A life-threatening subcutaneous soft-tissue infection that requires a high index of suspicion for diagnosis.
Infection may be polymicrobial in aetiology (type I) due to mixed anaerobic/facultative anaerobic organisms, or due to a single organism, Streptococcus pyogenes , also called group A streptococcus (type II).
Necrotising fasciitis should be suspected in any patient with a soft-tissue infection accompanied by prominent pain and/or anaesthesia over the infected area, or signs and symptoms of systemic toxicity such as fever or hypothermia, tachycardia, tachypnoea, and/or hypotension.
Diagnosis should be aggressively pursued by surgical consultation. Treatment should not be delayed while awaiting microbiological and imaging investigations.
Indications for hospital admission for patients with soft-tissue infection may include the presence of SIRS (systemic inflammatory response syndrome). Hospital admission is essential for patients presenting with suspected necrotising fasciitis. Signs that raise suspicion for necrotising fasciitis include the presence of hypotension and/or elevated creatinine, elevated CK, elevated C-reactive protein (>124 nanomol/L [13 mg/L]), elevated WBC count with marked left shift, and/or low serum bicarbonate.
Definitive treatment is surgical debridement, repeated as necessary. Adjunctive antibiotic therapy is a crucial aspect of management, and should provide coverage for the major bacterial aetiological agents, as well as consideration of streptococcal toxic shock that can often accompany type II necrotising fasciitis.
Necrotising fasciitis is a life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not into the underlying muscle. The causal organisms may be aerobic, anaerobic, or mixed flora. Two main clinical forms exist. Type I necrotising fasciitis is a polymicrobial infection with an anaerobe such as Bacteroides or Peptostreptococcus and a facultative anaerobe such as an Enterobacteriaceae or non-group A streptococcus.      Type II necrotising fasciitis is most commonly a monomicrobial infection with Streptococcus pyogenes (group A streptococci).       
Wade Hampton Frost Professor of Epidemiology
Professor of Medicine
Microbiology and Pathology
Division of Infectious Diseases and International Health
University of Virginia
WAP declares that he has no competing interests.
Assistant Professor of Medicine
Division of Infectious Diseases
University of Vermont
CH declares that he has no competing interests.
Professor of Infectious Diseases and Hon. Consultant
Section of Infectious Diseases
Imperial College London
SS declares that she has no competing interests.
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