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Micro Virulence Fact
Micro Virulence Factors
| Question | Answer |
|---|---|
| Protein A (organism & function?) | Staph Aureus. Binds Fc region of Ig. Disrupts opsonization and phagocytosis |
| IgA protease (organism & function?) | Secreted by S. penumoniae, H. influenzae, and Neisseria. Enzyme that cleaves IgA (remember that IgA prevents attachment of bacteria and viruses to mucous membranes). |
| M protein (organism & function?) | Group A Streptococcal (aka S. pyogenes). Helps prevent phagocytosis (but Plasma cells eventually generate antibodies against M protein....so it is actually a weak part of the organism's defense) |
| Superantigens (organism & function?) | 1. S. aureus: TSST-1--toxic shock syndrome 2. S. pyogenes: erythrogenic toxin--scarlet fever Fxn: bind directly to MHC II and T-cell receptor simultaenously, activating large numbers of T cells to stimulate release of IFN-gamma and IL |
| General function of A-B toxins | B component binds to host cell surface, enabling endocytosis of organism. A component ADP ribosylates host cell protein, altering protein function. |
| A-B toxin inactivates elongation factor (EF-2) (organism & function?) | Corynebacterium diphtheriae. Causes pharyngitis and "pseudomembrane" in throat |
| A-B toxin permanently activates Gs protein (organism & function?) | Vibrio cholerae. Stimulates adenylyl cyclase; increase pumping of Cl- into gut and decreased Na+ absorption. Water moves into gut lumen; causes voluminous rice-water diarrhea. |
| A-B toxin permanently disables Gi (organism & function?) | Bordetella pertussis. Increases cAMP; causes whooping cough; inhibits chemokine receptor, causing lymphocytosis. |
| A-B toxins include Heat-labile toxin and Heat-stabile toxin (organism & function?) | E. coli. Heat-labile toxin stimulates adenylate cyclase (labile like the air) Heat-stable toxin stimulates guanylate cyclase (stable like the ground) Both cause watery diarrhea. |
| alpha toxin (organism & function?) | Clostridium perfringens. Causes gas gangrene & double zone of hemolysis on blood agar. |
| Edema factor (organism & function?) | Bacillus anthracis. Edema factor is adenylate cyclase, which increases cAMP; impairs neutrophil function and causes massive edema |
| Cleaves host cell rRNA (thus inactivating 60S ribosome) | Shiga toxin from Shigella. The toxin also enhances cytokine release, causing HUS |
| Streptolysin O (organism & function?) | S. pyogenes. A hemolysin, that is used as an antigen for ASO antibody used in the diagnosis of rheumatic fever |
Created by:
bao
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