Download microbiology – test 3 material

MICROBIOLOGY – TEST 3 MATERIAL
PATHOGENS IN A SYSTEMS APPROACH
Antimicrobial drugs:
 Narrow spectrum – mostly effective against Gram + bacteria…example penicillin
 Broad spectrum – effective against Gram + and Gram – bacteria…example antibiotics.
Overgrowth – phenomenon seen when antibiotics kill off pathogens and our normal flora, allowing for
overgrowth of other normal flora such as yeast.
Example…woman takes antibiotics for 10 days and the next thing they know is that they have a
yeast infection b/c the normal flora that kept the yeast in check is now gone b/c of the antibiotics.
Super Infection – pathogen that develops tolerance to many drugs and antibiotics.
Example…people are given antibiotics for UTI’s that are supposed to be taken 3-x day for 10
days. But before the 10 days are up, symptoms disappear and the remainder of the dose is not taken. A
few days later the symptoms return so the rest of the antibiotic is taken. What happens is the pathogen
builds up a tolerance to the antibiotics b/c the dose was not taken for the minimum 10 days. Soon, no
amount of antibiotics will work to eliminate the pathogen.
Antibiotics work in 2 ways:
1. Bactericidal – kills the bacteria
2. Bacteriaostatic – stops the bacteria from reproducing (die in about ½ hour)
Categories of Antibiotic Activity:
 Inhibition of Cell Wall
- Bacterial cell walls are made of peptidoglycans; antibiotics sometimes inhibit this cell wall
building block. Examples include penicillin and amoxicillin.
- These antibiotics target bacteria that are alive and growing.
- Our cells don’t have peptidoglycans, so penicillin is not toxic to our cells.

Inhibition of Protein Synthesis
- Prokaryotes and eukaryotes synthesize proteins (good targets for antibiotics)
- Antibiotics such as erythromycin, streptomycin and tetracycline inhibit protein synthesis
(broad spectrum).
- Erythromycin is not a broad-spectrum antibiotic b/c it’s not effective against Gram – bacteria.
- Tetracycline works by interfering w/ the attachment of amino acids to a polypeptide chain
such as tRNA. It doesn’t affect this process in humans b/c it doesn’t cross our cell
membranes very easily.
i. Exception to this is if we have chlamydia or rickettsias in our cells; large doses of
tetracycline can then enter our cells.
- Aminoglycosides also interfere w/ protein synthesis by affecting mRNA; inability to read it
correctly. Other examples of drugs that interfere w/ mRNA are streptomycin and gentamycin.

Injury to Plasma Membrane
- Polymyxin B alters permeability of plasma membrane.
- Antifungal drugs such as Amphoterician B affect the sterols in the plasma membranes of
fungus. Our membranes don’t have sterols in them b/c they are stored as cholesterol in our
cells.
- Large % of AIDS patients die of fungal infections and they are usually on Amphoterician B.
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Inhibition of Essential Metabolites
- Sulfa drugs compete w/ enzymes needed for bacterial growth. They work as bacteriostatic
drugs by not allowing PABA to be converted into folic acid in the bacteria.
- Kidneys stones are usually caused by increased intake and buildup of sulfa drugs.
--STEVE’S NOTES-BEST DAMN NOTES AROUND
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Antiviral drugs
- These are usually nucleotide analogs (examples Acyclovir and AZT)
- AZT used in AIDS treatment works by blocking syntheses of DNA of HIV virus by blocking
reverse transcriptinase enzyme. Side effects of AZT is anemia; need transfusions regularly
which then puts you at greater risk of coming in contact w/ AIDS virus again.
- Protease inhibitors – These affect/block AIDS virus ability to cut portions of protein into
smaller portions to make more viruses.
INFECTIONS OF THE SKIN AND EYES
Bacterial infections are most common (staph and strep)
1.
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2.
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3.
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4.
Staph – Gram + cocci – categorized by whether it produces coagulase enzyme or not.
