Approach to microbiologic diagnosis of necrotizing infections

Presence of gas in soft tissue (on radiographic imaging)*

Polymicrobial (gram-positive cocci, gram-positive rods, gram-negative cocci, and gram-negative rods)

Necrotizing fasciitis type I (polymicrobial)

Necrotizing cellulitis: Nonclostridial anaerobic (crepitant) cellulitis

Gram-positive rods

Acute clinical presentation

Clostridial myonecrosis (gas gangrene)

C. perfringens – Traumatic

C. septicum – Spontaneous

C. sordellii – Gynecologic

Indolent clinical presentation

Clostridial (anaerobic) cellulitis

C. perfringens – More common

C. septicum – Less common

Absence of gas in soft tissue (on radiographic imaging)*

Gram-positive cocci

Necrotizing fasciitis type II (monomicrobial)

Group A Streptococcus or other beta-hemolytic streptococci

Staphylococcus aureus (methicillin-sensitive [MSSA] or methicillin-resistant [MRSA])

Necrotizing myositis due to group A Streptococcus or other beta-hemolytic streptococci

Gram-negative rods

Aeromonas species – Freshwater exposure

Vibrio species – Saltwater exposure

* Radiographic imaging can be useful to help determine if necrotizing infection is present but should not delay surgical intervention when there is crepitus on examination or rapid progression of clinical manifestations. The most useful radiographic finding is presence of gas in soft tissues; computed tomography is the most sensitive radiographic modality for detection of this finding.

Graphic 116305 Version 2.0

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Approach to microbiologic diagnosis of necrotizing infections