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Bacterial Diseases
Rickettsias, Chlamydias, Spirochetes and Vibrios
Bacterial Diseases Classified by:
 Airborne
 Foodborne
 Waterborne
 Soilborne
 Arthropodborne
 Physical Contact
Or by…..
Physiological properties:
Hydrogen peroxide
hydrogen peroxide
Breakdown peroxidase (by-products that cause
tissue damage)
Or, by……..
 Gram-positive
 Gram-negative
 Rickettsias, Chlamydias, Spirochetes and
Gram-positive bacteria
Staphylococcus aureus
 Capsule!
 grows in large, round,
opaque colonies
 optimum temperature
 facultative anaerobe
 withstands high salt,
extremes in pH, & high
 produces many
virulence factors
 Coagulase
coagulates plasma and
produced by 97% of
human isolates
 Hyaluronidase
promotes invasion
 Staphylokinase
digests blood clots
 Dnase
digests DNA
 Lipases
helps bacteria colonize
oily skin
 Penicillinase
inactivates penicillin
Enzymes of S. aureus
Toxins of S. aureus
lyse RBCs
damages cell membranes
act in the gastrointestinal tract
exfoliative toxin
separates epidermal layers
toxic shock syndrome toxin (TSST)
Epidemiology and Pathogenesis
 Present in most environments frequented by
 Readily isolated from fomites
 Carriage rate for healthy adults is 20-60%
mostly in anterior nares, skin, nasopharynx, intestine
 Predisposition to infection include:
poor hygiene and nutrition, tissue injury, preexisting
primary infection, diabetes, immunodeficiency
 Increase in community acquired methicillin
Staphylococcal Disease - 1
 Localized cutaneous infections – invade skin through
wounds, follicles, or glands
 folliculitis
 superficial inflammation of hair follicle
 usually resolved with no complications but can progress
 furuncle
 Boil
 inflammation of hair follicle or sebaceous gland progresses into abscess
or pustule
 carbuncle
 larger and deeper lesion created by aggregation and interconnection of
a cluster of furuncles
 impetigo
 bubble-like swellings that can break and peel away
 most common in newborns
Staphylococcal Disease - 2
 Systemic infections
 infection is established
in the metaphysis
 abscess forms
 primary origin is
bacteria from another
infected site or
medical devices
 endocarditis possible
Staphylococcal Disease - 3
 Toxigenic disease
food intoxication
 ingestion of heat stable
 gastrointestinal distress
staphylococcal scalded skin
 toxin induces bright red flush,
blisters, then desquamation of
the epidermis
 toxic shock syndrome
 toxemia leading to shock and
organ failure
Other Staphylococci
 S. epidermidis
lives on skin & mucous
endocarditis, bacteremia, UTI
 S. hominis
lives around apocrine sweat
 S. capitis
live on scalp, face, external
 S. saprophyticus
infrequently lives on skin,
intestine, vagina; UTI
 Gram-positive spherical/ovoid
cocci arranged in long chains
 Non-spore-forming, nonmotile
 Can form capsules & slime layers
 Facultative anaerobes
 Sensitive to drying, heat & disinfectants
 25 species
 Lancefield classification
system based on cell wall Ag
17 groups (A,B,C,….)