- Staph epidermidis – no coagulase enzyme (normal flora)
- Staph aureus – has coagulase enzyme (pathogen)
- Small % of people are carriers of staph aureus w/o symptoms. Found in nasal pharynx and
throat. Those most susceptible to staph are infants and immune suppressed people.
Examples of infections caused by staph
 Folliculitis – infection and inflammation of hair follicles (usually in children). Looks like
goose bumps but isolated to follicle.
 Sty – infection/inflammation of hair follicles of eye (eyelashes)
 Impetigo – infection seen in kids w/ boil-like vesicles that burst and crust over on the skin;
could lead to infection going to deeper tissue and blood.
 Toxemia/Septicemia – bacteria growing in bloodstream and releasing toxins.
 Scalded Skin Syndrome – skin appears scalded (appears around mouth and nose) skin and
blood is loaded w/ bacteria and toxins are being released. Skin just melts off leaving open
and puss-filled wound. Kids can die if not treated heavily for this.
 Toxic Shock Syndrome – skin looks like severe sunburn and they lose fluids through skin,
diarrhea and have fever. 20-25% mortality rate.
Strep – Gram + cocci (3 kinds …alpha and gamma are non-pathogenic but beta kind is pathogenic)
- Beta hemolytic strep are categorized by their M-proteins (80 different kinds)
- M-proteins have anti-phagocytizing properties and these contribute to pathogenicity.
Examples of infections caused by strep
 Impetigo, strep throat, scarlet fever and erysipelas (St. Anthony’s fire)
- Strep pyogens is the main culprit. Pyogens means heat is involved along with pus.
Pseudomonas – Gram – rod found in soil. These bacteria grow well in alkaline environments.
- These are opportunistic pathogens in that they wait for our immune system to be weakened.
- P. Aeruginosa is most common infectious agent in burns/burn victims. Grows in warm, moist
and oxygenated environment. Grows w/ a yellow/green pigment. Seen mainly in lungs and
when you spit up greenish phlegm you know you have a pseudomonas infection. It smells
musty. This bacteria kills cystic fibrosis and lung cancer patients.
Examples of infections caused by pseudomonas
 P. Dermatitis – seen in hot tubs and saunas and weight room showers. Water should be
chlorinated and acidic to combat these bacteria. Lots of people in a hot tub turn the water
alkaline.
 Swimmer’s Ear – seen from swimming in contaminated lake water. If in a swimming pool,
probably not pseudomonas b/c of chlorine.
Acne – most common skin disorder/infection
- Transient acne comes and goes but cystic acne is always there w/ deep pustules and sores.
- Acne is a manifestation of bacteria growing in our sebaceous gland secretions. (Gram +)
- OTC drugs such as benzyl peroxide target Gram + bacteria. Acutane (derivative of vit. A)
inhibits sebum production so there is nothing for the bacteria to eat. Don’t take if pregnant!!
- Know that estrogen decreases sebum production and testosterone increases sebum production,
that’s why women don’t get as much acne as men do.
--STEVE’S NOTES-BEST DAMN NOTES AROUND
5.
Fifth Disease – (aka erythema infectiosum)
- Years ago, it was on a list of contagious diseases at the #5 slot.
- Appears w/ a “slapped face” appearance.
- Skin viral disease, no complications, goes away on its own.
FUNGAL DISEASES (mycoses)
These tend to invade warm, moist skin areas.
1. Cutaneous Mycoses (dermatomycoses)
- This type of fungus affects skin, hair, nails…most common cause is ringworm (not a worm-a
fungus).
 Tinea Capitis – ringworm on head
 Tinea Pedis – ringworm on feet (athlete’s foot)
2.
Subcutaneous Mycoses
- This type of fungus is more serious b/c it is closer to internal environment of our bodies.
- Usually caused from a fungus in the soil by penetration of our skin.
 Sporotrichosis – (dimorphic; can be a yeast or mold) most common subcutaneous
mycoses and is easy to treat.
