What's unique to gram-positive organisms?
Teichoic acid in the cell wall -- induces TNF & IL-1
What's unique to gram-negative organisms?
Endotoxin (encoded within their bacterial DNA); outer cell membrane, thin murein layer, then inner cell membrane
The 5 gram-positive rods... plus the 2 other gram-positive bacteria (besides Strep & Staph)
- Bacillus, Corynebacterium, Clostridium, Listeria, & TB
- The other 2 (branching filaments): Actinomyces & Nocardia
Why can't you Gram-stain each of these? Treponema, Rickettsia, Chlamydia, Legionella, Mycoplasma, Mycobacteria
- Treponema = too thin
- Next 3 = intracellular
- Mycoplasma = no cell wall
- Mycobacteria = high lipid-content cell wall (mycolic acid), even though it is gram-pos
India ink stain is used for...
Silver stain is used for... (2)
- India = Cryptococcus
- Silver = fungus & Legionella
To culture N.gonorrhoeae, must grow on this kind of media
- Nagging Pests Must Breathe.
- Nocardia, Pseudomonas, Mycobacterium TB, Bacillus (so, it needs to form spores to protect itself when no O2)
- That's why TB likes to go to the apices of the lung for reactivation: highest PO2 there. (But, initial infection = gravity takes it down to the lower lobes when you breathe in)
Can't Breathe Air: Clostridium, Bacteroides, Actinomyces. Could easily accumulate oxidative damage. (Obviously, that means they're catalase-negative, since catalase would degrade hydrogen peroxide)
What does vibrio cholerae toxin do?
Increases NaCl pumped out of gut, thanks to inc'd Gs --> adenylyl cyclase --> cAMP
Corynebacterium diphtheriae toxin
- Inactivates EF-2 (elongation factor-2) --> pharyngitis & pseudomembrane in throat. Could get peripheral neuropathy or cardiomyopathy, too.
- Pseudomonas (Exotoxin A) also inactivates EF-2.
How does Bordetella pertussis toxin work?
Increases cAMP by inhibiting Gi. Whooping cough.
How does Clostridium tetani toxin work?
Blocks inhibitory neurotransmitter release (GABA & glycine).
How does Clostridium botulinium toxin work?
Blocks ACh release. From food that's incompletely cooked, then canned (anaerobic). Floppy baby.
How does Clostridium perfringens toxin work?
Called lecithinase; breaks down muscle & causes hemolysis. Gas gangrene.
How C.dif toxin works
Kills enterocytes --> pseudomembranous colitis (red with white exudate). Antibiotics responsible: clindamycin, ampicillin.
Generalized vs. specialized transduction
- Generalized = bacterial DNA gets trapped inside viral capsid
- Specialized = as viral DNA is excised, flanking bacterial genes may come along with it
What does catalase do?
Breaks down hydrogen peroxide, which is meant to be antimicrobial (made by PMN's)
what does coagulase do?
- Enclose the bacterium (Staph) in a fibrin clot.
- (Vs. staphylokinase: lyses clots)
Rheumatic fever: no "rheum" for SPECCulation
- Subcutaneous nodules, polyarthritis, erythema marginatum rash, chorea, carditis (mitral valve #1)
- All caused by a heart Ag similar to a Group A Strep Ag
What do enterococci cause?
They're natural GI bacteria. They cause subacute bacterial endocarditis & UTI's. Can't treat w/penicillin G.
The only bacterium with a protein capsule
Bacillus (D-glutamate), which is a gram-pos rod
The only gram-pos bacterium with endotoxin
Listeria (mild GI in healthy ppl, meningitis in neonates & immunocomp)
Gram-positive, branching filament. Part of normal oral/GI flora, but can cause oral & facial abscesses; pus has yellow sulfur granules.
Like TB: Gram-pos, acid-fast, pulm infection in immunocompromised
Ghon focus (& where is it usually found)?
- Walled-off TB (caseous granuloma, calcified). Usually found in lower lobe, since that's where primary infections take place.
- Obv, you're still PPD+ with latent TB... but acid-fast stain is only + if active infection.
TB in vertebral body
Leprosy = Hansen's disease. Damages skin & superficial nerves. 2 kinds: Lepromatous leprosy is worse (failed T-cell-mediated immunity); tuberculoid leprosy is self limited.
Gram-negative, non-lactose-fermenting rods
- P.P.S.S. Proteus, Pseudomonas (oxidase-positive), Shigella, Salmonella.
- But all of these, except Pseudomonas, are still part of the Enterobacter family
N.mengitides gets into blood --> septic shock, DIC, adrenal insufficiency
With gonorrhea, who's more likely to be asymptomatic, men or women?
Women (men will have pus & painful urination)
E.coli, Klebsiella, Proteus, Serratia, Salmonella, Shigella. HOKE: H antigen (flagella), O antigen (endotoxin), K antigen (kapsule).
Fever, rose spots on abdomen, diarrhea. Typhoid Mary = chronic carrier (in gallbladder).
Gram-negative, but no endotoxin (the only one... vs. Listeria, the only gram-pos bacterium with endotoxin). When intestine breaks open (trauma, appendicitis, ischemia), bacteria seed the intestine --> abscess.
Gram-neg spirochete that affects the liver: flu-like symptoms, abdominal pain, jaundice. Severe form = Weil's disease: both liver & kidney dysfunction (anemia, hemorrhage, azotemia). Tropics.
Stages of Lyme disease
- Caused by Borrelia burgdorferi, a Gram-negative spirochete transmitted by the deer tick in summer (mainly).
- 1) Erythema chronicum migrans (chest or butt), flulike sx
- 2) Neuro & cardiac: AV block, Bell's palsy, aseptic meningitis
- 3) Migratory polyarthritis, plus chronic monoarthritis