Infection Context: Necrotizing Fasciitis

The deep skin and soft tissue infections (SSTIs) mainly caused by group A Streptococcus include necrotizing fasciitis and muscle necrosis. Necrotizing fasciitis is a deep-tissue infection of the subcutaneous tissue that leads to fat and fascia’s rapid and progressive destruction. NF may be either monomicrobial (type II), where group A Streptococcus (GAS) alone or in combination with Staphylococcus aureus is the most common cause, or polymicrobial (type I), where a mixture of Gram-positive and Gram-negative aerobes and anaerobes is identified. Monomicrobial NF is more frequently seen in “community-acquired” or “idiopathic” cases, while polymicrobial causes are typical after head and neck surgeries or Fournier’s gangrene (genitourinary tract and perianal regions). Risk factors for group A Streptococcus SSTIs include minor traumas, recent varicella zoster virus infections (which can lead to superinfection), diabetes, and use of nonsteroidal anti-inflammatory drugs, and it can occur in healthy individuals as well (Davies et al. N Engl J Med 335:547–54, 1996). Group A Streptococcus necrotizing fasciitis was once considered rare, but population-based studies estimate that there are as many as 1500–3000 cases per year (Carapetis et al. Lancet Infect Dis 5:685–94, 2005). Despite intensive research, the essential questions about the pathogenesis of group A Streptococcus in NF remain unanswered (Olsen and Musser, Annu Rev Pathol 5:1–31, 2010).