 Another classification system
is based on hemolysis
 b-hemolysis
 A,B,C,G & some D strains
 a –hemolysis
 S. pneumoniae & others
collectively called viridans
 γ-hemolysis
 Enterococcus faecalis
 does not induce hemolysis
Skin infections
 Impetigo (pyoderma)
 superficial lesions that break and
form highly contagious crust
 often occurs in epidemics in
school children
 associated with insect bites, poor
hygiene, and crowded living
 Erysipelas
 pathogen enters through a break in
the skin
 eventually spreads to the dermis
and subcutaneous tissues
 can remain superficial or become
Throat infections
 Streptococcal pharyngitis
 strep throat
b-hemolytic S. pyogenes
 Most serious
streptococcal pathogen
 Inhabits throat,
nasopharynx, occasionally
 Produces Ccarbohydrates, M-protein
(fimbrae), streptokinase,
hyaluronidase, DNase,
S. pyogenes
Produces toxins
Humans only reservoir
 contact, droplets, food, fomites
 Skin infections
 pyoderma, impetigo,
 Systemic infections
 strep throat, pharyngitis,
scarlet fever
S. pyogenes
 Causes streptococcal
Strep throat
enters the upper
respiratory tract through
respiratory droplets
 Some patients with
strep throat may
develop scarlet fever
exhibiting a rash caused
by erythrogenic exotoxins
S. pyogenes
 Rheumatic fever
 serious complication
affecting the joints and
 causes permanent heart
damage called rheumatic
heart disease
 Acute glomerulonephritus
 rare inflammatory
response to M proteins
 may lead to renal damage
Group B: S. agalactiae
 Regularly resides in human vagina, pharynx &
large intestine
 wound and skin infections & endocarditis in
debilitated people
 can be transferred to infant during delivery &
cause severe infection
Most prevalent cause of neonatal pneumonia,
sepsis, & meningitis
Targets infants without Ab, and mothers that do not
provide passive immunity
Pregnant women should be screened & treated
“Typical” Pneumonia Can Be Caused by
Several Bacteria:
 80% of “typical”
pneumonia cases are
caused by
 Others:
Haemophilus influenzae
Staphylococcus aureus
Klebsiella pneumoniae
Streptococcus pneumoniae
 Small, lancet-shaped cells
arranged in pairs and short
 Culture requires blood or
chocolate agar
 Growth improved by 5-10%
 Lack catalase &
 cultures die in O2
S. pneumoniae
 All pathogenic strains
form large capsules
major virulence factor
 Vaccine available for
high risk people
S. Pneumoniae Epidemiology
5-50% of all people carry it as normal flora
in pharynx
Does not survive long outside of its habitat
Pneumonia occurs when cells are
aspirated into the lungs of susceptible
Pneumococci multiply
induce inflammatory response
Traditionally treated with penicillin G or V
Increased drug resistance
Cultivation and Diagnosis
Gram stain of specimen
presumptive identification
α hemolytic
Quellung test or capsular swelling
motile rods
mostly saprobic
 primary habitat is soil
 versatile in degrading complex macromolecules
 source of antibiotics
 2 species of medical importance
Bacillus anthracis
Bacillus cereus
Bacillus anthracis
 facultative
 large, block shaped
 central spores
develop under all
conditions except in the
living body
 virulence factors
capsule & exotoxins
Bacillus anthracis
 3 types of anthrax
 Cutaneous
 spores enter through skin,
black sore
 least dangerous
 Pulmonary
 inhalation of spores
 Gastrointestinal
 ingested spores
 treated with penicillin or
Bacillus cereus
 common airborne &
 grows in foods, spores
survive cooking & reheating
 ingestion of toxin-containing
causes nausea,
vomiting, abdominal
cramps & diarrhea
24 hour duration
 no treatment
 spores abundant in the
 gram-positive
 spore-forming rods
 Anaerobic
 120 species
 oval or spherical spores produced only under
anaerobic conditions
 cause wound & tissue infections and food
C. difficile
C. botulinum
C. perfringens
C. tetanis
Clostridium difficile-Associated Disease
 Normal resident of colon, in low
 Causes antibiotic-associated
 relatively non-invasive
 treatment with broad-spectrum
antibiotics kills the other bacteria
 allowing C. difficile to
 Produces enterotoxins that
damage intestines
 Major cause of diarrhea in
 Increasingly more common in
community acquired diarrhea
Clostridium botulinum
 Anaerobic, endospore-forming, Gram-positive
 Common in soil and water
 Botulism results when the endopsores germinate
and produce botulism toxins
Clostridium botulinum
Causes 3 diseases
1. food poisoning
spores are in soil, may contaminate vegetables
