1.Capsular polysaccharide – inhibits neutrophilphagocytosis
and chemotaxis. Present on cell surface.
2.Protein A – binds Fc (cell receptor) portion of some forms of
IgG, neutralizing the ability of phagocytic cells to recognize it.
Antibody is bound to cell “in reverse.”
3. Exfoliative toxins: ETA and ETB – responsible for SSSS.
Superantigens.
4. Enterotoxins: eight distinct toxins; responsible for S. aureus
food poisoning. Some can take the place of
TSST-1 in nonmenstrual TSS.
Stable to heat, gastric and jejunal enzymes.
stimulate inflammatory mediators; stimulate vagus nerve
endings, producing severe vomiting.
Superantigens.
5. Toxic shock syndrome toxin (TSST-1): triggers massive
release of cytokines that cause shock and death.
Superantigens.
6. MSCRAMMs/Adhesins: (Microbial Surface Components Recognizing Adhesive Matrix Molecules)
Bind to extracellular matrix/host cells – many different factors are synthesized by S. aureus and allow the bacterium to adhere to a variety of host molecules.
7. Yellow pigment. Caratenoid. Protects organism from reactive oxygen species (released by neutrophils)
Cytoxins
8. Alpha, beta, gamma, delta toxins: can
lysea variety of cell types (including red blood
cells).
Alpha toxin: does not lyseneutrophils efficiently
9. Panton-Valentine leukocidin: Does not lyse red
blood cells as efficiently as other S. aureuscytotoxins.
Role in pathogenesis unclear.
Encoded on the genome of most strains of CA S.aureus.
10. Peptidoglycan: component of cell wall; has endotoxin- like activity; stimulates production of endogenous pyrogens activation of complement, production of IL-1 from monocytes aggregation of neutrophils (part of abscess formation)
11. PBP2A - penicillin binding protein. Involved in cell wall biosynthesis. Mediates methicillin resistance.
Encoded by mecA gene.
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