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- Staphylococcus genus (Staph): gram-positive beta-hemolytic bacteria; occur singly, in pairs, short chains and clusters (from Greek staphylé, "bunch of grapes"). Ubiquitous colonizers of skin and mucous membranes, esp anterior nares.
- S. aureus (SA), coagulase positive.
- Coagulase negative Staph (CoNS) >30 species, 15 of which are human pathogens.
- S. epidermidis, S. saprophyticus (novobiocin resistant), S. haemolyticus, S. lugdunensis and S. schleiferi most common.
- SA produces several toxins 
- Membrane-damaging toxins
- Superantigens (enterotoxins and toxic shock syndrome toxin [TSST])
- Enzymes (exfoliative toxins - staphylococcal scalded-skin syndrome)
- Staph grow rapidly on blood agar and other non-selective media, can survive harsh environmental conditions (high salt media), and are relatively heat-resistant.
- Methicillin resistance: >80% of CoNS, and an increasing number of both hospital-acquired & community-acquired MRSA. Vancomycin-intermediate resistance (VISA) and vancomycin-resistant strains have emerged.