improper canning does not kill spores & they germinate in
the can producing botulinum toxin
 toxin causes paralysis by preventing release of
2. infant botulism
caused by ingested spores that germinate & release toxin
3. wound botulism
spores enter wound & cause food poisoning symptoms
Clostridium botulinum
Symptoms are diagnostic
Administer neutralizing antibodies against
botulism toxin
Administer antimicrobial drugs in infant
botulism cases
Proper canning of food
Infants under 1 year should not consume
Clostridium perfringens
Mass of body tissue dies (necrosis)
Usually occurs when blood flow ceases to a
part of the body
Types :
Gas gangrene (myonecrosis)
caused when spores enter the body through a
severe open wound
Dry gangrene
Wet gangrene
Clostridium perfringens
 Vegetative cells ferment
muscle carbohydrates and
decompose muscle proteins
 Large amounts of gas
accumulate under the skin
 causing a crackling sound
 a-toxin damages and lyses
blood cells
 Treatment involves:
tissue debridement
exposure in a hyperbaric
oxygen chamber
Clostridium tetani
Causes hyperactive muscle contractions
Spores can enter the body through a wound
produce toxins
• Tetanospasmin inhibits compounds needed to inhibit
muscle contraction
Clostridium tetani
 Symptoms of tetanus include:
Trismus (lockjaw)
 involves spasms of the jaw muscle and clenching of the
 involves muscle spasms that cause an arching of the back
Spasmodic inhalation and seizures in the diaphragm and
rib cage
 reduces ventilation
 Sedatives, muscle relaxants, and penicillin are
used in treatment
 Tetanus toxoid is used in vaccination
Listeria monocytogenes
non-spore-forming gram-positive
1-4 flagella
no capsules
resistant to cold, heat, salt, pH extremes &
primary reservoir is soil & water
can contaminate foods & grow during
Listeria monocytogenes
 Listerosis
 immunocompromised patients,
fetuses & neonates
 affects brain & meninges
20% death rate
 ampicillin & trimethoprimsulfamethoxazole
 Prevention
pasteurization & cooking
 M. pneumoniae
 primary atypical
 Walking pneumonia
 pathogen slowly spreads
over interior respiratory
 causes fever, chest pain
and sore throat
Corynbacterium diptheriae
gram-positive irregular bacilli
2 stages of disease:
1. Local infection
–upper respiratory tract inflammation
– sore throat, nausea, vomiting,
swollen lymph nodes,
pseudomembrane formation
can cause asphyxiation
2. Diptherotoxin production and
 target organs primarily heart and
Epidemiology and Pathology
 Reservoir of healthy
potential for diphtheria
is always present
 Most cases occur in nonimmunized children living
in crowded, unsanitary
 Acquired via respiratory
droplets from carriers or
actively infected
Corynbacterium diptheriae
Diagnostic methods
Pseudomembrane and swelling indicative
Conditions, history
Serological assay
Penicillin or erythromycin
Prevented by toxoid vaccine series and
Mycobacterium Genus
 gram-positive irregular bacilli
 acid-fast staining
 strict aerobes
 produce catalase
 possess mycolic acids & a unique type of
 do not form capsules, flagella or spores
 grow slowly
 2 medically important:
Mycobacterium tuberculosis
Mycobacterium leprae
Mycobacterium tuberculosis
 contain complex waxes
& cord factor
prevent destruction by
lysosomes of
 transmitted by airborne
respiratory droplets
 only 5% infected people
develop clinical disease
Primary TB
 infectious dose 10 cells
 phagocytosed by
alveolar macrophages
multiply intracellularly
 after 3-4 weeks
immune system
attacks, forming
granulomas consisting
of a central core
containing bacilli
surrounded by WBCs
Secondary TB
reactivation of bacilli
tubercles expand & drain into the bronchial
tubes & upper respiratory tract
gradually patient experiences more severe
violent coughing, greenish or bloody sputum,
fever, anorexia, weight loss, fatigue
untreated 60% mortality rate
Extrapulmonary TB
during secondary TB, bacilli disseminate
to regional lymph nodes, kidneys, long
bones, genital tract, brain, meninges
these complications are grave
1. in vivo or tuberculin
2. X rays
3. direct identification
of acid-fast bacilli in
4. cultural isolation
and biochemical
Treatment of TB
6-24 months of at least 2 drugs from a list
of 11
one pill regimen called Rifater (isoniazid,
rifampin, pyrazinamide)
vaccine based on attenuated bacilli
Calmet-Guerin strain of M. bovis used in
other countries
Mycobacterium leprae
 Hansen’s bacillus
 strict parasite
 slowest growing of all species
 multiplies within host cells in large packets called
