MICROBIOLOGY

• 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) is 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, i.e., toxic shock syndrome toxin [TSST] and enterotoxins[9]
  • Enzymes, i.e., 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-resistant S. aureus (MRSA): >80% of CoNS. Global antimicrobial surveillance trends show decline in prevalence of MRSA among bloodstream infections since 2009.[14]
• Vancomycin-intermediate resistance (VISA) and vancomycin-resistant strains are recognized.[8]