Infectious Disease Compendium

Necrotizing fasciitis

Diagnosis

An acute, usually rapidly progressive, necrotizing soft tissue infection. Often anesthetic over the infection. It can involve the skin (cellulitis), the muscle (myositis) and/or fascia (fasciitis). From a practical point of view, it is the surgeon who decides the extent of infection when she debrides it. I am soooo PC.

Epidemiologic Risks

Diabetes, trauma, surgery, bad luck. I tend to favor NSAIDS as a risk for streptococci although the data is variable (PubMed).

Microbiology

- Mixed synergistic necrotizing fasciitis: streptococci plus anaerobes plus coliforms.

- Meleney's: an indolent infection in abdominal wounds, often of diabetics, due to a combination of Group A Streptococcus and Staphylococcus aureus.

- Aeromonas hydrophilia: after fresh water trauma or use of leeches. Really. The plastic surgeons use leeches and the leech requires Aeromonas to exist in its gut to live. Once you treat the aeromonas, the leech will die.

- Klebsiella pneumoniae. In Taiwan (and elsewhere) it is a cause on mono-microbial necrotizing fasciitis (Pubmed).

- Vibrio vulnificus salt water exposure in patients with hepatic disease, diabetes mellitus, chronic renal insufficiency, and adrenal insufficiency (PubMed).

- Gas Gangrene: C. perfringens.

- Group A Streptococcus: especially with prior NSAID use or trauma.

- Staphylococcus aureus: especially MRSA that makes the Panton-Valentine leukocidin. In some series it is the most common cause of nec fasc (Ref). Cirrhotic patients (in Taiwan) had monomicrobial infections mainly by gram-negative rods (GNBs) (76%), including Vibrio (36%), Klebsiella (21%), and Aeromonas spp. (14%) (PubMed).

Empiric Therapy

They all require debridement. Then

- Mixed synergistic necrotizing fasciitis: (third generation cephalosporins PLUS metronidazole) OR carbapenems OR (quinolone PLUS metronidazole) OR penicillin/beta-lactamase inhibitors ALL SELECTIONS +/- aminoglycosides if septic.

- Meleney's: Nafcillin / oxacillin OR cefazolin OR vancomycin OR linezolid. - Gas Gangrene: Penicillin PLUS clindamycin.

- Group A Streptococcus: Penicillin PLUS clindamycin PLUS 1g/kg IVIG day one, 0.5 g/kg day 2 and 3.

- S. aureus: Vancomycin (it is usually MRSA) PLUS clindamycin PLUS 1g/kg IVIG day one, 0.5 g/kg day 2 and 3.

Pearls

While IVIG is (relatively) proven for streptococcal toxic shock syndrome, it's use for Strep and staph necrotizing soft tissue infection is not proven. I am a believer in IVIG in these circumstances.

Rants

Hyperbaric you ask? I remain skeptical. If you are going to use it, use AFTER debridement and AFTER antibiotics. I remember once I was asked by a doctor what I thought about hyperbaric. I said it was great for the bends, but primarily served to make hyperbaric doctors richer. Why do you ask? Turns out he was the medical director of the hyperbaric chamber. Oops. Open mouth, insert foot.