In necrotizing fasciitis prompt diagnosis and early surgical debridement saves lives. The unwary doctor can get caught out by not considering this surgical emergency as part of their differential when presented with a soft-tissue infection post surgery, trauma or apparent spontaneous manifestation. The patient is more unwell than expected with a simple wound infection. A 24-hour delay in diagnosis and treatment may result in amortality rate of up to 50%.

Definition

Necrotizing fasciitis is a progressive, rapidly spreading microbial softtissue infection, which spreads along the superficial and deep fascial planes with secondary necrosis of subcutaneous tissues and ensuing sepsis.

Classification

1. ▪ Type I: polymicrobial necrotizing fasciitis mainly occurs after recent surgery or trauma. Anaerobic and facultative bacteria work synergistically (one potentiates the growth of the other).Much more common than mono-microbial necrotizing fasciitis (Type II).

2. ▪ Type II: group A streptococcus infection necrotizing fasciitis. Monomicrobial haemolytic streptococci infection. Rapid development of erythema over 24 hours with subsequent blue discolouration bullae and superficial gangrene over the ensuing days.Streptococcal toxic shock syndrome: causedby Streptococcus pyogenes. The systemic pathogenesis is induced by the superantigen M proteins which lead to release of tumour necrosis factor, interleukins 1 and 6. The rapid systemic response leads to fever, shock and organ failure.

3. ▪ Type III: clostridial necrotizing fasciitis, mainly Clostridium perfringens. A decrease in local oxygen tension results in spore activation. Gram staining reveals gram positive rods. It is associated with myonecrosis and gas gangrene.