 Candidiasis – caused by candidia yeast. This yeast affects mucous membranes (GI tract,
vagina, mouth…) If seen in mouth it’s called thrush. Main causes are overuse of
antibiotics and being immune compromised. Nystatin drug and Difucan pills are the
drugs of choice for yeast infections.
PARASITIC DISEASES
1. Scabies – parasites bore through outer layer of skin and lay eggs. Eggs hatch and continue the process.
- OTC solutions work to get rid of scabies.
DISEASES OF THE EYE
1. Conjunctivitis – generic term for inflammation of conjunctival lining.
- Increase in conjunctivitis is due to contact lenses.
2.
Neonatal Gonorrhea (bacterial disease)
- Baby gets this from the vaginal wall during birth from the mother.
- Causes ulcerations to neonate’s eyes (cornea) and can lead to blindness.
- Doctors used to give silver nitrate to every child that was born.
3.
Inclusion Conjunctivitis
- This is caused by clamydia and causes ulcerations on cornea and can lead to blindness.
- Tetracycline is used to deal w/ this.
4.
Herpetic Kerratitis
- This is herpes in the eyes. Make sure you wash your hands after applying cream.
VIRAL SKIN DISEASES
1. Warts (papillomas) – caused by about 50 viruses and are almost always benign.
2.
Variola (small pox) – portal of entry is respiratory system
- Variola major – stronger symptoms and more pox marks
- Variola minor – weaker symptoms and less pox marks
- 1ST disease that we came up w/ an artificial immunity from studies done on Cow Pox disease.
- Statistically it has been eradicated but there are still cases out there. Now we don’t give
regular immunizations against it.
--STEVE’S NOTES-BEST DAMN NOTES AROUND
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Small pox is highly contagious/communicable with a 90% mortality rate.
You don’t die from small pox, but rather secondary bacterial infections.
3.
Chicken Pox (varicella) – aka VZ virus for varicella and zoster
- Varicella virus causes chicken pox and herpes zoster causes shingles
- Portal of entry again is the respiratory system (mortality is usually only seen in adults)
- In the case of zoster, it can remain latent in the body for years. The virus enters peripheral
nerves and travels to DRG and it hangs out there as viral DNA.
- Body can’t get B and T cells in there and antibiotics won’t enter the CNS easily.
- Something triggers this viral DNA to become activated and symptoms appear, showing up
along cutaneous sensory nerves (dermatomal pattern)
- No treatment available except for those prescribed for treating the pain and inflammation.
- In the case of varicella, Reye’s Syndrome may be a problem if you give the kid aspirin to
alleviate symptoms. Child begins vomiting and showing neurological disturbances and
ultimately end up in a coma and can die. No aspirin for inflammation from chicken pox!!!
4.
Herpes – means to creep or crawl (2 types)
- Simplex 1 – virus that causes cold sores and fever blisters. This is not due to kissing or
drinking after someone. Virus is everywhere and only appears when immune system is
suppressed (ex. when you get the flu or are stressed out, cold sores appear).
Characteristically found above the waist.
- Simplex 2 – this is a mutation of simplex 1. This one is seen in sexual transmission from an
infected person. Cold sores are still present but now are seen on genitals. There is no cure for
simplex 2 and the sores will always come back when immune suppressed. Acyclovir drug is
used to interfere w/ viral replication but it is not a cure.
Characteristically found below the waist.
5.
Rubeola (aka 3 day measles)
- Portal of entry is the respiratory system and is very infectious
- Humans are the only animals that contract the measles (seen mainly in children)
- Key characteristics of rubeola are Koplik Spots. These are red, raised bumps w/ white centers
inside the cheeks. These are indicators that the child will contract measles in a few days.
6.
Rubella (aka German measles)
- Portal of entry is respiratory system
- This is a minor infection seen in children. It presents as a red rash but no red, raised bumps
and no Koplik Spots.
