Necrotizing soft tissue infection

Classification

Although it is classically divided into Type 1 (polymicrobial) and Type 2 (monomicrobial), others have proposed an extension to include Type 3 (water-associated) and Type 4 (fungal).

• Type 1: polymicrobial, including Staphaureus, Gram-negatives, and anaerobes
• Type 2: monomicrobial Group A Streptococcus (Strep. pyogenes)
  • May include Staphylococcus aureus, Clostridium (penetrating trauma, soil exposure), Vibrio (water), Aeromonas (water)
• Type 3: monomicrobial Gram-negative infections, generally caused by water-associated Vibrio vulnificans or Aeromonas hydrophila
• Type 4: fungal, caused by Candida species, and exceedingly rare

Management

• Surgical debridement!
• Empiric antibiotics
  • Piperacillin-tazobactam
  • Clindamycin, for synergy and the Eagle phenomenon and decreased toxin production
  • +/- vancomycin
• Then narrow based on the Gram stain an culture
• Can consider IVIg, rarely, in toxic shock syndrome

Eagle Effect

• Originally, referred to decreased effectiveness of penicillins at high concentrations
• Now, refers to decreased effectiveness of penicillins at high bacterial burden (when in stationary phase)
• Clindamycin kills enough of the bacteria that are in stationary phase that the bacteria return to logarithmic growth phase, where penicillins are more effective

Further Reading

• RCT of IVIG: Madsen MB et al. Immunoglobulin G for patients with necrotising soft tissue infection (INSTINCT): a randomised, blinded, placebo-controlled trial. Intensive Care Med. 2017;43:1585-93.