 causes leprosy
chronic disease that begins in the skin & mucous
membranes & progresses into nerves
Leprosy (Hansen’s Disease)
 spread through direct inoculation
from leprotics
 2 forms
 superficial infection without skin
 damages nerves and causes loss of
pain perception
 deeply nodular infection
 causes severe disfigurement of the
face & extremities
 Combination of
examination of
lesions, and patient
 Detection of acid-fast
bacilli in skin lesions,
nasal discharges,
and tissue samples
Treatment and Prevention
 Treatment by longterm combined
 Prevention requires
constant surveillance
of high risk
 WHO sponsoring a
trial vaccine
Gram-negative Cocci and Bacilli
Bacterial Meningitis
 meninges of brain and
spinal cord
cross the blood-brain
 can be caused by
several bacterial
Neisseria meningitides
Haemophilus influenzae
Gram-negative diplococci
none develop flagella or spores
capsules on pathogens
Strict parasites
 do not survive long outside of the host
 Residents of mucous membranes of warm-blooded
 Aerobic or microaerophilic
 Pathogenic species require enriched complex media and
 2 primary human pathogens
 Neisseria gonorrhoeae
 Neisseria meningitidis
Neisseria meningitidis
 Virulence factors
capsule, pili, IgA protease
 12 strains
serotypes A, B, C, cause most cases
 Disease begins when bacteria enter bloodstream,
pass into cranial circulation, multiply in meninges
very rapid onset
endotoxin causes hemorrhage and shock
can be fatal
 Treated with penicillin, chloramphenicol
 Vaccines exist for group A and C
Neisseria gonorrhoeae
 Causes gonorrhea
 Virulence factors
pili, other surface molecules, IgA protease
 Strictly a human infection
 In top 5 STDs
 Infectious dose 100-1,000
 Does not survive more than 1-2 hours on
 Infection is asymptomatic in 10% of males and
50% of females
 Males
urethritis, yellowish
discharge, scarring &
Extragenital infections
 anal, pharygeal,
septicemia, arthritis
 Females
vaginitis, urethritis,
salpingitis (PID) mixed
anaerobic abdominal
common cause of
sterility & ectopic tubal
Gonorrhea in Newborns
 Infected as they pass
through birth canal
 Eye inflammation,
 Prevented by
prophylaxis after birth
Diagnosis and Control
Gram stain
20-30% of new cases
are penicillinaseproducing PPNG or
tetracycline resistant
Recurrent infections
can occur
Reportable infectious
Enterobacteriaceae Family
 Enterics
 gram-negative bacteria
 many members inhabit soil,
water, & decaying matter
 cause diarrhea through
 divided into coliforms (lactose
fermenters) and non-coliforms
(non lactose fermenters)
Antigens and virulence factors of
typical enteric bacteria
Testing of Enterics
miniaturized, multichambered tube
inoculating rod pulled through length of tube
carries an inoculum to all chambers
Coliform Organisms and Diseases:
Escherichia coli
most common aerobic & non-fastidious
bacterium in gut
@ 150 strains
Most not infectious
Escherichia coli
 enterotoxigenic E. coli
causes severe diarrhea due to heat-labile
heat-stable toxin
stimulate secretion & fluid loss
also has fimbrae
toxin &
 enteroinvasive E. coli
causes inflammatory disease of the large intestine
 enteropathogenic E. coli
linked to wasting from infantile diarrhea
 Enterohemorrhagic E. coli
Newest strain
Can permanently damage kidney
Escherichia coli
pathogenic strains frequent agents of
infantile diarrhea
greatest cause of mortality among babies
causes ~70% of traveler’s diarrhea
causes 50-80% UTI
indicator of fecal contamination in water
Other Coliforms
 Serratia marcescens
produces a red pigment
causes pneumonia,
burn & wound
infections, septicemia &
 Klebsiella
 Citrobacter
opportunistic UTIs &
 S. enteritidis
 1,700 serotypes
 salmonellosis
 zoonotic
 gastroenteritis 2-5 days
Typhoid Fever
 caused by Salmonella enterica
serotype Typhi
 (S. typhi)
 typhoid fever
 ingested bacilli adhere to small
 cause invasive diarrhea that leads
to septicemia
 S. Typhi is transmitted by the
five Fs:
 shigellosis
 incapacitating dysentery
 S. dysenteriae, S. sonnei,
S. flexneri & S. boydii
 produce H2S or urease
 Nonmotile
 nonencapsulated
 invades villus of large intestine
can perforate intestine or invade blood
 enters Peyer’s patches & instigates inflammatory
 endotoxin & exotoxins
 treatment
 fluid replacement & ciprofloxacin & sulfa-trimethoprim
Yersinia pestis
tiny, gram-negative rod
unusual bipolar staining & capsules
virulence factors
capsular & envelope proteins protect against
phagocytosis & foster intracellular growth