- If a female is pregnant in the 1 ST trimester, there is a high chance of giving birth to a
compromised baby (neurological problems mainly but cardiovascular problems also occur)
These problems come about b/c the virus is incorporated into the fetus’s DNA
- Never give rubella vaccine to a female w/o a pregnancy test first!!!
NERVOUS SYSTEM DISEASES
1. Bacterial Meningitis
- 3 bacteria cause 70% of meningitis
- Strep pneumonia (gram +), Nisseria Meningitis (gram -), Homophylus Influenza (gram -)
- H. Influenza causes meningitis, pneumonia, ear infections, and epiglottis infections. Usually
occurs in children under 4 yrs. of age. It is an encapsulated organism and this makes it hard to
kill. HIB vaccine is used against H. Influenza. Vaccines for meningitis are not very effective
due to blood brain barrier.
- Classic signs/symptoms of meningitis are: fever, red rash, sore neck and headache.
--STEVE’S NOTES-BEST DAMN NOTES AROUND
2. Meningococcal Meningitis
- Caused by Neisseria bacteria (gram – cocci w/ a capsule)
- Some people carry this in their upper respiratory tract w/o ever having symptoms. So they
sneeze and cough on everyone they come in contact w/ and spread the bacteria.
- This type of meningitis is most prevalent in areas of people in close approximation such as
day cares, dorms, barracks…
- From time of entry in our body, these bacteria could kill us w/in 24 hours!!! Vaccine for this
infection is not effective on people under 4 years old.
3. Pneumococcal Meningitis
- Caused by strep pneumonia bacteria (gram +) and they also have capsules.
- By ages of 1-4 years old we begin developing immunity to these bacteria.
- For all 3 types of meningitis, you can get a spinal tap to determine which bacteria are present.
Normal spinal (CSF) fluid is clear, but in these cases, it is milky white b/c of infection.
4.
Tetanus
- Caused by Claustridium tetani bacteria (gram + spore former) and has a terminal spore at the
end of the organism.
- These bacteria is found in the ground so if you puncture your skin by something found
outside, like a nail, glass, wood…this organism may be present. If organism is introduced
into body, it quickly begins producing exotoxins that affect the nervous system, causing
uncontrollable contractions and seizures.
- These tetanus bacteria also cause Lock Jaw. This occurs when the concentration of the
exotoxin that is produced is slightly higher than the concentration of antibody from a tetanus
shot.
- If you have classic tetanus you also have lockjaw, but if you have lockjaw you don’t have
classic tetanus.
- For tetanus reaction to happen you need…
 Tetanus bacteria
 Necrotic tissue around the portal of entry
 Organism must be presented in an anaerobic condition
5.
Botulism
- Caused by Claustridium botulinum (also a spore former and produces exotoxins)
- These bacteria are also found outside in alkaline environments such as on vegetables in a
garden.
- Example of canning green beans w/o boiling them. You open them up a few months later and
warm them up (again not boiling them) and eat them. A few hours later you start
experiencing intoxication-like symptoms and then you are dead!
- This organism has no smell or taste and b/c of the spore forming ability, it can stay dormant
for years as a spore. The one good thing is that these bacteria are very sensitive to high heat.
So, make sure you always boil things out of the garden or any canned food for that matter.
- Classic symptoms of botulism infection are diplopia, slurred speech, dysphagia and
dysmetria.
- Did you know that it would only take ½ pound of liquid botulism in the world’s water supply
could kill everyone on the planet? This is some nasty stuff, so be careful.
6.
Leprosy
- Caused by mycobacterium leprae (an acid fast bacteria)
- This is the only bacteria that grows in the peripheral nervous system
- This bacteria has never been grown on artificial media; it is grown on armadillos
- Also known as Hansen’s Disease, it is a very old disease
- Not highly contagious but we used to send people w/ leprosy to leper colonies
- Leprosy comes in 2 forms…
 Neuroleprosy – affects skin and nerve endings
 Progressive leprosy – this is neuroleprosy that spreads (lose fingers, toes, nose)
--STEVE’S NOTES-BEST DAMN NOTES AROUND
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Leprosy has been on the rise b/c of illegal immigrants bringing it into other countries
VIRAL INFECTIONS OF THE NERVOUS SYSTEM
1.
