Micro Virulence Factors
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| Protein A (organism & function?) | Staph Aureus. Binds Fc region of Ig. Disrupts opsonization and phagocytosis
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| 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).
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| 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)
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| 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
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| 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.
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| A-B toxin inactivates elongation factor (EF-2) (organism & function?) | Corynebacterium diphtheriae.
Causes pharyngitis and "pseudomembrane" in throat
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| 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.
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| A-B toxin permanently disables Gi (organism & function?) | Bordetella pertussis.
Increases cAMP; causes whooping cough; inhibits chemokine receptor, causing lymphocytosis.
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| 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.
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| alpha toxin (organism & function?) | Clostridium perfringens.
Causes gas gangrene & double zone of hemolysis on blood agar.
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| Edema factor (organism & function?) | Bacillus anthracis.
Edema factor is adenylate cyclase, which increases cAMP; impairs neutrophil function and causes massive edema
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| Cleaves host cell rRNA (thus inactivating 60S ribosome) | Shiga toxin from Shigella.
The toxin also enhances cytokine release, causing HUS
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| Streptolysin O (organism & function?) | S. pyogenes.
A hemolysin, that is used as an antigen for ASO antibody used in the diagnosis of rheumatic fever
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