Flesh eating bacteria

Definition

Flesh-eating disease is more properly called necrotizing fasciitis, a rare condition in which bacteria destroy tissues underlying the skin. This tissue death, called necrosis or gangrene, spreads rapidly. This disease can be fatal.

Description

Although the term is technically incorrect, flesh-eating disease is an apt descriptor: the infection appears to devour body tissue. Media reports increased in the mid-1990s, but the disease is not new. Hippocrates described it more than three millennia ago and thousands of reports exist from the Civil War.

Flesh-eating disease is divided into two types. Type I is caused by anaerobic bacteria, with or without the presence of aerobic bacteria. Type II, also called hemolytic streptococcal gangrene, is caused by group A streptococci; other bacteria may or may not be present. The disease may also be called synergistic gangrene, among other terms.

The arms and legs are most often affected, but the infection may appear anywhere. For example, Fournier's gangrene is flesh-eating disease in which the infection encompasses the external genitalia.

Causes & symptoms

In nearly every case, a skin injury precedes the disease. As bacteria grow beneath the skin's surface, they produce toxins. These toxins destroy superficial fascia, subcutaneous fat, and deep fascia. In some cases, the dermis and the underlying muscle are also affected.

Initially, the infected area appears red and swollen and feels hot. The area is extremely painful. Over the course of hours or days, the skin may become blue-gray, and fluid-filled blisters may form. As nerves are destroyed the area becomes numb. An individual may go into shock and develop dangerously low blood pressure. Multiple organ failure may occur, quickly followed by death.

Diagnosis

The appearance of the skin, paired with pain and fever raises the possibility of flesh-eating disease. An x ray, magnetic resonance imaging (MRI), or computed tomography scans (CT scans) of the area reveals a feathery pattern in the tissue, caused by accumulating gas in the dying tissue. Necrosis is evident during exploratory surgery, during which samples are collected for bacterial identification.

Treatment

Rapid, aggressive medical treatment, specifically, antibiotic therapy and surgical debridement, is imperative. Antibiotics may include a penicillin, an aminoglycoside or third-generation cephalosporin, and clindamycin or metronidazole. Analgesics are employed for pain control. During surgical debridement, dead tissue is stripped away. After surgery, patients are rigorously monitored for continued infection, shock, or other complications. If available, hyperbaric oxygen therapy can also be used.

Prognosis

Flesh-eating disease has a fatality rate of about 30%. Diabetes, arteriosclerosis, immunosuppression, kidney disease, malnutrition, and obesity are connected with a poor prognosis. Older individuals and intravenous drug users may also be at higher risk. The infection site also has a role. Survivors may require plastic surgery and may have to contend with permanent physical disability and psychological adjustment.

Prevention

Flesh-eating disease, which occurs very rarely, cannot be prevented.

Key Terms

Aerobic bacteria

Bacteria that require oxygen to live and grow.

Anaerobic bacteria

Bacteria that require the absence of oxygen to live and grow.

CT scan (computed tomography scan)

Cross-sectional x rays of the body are compiled to create a three-dimensional image of the body's internal structures.

Debridement

Surgical procedure in which dead or dying tissue is removed.

Dermis

The deepest layer of skin.

Fascia, deep

A fibrous layer of tissue that envelopes muscles.

Fascia, superficial

A fibrous layer of tissue that lies between the deepest layer of skin and the subcutaneous fat.

Gangrene

An extensive area of dead tissue.

Hyperbaric oxygen therapy

A treatment in which the patient is placed in a chamber and breathes oxygen at higher-than-atmospheric pressure. This high-pressure oxygen stops bacteria from growing and, at high enough pressure, kills them.

MRI (magnetic resonance imaging)

An imaging technique that uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct images of internal structures.

Necrosis

Abnormal death of cells, potentially caused by disease or infection.

Subcutaneous

Referring to the area beneath the skin.

Further Reading

For Your Information

Periodicals

• Kotrappa, Kavitha S., Radhey S. Bansal, and Navin M. Amin. "Necrotizing Fasciitis." American Family Physician 53 (May 1996): 1691.
• Meltzer, Daniel L., and Martin Kabongo. "Necrotizing Fasciitis: A Diagnostic Challenge." American Family Physician 56 (January 1997): 145.
• Ruth-Sahd, Lisa A., and Mary Pirrung. "The Infection That Eats Patients Alive." RN 1997 (March 1997): 28.

Gale Encyclopedia of Medicine. Gale Research, 1999.