S. aureus is a pyogenic pathogen known for its capacity to induce abscess formation.
- Invasive disease: For invasive S. aureus infection to occur, some or all of the following steps are necessary:
- - Colonization/inoculation: Bacteria colonize tissue surfaces or are inoculated directly into tissue—e.g., as a result of minor abrasions or via IV access catheters.
- - Invasion: Bacteria replicate at the site of infection and elaborate enzymes that facilitate survival and local spread. CA-MRSA isolates that produce the Panton-Valentine leukocidin toxin have been linked to more serious infections.
- - Evasion of host defense mechanisms:S. aureus possesses an antiphagocytic polysaccharide microcapsule that facilitates evasion of host defenses and plays a role in abscess formation. Organisms can survive intracellularly and then cause recrudescent infections when conditions are suitable.
- - Metastatic spread:S. aureus can survive in PMNs and may use these cells to spread to and seed other tissue sites.
- Toxin-mediated disease: S. aureus produces three types of toxin: cytotoxins, pyrogenic toxin superantigens, and exfoliative toxins.
- - Antitoxin antibodies are protective against toxin-mediated staphylococcal illness.
- - Enterotoxins and toxic shock syndrome toxin 1 (TSST-1) act as “superantigens” or T-cell mitogens and cause the release of large amounts of inflammatory mediators, producing multisystem disease that includes fever, rash, and hypotension.