Yersinia pestis
 sylvatic plague
humans develop plague through contact with wild
 urban plague
domestic or semidomestic animals or infected humans
 found in 200 species of mammals
rodents harbor the organism but do not develop the
 flea vectors
bacteria replicates in gut, coagulase causes blood
clotting that blocks the esophagus
flea becomes ravenous
Pathology of Plague
 bubonic
 bacillus multiplies in flea bite, enters
lymph, causes necrosis & swelling in
groin or axilla
 bubo
 septicemic
 progression to massive bacterial growth
 virulence factors cause intravascular
coagulation subcutaneous hemorrhage
& purpura
 black plague
 pneumonic
 infection localized to lungs, highly
 fatal without treatment
 Treatment
tetracycline or
 Killed or attenuated
Bordetella pertussis
 aerobic coccobacillus
 causes pertussis or whooping cough
communicable childhood affliction
 acute respiratory syndrome
 often severe, life-threatening complications in
 reservoir
apparently healthy carriers
 transmission by direct contact or inhalation of
Bordetella pertussis
virulence factors
receptors that recognize & bind to ciliated
respiratory epithelial cells
toxins that destroy & dislodge ciliated cells
DTaP vaccine
acellular vaccine contains toxoid & other Ags
small gram-negative bacilli
single polar flagellum
highly versatile metabolism
Pseudomonas aeruginosa
intestinal resident in 10% normal people
resistant to soaps, dyes, quaternary
ammonium disinfectants, drugs, drying
Use aerobic respiration
do not ferment carbohydrates
Pseudomonas aeruginosa
 common cause of nosocomial infections in hosts
with burns, neoplastic disease, cystic fibrosis
 complications include pneumonia, UTI,
abscesses, otitis, & corneal disease
 grapelike odor
 greenish-blue pigment (pyocyanin)
 multidrug resistant
Francisella tularensis
 causes tularemia
zoonotic disease of mammals (particularly rabbits)
endemic to the northern hemisphere
 Aerobic bacilli
 transmitted by contact with infected animals,
water & dust or bites by vectors
 headache, backache, fever, chills, malaise &
 intracellular persistence can lead to relapse
 30% death rate in systemic & pulmonic forms
gentamicin or tetracycline
“Atypical” Pneumonia Can Be Caused by
a Diverse Group of Bacterial Species
Mycoplasma pneumoniae
Legionella pneumophila
Coxiella burnetii
Chlamydia pneumoniae
Chlamydia psittaci
Legionella pneumophila
 “Legionellosis”, Legionaires
 Motile aerobic bacilli
 widely distributed in water
 live in close association with
 prevalent in males over 50
 nosocomial disease in elderly
 fever, cough, diarrhea,
abdominal pain, pneumonia
 fatality rate of 3-30%
 azithromycin
Rickettsias, Chlamydias,
Spirochetes and Vibrios
 obligate intracellular parasites
 gram-negative cell wall
 among the smallest bacteria
 nonmotile pleomorphic rods or coccobacilli
 ticks, fleas & louse are involved in their life cycle
 bacteria enter endothelial cells & cause necrosis
of the vascular lining
 treat with tetracycline & chloramphenicol
4 Types of Rickettsioses
Rocky Mountain spotted fever
R. rickettsii
zoonosis carried by dog ticks & wood ticks
most cases on eastern seaboard
distinct spotted rash
 obligate intracellular
 small gram-negative
cell wall
 alternate between 2
elementary body
 small metabolically
inactive, extracellular,
infectious form
reticulate body
 grows within host cell
Chlamydia trachomatis
 1. trachoma
 attacks the mucous membranes of the
eyes, genitourinary tract & lungs
 ocular trachoma
• severe infection, deforms eyelid &
cornea, may cause blindness
 inclusion conjunctivitis
• occurs as babies pass through birth
• prevented by prophylaxis
 2. STD
 urethritis, cervicitis, scarring
 lymphogranuloma venereum
 disfiguring disease of the external
genitalia & pelvic lymphatics
Spreading to the fallopian
tubes can cause salpingitis
Left untreated can cause
pelvic inflammatory disease
Increases the danger of
infertility or ectopic
Chlamydia can also occur in
the pharynx or anus
Males complain of painful
urination and watery discharge
cause infertility in males
Gram-negative spirochetes
live in the oral cavity, intestinal tract, &
perigenital regions of humans & animals
pathogens are strict parasites
Treponema pallidum
 human is the natural host
 extremely fastidious &
cannot survive long outside
of the host
 causes syphilis
 ID = 50 cells
Pathogenesis and Host Response
 Spirochete binds to epithelium, multiplies, and
penetrates capillaries.
