Staphylococcus aureus
1. Gram-positive cocci, in clusters.
2. Catalase +, Coagulase + (differentiates from other staph).
3. Golden-yellow, beta-hemolytic colonies.
4. Grows on mannitol salt agar (ferments mannitol).
5. Virulence: Protein A, coagulase, hemolysins, enzymes.
6. Toxins:
- Enterotoxin – food poisoning
- TSST-1 – toxic shock
- Exfoliative – scalded skin
7. Diseases:
- Skin (boils, impetigo)
- Systemic (pneumonia, osteomyelitis, endocarditis)
- Toxin-mediated (TSS, food poisoning)
8. MRSA: mecA gene → PBP2a → resistant to beta-lactams.
9. Treatment
- MSSA: cloxacillin
- MRSA: vancomycin/linezolid
10. Normal flora of nose, skin, causes hospital infections.
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