PATHOGENS

• Some classify necrotizing fasciitis (NF) into Type I and Type II.
  • Mixed aerobic-anaerobic bacteria [Type I]
  • Group A Streptococcus (GAS, S. pyogenes, Type II)
    • Thought to be the most common cause. CDC estimates ~ 700-1150 cases/yr annually since 2010.
      • Tracked by the CDC through their Active Bacterial Core surveillance program.
    • Certain streptococcal strains are seen more frequently in NF, most commonly those that contain M protein types 1, 3, 12, and 28 (elaborating pyrogenic exotoxin A).
    • May complicate routine varicella or zoster as superinfeciton.
  • Some also use Type III, designating NF due to clostridial causing gas gangrene.
    • Clostridia perfringens is the most common; see module for details.
      • Other Clostridial spp. include C. noyyi, C. septicum, C. histolyticum and C. sordelli.
• Other pathogens that may cause NF:
  • Other Streptococcal species
  • Staphylococcus aureus
  • Vibrio vulnificus
  • Aeromonas spp.
  • Klebsiella spp.
  • Pseudomonas aeruginosa
  • Other: host of occasional bacterial pathogens implicated, Candida and Mucor spp. also rarely described.