 Moves into circulation and multiplies
 Untreated marked by stages
 Spirochete appears in lesions and blood during
first 2 stages
Stages of Syphilis
 Primary syphilis
 appearance of hard
chancre at site of
 chancre heals
 Secondary syphilis
 fever, headache, sore
throat, red or brown rash
on skin, palms and soles
 rash disappears
Stages of Syphilis
 Tertiary syphilis
 about 30% of infections enter
in tertiary stage
 can last for 20 years or longer
 neural, cardiovascular
symptoms, gummas develop
 Congenital syphilis
 nasal discharge, skin
eruptions, bone deformation,
nervous system abnormalities
Gram-negative spirochetes
transmitted by arthropod vector
B. hermsii
relapsing fever
B. burgdorferi
Lyme disease
B. hermsii - Relapsing Fever
 mammalian reservoirs
squirrels, chipmunks, wild rodents
 tick-borne
 after 2-15-day incubation, patients have high
fever, shaking, chills, headache, & fatigue
 Nausea, vomiting, muscle aches, abdominal
extensive damage to liver, spleen, heart, kidneys, &
cranial nerves
 parasite changes & immune system tries to
control it
recurrent relapses
 tetracycline
B. burgdorferi - Lyme Disease
 transmitted by ticks
 complex 2-year cycle
involving mice & deer
 nonfatal, slowly
progressive syndrome
that mimics
neuromuscular &
rheumatoid conditions
B. burgdorferi - Lyme Disease
 Symptoms:
 70% get bull’s eye rash
 fever, headache, stiff
neck, & dizziness
 if untreated can progress to
cardiac & neurological
symptoms, polyarthritis
 tetracycline, amoxicillin
 vaccine for dogs, human
vaccine discontinued
 insect repellant containing
Vibrio cholera
 Cholera
 Curviform gramnegative
 top 7 causes of
morbidity & mortality
 ingested with food or
 infectious dose 108
Vibrio cholera
infects surface of small intestine,
cholera toxin causes electrolyte & water
loss through:
 secretory diarrhea, resulting dehydration leads
to muscle, circulatory, & neurological symptoms
oral rehydration, tetracycline
Campylobacter jejuni
 important cause of bacterial
 transmitted by beverages &
 Curviform gram-negative
 reach mucosa at the last
segment of small intestine
near colon
adhere, burrow through
mucus and multiply
 symptoms of headache,
fever, abdominal pain,
bloody or watery diarrhea
Helicobacter pylori
Curviform gram-negative
discovered in 1979 in stomach biopsied
causes 90% of stomach & duodenal ulcers
people with type O blood have a 1.5-2X
higher rate of ulcers
Same receptor in common
produces large amounts of urease
© P. Hawtin/Photo Researchers, Inc.
 The bacteria produce
urease, which in turn
produces ammonia
neutralizes acid in
that area of the
allows the
bacteria to survive
 The ammonia, and
an H. pylori cytotoxin
destroy mucoussecreting cells
creates a sore
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