Necrotizing Fasciitis

Most commonly known as "flesh-eating bacteria," necrotizing fasciitis is a progressive, rapidly spreading inflammatory infection of the deep fascia. It's also referred to as hemolytic streptococcal gangrene, acute dermal gangrene, suppurative fasciitis, and synergistic necrotizing cellulitis.

Necrotizing fasciitis destroys the fascia and fat tissues, with secondary necrosis of subcutaneous tissue. It's most commonly caused by the pathogenic bacteria. Streptococcus pyogenes, also known as group A streptococcus (GAS), but other aerobic and anaerobic pathogens may be present. This severe and potentially fatal infection may begin at the site of a small insignificant wound or a surgical incision and is characterized by invasive and progressive necrosis of the soft tissue and underlying blood supply.

Necrotizing fasciitis has been described in medical literature since the Civil War. It accounts for 8% of reported cases of invasive GAS infections today. Men are 3 times more likely to develop this rare condition than women. The disease rarely occurs in children except in countries with poor hygiene practices.

The mean age of the population contracting the disease is 38 to 44 years of age. The mortality rate is very high at 70% to 80%. Mortality drops significantly and prognosis improves with early intervention and treatment. Aggressive treatment with surgery, antibiotics, and hyperbaric oxygen therapy has been shown to reduce the mortality rate to as low as 9% to 20% .

Causes

This disease is caused by one or more aggressively multiplying bacterial species, most often group A strep. It usually occurs in someone with some kind of underlying illness or severe injury.

Symptoms and Signs

• Fever
• General ill feeling
• Severe pain in the area
• Swelling in the area
• Bleeding into the skin
• Visibly dead (necrotic) tissue
• Patchy skin color
• Skin breaks (open wound)
• Skin around the wound feels hot and looks reddened, raised, or discolored (inflamed)
• Oozing fluid ranging from yellowish clear or yellowish bloody to puslike in quality

Diagnostic tests

Tissue biopsy is the best method of diagnosing necrotizing fasciitis. Cultures of microorganisms can be obtained locally from the periphery of the spreading infection or from deeper tissues during surgical debridement. Gram's staining and culturing of biopsied tissue are useful in establishing the type of invasive organisms and the most effective treatment against them.

Radiographic studies can pinpoint the presence of subcutaneous gases. Computed tomography scans can locate the anatomic site of involvement by locating necrosis. In combination with clinical assessment, magnetic resonance imaging is used to determine areas of necrosis and the need for surgical debridement.

Other supportive studies include laboratory values, such as complete blood count with differential, electrolytes, glucose, blood urea nitrogen and creatinine, urinalysis, and arterial blood gases.

Treatment

Prompt and aggressive exploration and debridement of suspected necrotizing fasciitis is mandatory to provide an early and definitive diagnosis and enhance the patient's prognosis. Ninety percent of patients that present with clinical signs and symptoms need immediate surgical debridement, fasciectomy, or amputation.

Penicillin, clindamycin (Cleocin), metronidazole (Flagyl), ceftriaxone (Rocephin), gentamicin (Garamycin), chloramphenicol (Chloromycetin), and ampicillin (Omnipen) are some of the medications used orally. I.V., or intramuscularly to combat the organisms involved with necrotizing fasciitis. The particular drugs used are determined by the sensitivity of the organisms in culture. Medications in combination must be used when the infection is polymicrobial. Drug recommendations continue to change as new antibiotics are developed and new resistance emerges.

Hyperbaric oxygen therapy (HBO) may decrease the mortality rate and significantly improve tissues' defense against infection. HBO prevents necrosis from spreading by increasing the normal oxygen saturations of infected wounds by a thousand-fold, causing a bactericidal effect. Typical treatment involves HBO started aggressively after the first surgical debridement and continuing for 10 to 15 sessions.

Prevention

Clean any skin injury thoroughly. Watch for signs of infection such as redness, pain, drainage, swelling around the wound, and consult the health care provider promptly if these occur.

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