocara sp., Toxoplasma gondii
 Usually affect the retina or choroids- transient invaders
Infections of the uveal tract (uveitis)
o Bacteria
 M. tuberculosis, T. pallidum, M. leprae, Nocardia asteroids
 M. tuberculosis , T. pallidum, M. leprae involved in chronic
disease
 Nocardia asteroids can cause granulomatous disease
o Viruses
 HSV, VZV, CMV
 HSV, VZV, CMV may be involved in necrotizing disease
o Fungi
 Histoplasma sp., Aspergillus sp., Candida sp.
 These all cause granulomatous disease of the uveal tract.
Infections of the retina (retinitis)
o Pneumocystis carinii invades retina during systemic disease
o Viruses
 CMV, HSV, VZV
 In US, HSV infection leading cause of blindness
 Both HSV I and II
 Newborn- acute necrotizing retinitis result of acquiring
virus passing through infected birth canal
 Adult- acquire from recurrent episodes of viral keratitis
 Treatment with acyclovir, ganciclovir, foscarnet
o Parasites




T. gondii, Cysticercus, Toxocara sp., Loa loa
T. gondii has predilection for ocular tissues
Cysticercus cellulosae, Toxocara sp. found in 10-13% of all
intraocular infections.
Diagnostic Principles
o Sufficient material must be collected from the infected site with minimal
contamination from adjacent fluids, secretions, structures
o Appropriate collection device, transport medium, culture media must be
used.
o Material should be collected early in course of infection and in absence of
recent antimicrobial treatment
o Culture and Transport Media for Ocular Specimens
o Guide to Specimen Collection for Common Ocular Infections

Diagnostic Techniques
o Nucleic acid hybridizations
 Can visualize hybridization between possible test sequences and
specific probes
 Synthesis of DNA (oligonucleotides)
 Can chemically synthesize small pieces of DNA to
whatever specifications needed
o Polymerase Chain Reaction (PCR)
 Method to rapidly amplify any region of DNA millions of times
 Important for diagnostics, preparatives, etc.
 Inventor (Kary Mullis) received Nobel Prize in Chemistry
 Patent rights have been sold to Roche for $300 million.
Bacterial Infections of Childhood and Adolescence
(Each of these infections are preventable by routine childhood vaccinations)

DPT Vaccine
o Diptheria- Corynebacterium diptheriae
 Formation of a pseudomembrane in the posterior pharynx which
can be aspirated and cause death from asphyxiation.
 Produces a potent toxin that inhibits cellular protein synthesis and
causes cell death. Anti-toxin must be given in addition to
antibiotics.
 Also see conjunctivitis, bull neck, severe myocarditis.
 All vaccines are contraindicated.
o Pertussis- Bordetella pertussis (whooping cough)
 Commonly known as whooping cough, vaccination has markedly
reduced rates in the US, although outbreaks still occur, but are rare.
 Worldwide, there are 50 million cases annually, with 1 million
death.
 Most characteristic clinical feature is paroxysms of coughing, with
the characteristic “whoop”
o Tetanus
Common Outpatient Infections
 Acute suppurative otitis media
o Middle ear infection
o Vs. swimmer’s ear which is an external otitis.
o Fluid behind the tympanic membrane with bacteria.
o AKA
 Acute purulent otitis media
 Acute otitis media
o Other entities
 Myringitis- tympanic membrane inflamed
 Secretory otitis media- only fluid trapped (no bacteria)
 Chronic suppurative otitis media- not rapid onset. Pus behind the
eardrum.
o Clinical presentation and diagnosis
 Viral prodrome
 Ear pain- estauchian tube filled with mucous and fluid collects in
middle ear.
 Fever
 Hearing loss- due to fluid
 Pulling not diagnostic
 Referred sources of ear pain (sinus throat, pharynx)
o Diagnosis
 With otoscope
 Normal- can see through the membrane
 A cone of light reflection is seen in the normal ear.
 Abnormal
 Cannot see the bones due to the membrane being red and
swollen.




Cone of light pushed forward.
Painful.
Sometimes pus can be seen.
o Pathogens
 Strep pneumoniae- 30-40%
 Haemophilus influenzae- 20-30%
 Moraxella (Branhamella) catarrhalis- 12-20%
 Beta lactamase production (breaks the Abs like PCN)
 Chronic suppurative OM- Pseudomonas, Enterobacter, Staph,
anaerobes
o Treatment
 First line
 Amox, erythro, TMP-SMZ
 Second line
 Augmentin, extended macrolides, 2nd and 3rd generation
cephalosporins
 Duration- 7-10 days
 Many kids improve without antibiotics. Just treat the pain and
fever.
Acute sinusitis
o Pathogens- same as OM
o They obstruct the mucous outflow.
o Clinical presentation and diagnosis
URI/ Cold
Acute Sinusitis
5-10 days duration
>10 days
Watery, thin rhinorrhea
Serous mucoid
Nonspecific cough
Cough worse at night
Normal breathing
Malodorous breath
Myalgias, HA
Sinus HA (over frontal or
maxillary sinuses)
Min to no facial pain
Facial pain present with typical
radiation
Antibiotics do not help
Cold is basically gone
since it is a virus
No systemic aches
 Pain
 Location
 Provocation
 Radiation
 Nasal congestion
 Purulence- 80% Sn, 52% Sp (green)
 Fever
 Symptom onset 3-10 days into cold = “Double Sickening”
o Treatment
 Amoxicillin or TMP-SMZ (or Bactrum)



Augmentin, 2nd Gen Ceph, 2nd Macrolide
Adjunctive treatment
 Decongestants, nasal steroids, and humidification can all be
used to loosen up the mucous and open the airways.
o Clinical course
 10-14 day treatment
 no resolution- 2nd line tx 3 weeks with nasal steroid
 When to obtain
 Rhinoscopy (look for polyps)- these block mucous
o Symptoms return <4 weeks, no improvement after
2nd Ab course.
 CT (look for opacification, air/fluid level)
o Multiple previous episodes.
UTIs
o Clinical presentation and diagnosis
 Questions to ask
 Is dysuria from urinary system?
 If so, is it an infection?
 If a UTI, is it upper or lower tract?
 Is this an isolated or recurrent episode
 Any special concerns about this patient?
 Differential diagnosis of dysuria (painful urination)
 Lower tract infection (bladder)
o This is the most common
 Vaginitis (yeat infection)
o Common
 Upper tract infection- less common
 Urethritis- less common
o Red flags for complicated infections
 Male gender
 Extremes of age (young or old)
 Symptoms present for more than 7 days
 Immunosuppression from HIV, DM, or cortisone
 Hx of pyelonephritis
 Pregnancy
 Fever, flank (back) pain  kidney
 DM
o Pathogens
 E. Coli
 80-90% of outpatient UTIs.
 Less common
 Proteus, Klebsiella, Enterobacter
o Treatment
 TMP-SMX, Bactrin/Septra
 Fluoroquinolones
 Macrodantin
 Probably not amoxicillin, because it is E. Coli resistant
o Clinical course
 3 day treatment fro uncomplicated lower UTI
 symptomatic improvement 3 days
 warn regarding complications
 fluids, cranberry juice