Poliomyelitis – aka infantile paralysis (3 types … I, II, III)
- Seen in 4 forms (all four forms have almost identical viruses)
 Silent – symptoms usually found in GI tract
 Abortive – fever illness w/ GI upset w/ flu-like symptoms
 Non Paralytic – initial neuromuscular involvement/paralysis, not permanent
 Paralytic – permanent neuromuscular involvement/paralysis
- Type I includes silent and abortive forms
- Type II includes non-paralytic
- Type III includes paralytic
- You will have permanent immunity to the type you came in contact w/ but no immunity for
the others…this is called serological immunity.
- We still don’t know how polio is transmitted, but we know it only affects primates (humans,
monkeys and apes)
2.
Rabies – aka hydrophobia (this is an RNA virus)
- Neurological viral disease found in all warm-blooded animals
- Most prevalent animals for carrying rabies are skunks, raccoons and squirrels
- Negri Bodies – these are inclusion bodies found in brain tissue of animals w/ rabies. These
are the brain’s way of closing off the virus from damaging the brain.
- This is the only disease we vaccinate for AFTER exposure. We do this b/c the incubation
period of rabies in humans is about 2-4 weeks. This way, the body has time to develop
antibodies.
- Rabies is sometimes called hydrophobia b/c the throat of an infected animal becomes sore,
swollen and irritated. This hurts the animal whenever it tries to swallow, therefore, you won’t
see the animal drink water. Also, the secretions of the mouth will not be swallowed either,
thus leading to the foaming of the mouth when the animal breathes out of their mouth.
3.
Encephalitis – inflammation of the brain
- Sometimes called the Sleeping Disease b/c victims usually slip into a coma and die.
- 4 viruses are known to cause encephalitis…
 Eastern, Western, Venezuelan, St. Louis (all named for location of outbreaks)
 Eastern virus is the most serious w/ a mortality rate of 70%
- Encephalitis is a seasonal viral disease seen mostly in early and mid summer during periods of
high amounts of rain and standing water. The standing water is a breeding ground for
mosquitoes, which are the main carriers of encephalitis.
- Encephalitis causes brain to swell inside cranial cavity leading to brain tissue damage and
ultimately necrosis of badly damaged tissue.
FUNGAL DISEASES OF THE NERVOUS SYSTEM
1.
Crytococcus Meningitis – fungus found in soil and pigeon poop
- This is a yeast that reproduces by budding
- Easy to diagnose by making a slide w/ India ink stain…very easy to see.
PROTOZOAN DISEASES OF THE NERVOUS SYSTEM
1.
African Trypanosomiasis – also known as African Sleeping Disease
- This protozoa is transmitted by tsetse flies
- High mortality rate (coma  death)
--STEVE’S NOTES-BEST DAMN NOTES AROUND
PRION DISEASES OF THE NERVOUS SYSTEM
A prion is a self-replicating protein w/ slow incubation period. This turns brain tissue into a spongy goo.
1.
Sheep Scrapie
- Prion disease in which sheep constantly rub themselves against something until all that tissue
on that side is gone…leading to secondary infections.
2.
Creutzfeldt – Jakob Disease (CJD)
- Hardly ever seen anymore and not known how it is transmitted
3.
Bovine Spongiform Encephalopathy (BSE)
- Thought to be the transmitter of CJD
- This is seen mainly in sheep and cow brain tissue
- Thought to have developed from grinding up sheep and cow parts and adding them to regular
feed of other sheep and cows. Cause is tainted feed w/ infected sheep and cow parts.
- Also known as Mad Cow Disease
--STEVE’S NOTES-BEST DAMN NOTES AROUND