Necrotizing Fasciitis

Two Types:

Type I necrotizing fasciitis is a mixed infection caused by aerobic and anaerobic bacteria. Risk factors include diabetes, peripheral vascular disease (PVD), immune compromise, and recent surgery, including minor procedures such as circumcision in newborn infants. Patients with diabetes and/or PVD frequently have lower extremity involvement. Neonates usually have abdominal or perineal involvement.

Type II necrotizing fasciitis due to group A Streptococcus (GAS) (including S. pyogenes, S. pneumo, and S. viridans, including S. mutans, as opposed to Group B Strep: S. agalactiae) or other beta-hemolytic streptococci, either alone or in combination with other species, most commonly S. aureus. It can occur among healthy individuals with no past medical history, in any age group [6]. 

Predisposing factors include a history of skin injury, such as laceration or burn, blunt trauma, recent surgery, childbirth, injection drug use, and varicella infection (chickenpox).

Diff Dx: deep venous thrombosis, septic arthritis, warfarin-induced skin necrosis, brown recluse spider bite, gangrene with secondary infection, and caustic destruction of fat and muscle due to street drug krokodil

Treatment: early and aggressive surgical exploration and debridement of necrotic tissue, together with broad-spectrum empiric antibiotic therapy and hemodynamic support. Surgery is indicated in the setting of severe pain, toxicity, fever, and elevated serum creatine kinase (CK) level, with or without radiographic evidence of fasciitis. Use of antibiotic therapy without debridement is associated with a mortality rate approaching 100 percent.

A carbapenem or beta-lactam-beta-lactamase inhibitor, plus

Clindamycin (dosed at 600 to 900 mg intravenously every eight hours in adults or 40 mg/kg per day divided every eight hours in neonates and children) for its antitoxin effects against toxin-elaborating strains of streptococci and staphylococci), plus

An agent with activity against methicillin-resistant S. aureus (MRSA; such as vancomycin, daptomycin, or linezolid). In neonates and children, vancomycin (15 mg/kg/dose every six to eight hours) is the usual empiric antibiotic for MRSA; the six-hour dosing interval is employed for sicker children.

For patients who have particular exposures that may suggest infections with specific organisms, such as trauma in fresh water (Aeromonas) or sea water (Vibrio vulnificus), it is appropriate to ensure that empiric therapy includes antimicrobial agents active against such organisms.