Necrotizing soft tissue infections include necrotizing forms of cellulitis, myositis, and fasciitis. These infections are characterized clinically by fulminant tissue destruction, systemic signs of toxicity, and high mortality. Accurate diagnosis and appropriate treatment must include early surgical intervention and antibiotic therapy.
Several different names have been used to describe the various forms of necrotizing infections; this is related in part to naming based on clinical features rather than surgical or pathologic findings. It is important to consider the many different types of necrotizing infections described in the literature because these descriptions may provide clinical clues needed for prompt intervention and management. The lay press has referred to organisms that cause necrotizing soft tissue infections as "flesh-eating bacteria."
Issues related to necrotizing cellulitis, fasciitis, and myositis will be reviewed here. Pyomyositis and myonecrosis are discussed separately. (See "Clostridial myonecrosis" and "Pyomyositis".)
Necrotizing soft tissue infections are comprised of two distinct bacteriologic entities: type I (polymicrobial infection) and type II (group A streptococcal [GAS] infection). There are also case reports of monomicrobial necrotizing soft tissue infections due to other organisms, including Haemophilus influenzae [1-3].
●In type I infection, at least one anaerobic species (most commonly Bacteroides, Clostridium, or Peptostreptococcus) is isolated in combination with one or more facultative anaerobic streptococci (other than group A) and members of the Enterobacteriaceae (eg, E. coli, Enterobacter, Klebsiella, Proteus) (table 1) [4-6]. An obligate aerobe, such as P. aeruginosa, is only rarely a component of such a mixed infection. Necrotizing fasciitis of the head and neck is usually caused by mouth anaerobes, such as Fusobacteria, anaerobic streptococci, Bacteroides, and spirochetes. Fournier’s gangrene is caused by facultative organisms (E. coli, Klebsiella, enterococci), along with anaerobes (Bacteroides, Fusobacterium, Clostridium, anaerobic or microaerophilic streptococci) .