Necrotizing fascitis

A rapidly progressive, extremely destructive bacterial infection of the deep layers of the skin and fascia, often associated with Streptococcus pyogenes or mixed bacteria. In popular media, it may be called "flesh-eating bacteria". Onset is subtle, beginning with fever and chills, but, after several days, reddening of the skin, with skin lesions including vescicles or bullae containing fluid. The fever will continue to rise and there will be systemic toxicity. Mortality may be high.

It can develop at any puncture site, or where there is internal destruction as from fractures, frostbite, compartment syndrome, or surgery. Other infections, such as varicella, can make the patient vulnerable. Chronic disease, especially diabetes, may predispose to the condition.

Workup

If the lesion is probed, an instrument will pass along a plane just superficial to the deep fascia, which differentiates it from cellulitis.

A Gram stain of the fluid can guide initial antibiotic therapy.

Treatment

At least three clinical forms are recognized; all are surgical emergencies, although empirical antibiotic therapy should be started immediately. Hyperbaric oxygen therapy has been reported to be useful.

• Type I, or polymicrobial NF, usually occurs after trauma or surgery. It may present as simple cellulitis, but disproportionate pain and systemic symptoms should be warnings. A variant, saltwater necrotizing fascitis, is caused by Vibrio species, especially Vibrio vulnificus.
• Type II is the streptococcal, rapidly destructive form
• Type III is gas gangrene, from Clostridium perfringens or Clostridium septica, usually after trauma.

There has been a significant increase in cases caused by community-acquired, methicillin-resistant Staphylococcus aureus. Clindamycin, trimethoprim–sulfamethoxazole, and rifampin were effective.

Antibiotics

While high-dose penicillin G would be the drug of choice for streptococci, the danger is such that there must also be coverage for aerobes and anaerobes. Since clindamycin is an alternative for streptococci, one proposed standard regimen is gentamicin, combined with clindamycin or chloramphenicol. Ampicillin should be added if enterococci are suspected. Metronidazole or third-generation cephalosporins cover anaerobes.

Surgery

Wide excision of the affected area, under general anesthesia, is critical, and may need to be repeated several times in the first 24 hours. Compartment syndrome may also occur and need decompression.

Hyperbaric oxygen

While mortality rates of 30-50% are common, while there have not been large-scale studies of hyperbaric oxygen, it has been suggested that mortality may drop to 9-20% when it is combined with appropriate surgery and antibiotics.