Necrotizing Fasciitis (Flesh-Eating Bacteria)

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Topic Overview

What is necrotizing fasciitis?

Necrotizing fasciitis is a rare bacterial infection that can destroy skin and the soft tissues beneath it, including fat and the tissue covering the muscles (fascia). Because these tissues often die rapidly, a person with necrotizing fasciitis is sometimes said to be infected with "flesh-eating" bacteria, especially Streptococcus pyogenes.

Necrotizing fasciitis is very rare but serious. Around 30% of those who develop necrotizing fasciitis die from the disease.¹

Many people who get necrotizing fasciitis are in good health prior to the infection.² Those at increased risk of developing the infection are people who:

• Have a weakened immune system or lack the proper antibodies to fight off the infection.
• Have chronic health problems such as diabetes, cancer, or liver or kidney disease.
• Have cuts or surgical wounds, including episiotomy.
• Recently had chickenpox or other viral infections that cause a rash.
• Use steroid medications, which can lower the body's resistance to infection.

What causes necrotizing fasciitis?

Necrotizing fasciitis is caused by several kinds of bacteria. The most common cause is infection by a group A streptococcal (GAS) bacterium, most often Streptococcus pyogenes, which also causes other common infections such as strep throat or impetigo. Usually the infections caused by these bacteria are mild. In rare cases, however, the bacteria produce poisons (toxins) that can damage the soft tissue below the skin and cause a more dangerous infection that spreads through the blood to the lungs and other organs. The disease also may be caused by Vibrio vulnificus. Infection with this bacterium can occur if wounds are exposed to ocean water or the drippings from raw saltwater fish, or through injuries from handling marine crustaceans such as crabs. These infections are more common in people who have chronic liver diseases such as cirrhosis.

Another type of necrotizing fasciitis may be caused by multiple bacteria found in the intestine; this type most often affects people with diabetes or peripheral arterial disease. Occasionally people who have gunshot injuries or tumors in the lower digestive tract develop necrotizing fasciitis.

A break in the skin allows bacteria to infect the soft tissue. In some cases, infection can also occur at the site of a muscle strain or bruise, even if there is no break in the skin. It may not be obvious where the infection started, because the bacteria may travel through the bloodstream to other parts of the body.

The bacteria that produce the toxins that cause necrotizing fasciitis can be passed from person to person. However, a person who acquires the bacteria is unlikely to develop a severe infection unless he or she has an open wound, chickenpox, or an impaired immune system.

What are the symptoms of necrotizing fasciitis?

A person may have pain from an injury that lessens over 24 to 36 hours and then suddenly becomes much worse. Other symptoms may include fever, chills, and nausea and vomiting or diarrhea. The skin commonly becomes red, swollen, and hot to the touch. If the infection is deep in the tissue, these signs of inflammation may not develop right away. The symptoms often develop suddenly (over a few hours or a day), and the infection may spread rapidly and can quickly become life-threatening. Serious illness and shock can develop in addition to tissue damage. Necrotizing fasciitis can lead to organ failure and, sometimes, death.

How is necrotizing fasciitis diagnosed?

Usually a person is very sick with necrotizing fasciitis before a doctor is seen. Your doctor may suspect necrotizing fasciitis based on the speed with which the infection progressed and symptoms developed. A sample of the infected tissue may be taken to identify the type of bacteria causing the infection. X-rays, CT scans, or MRI scans may be done to look for injury to the organs or to assess the extent of the infection.

How is necrotizing fasciitis treated?

Immediate medical care in a hospital is always necessary. Supportive care for shock, kidney failure, and breathing problems is often needed. Most people will need surgery to stop the infection from spreading. Extensive use of antibiotics is needed to kill the bacteria.

What if I know someone with the disease?

Most people will not get necrotizing fasciitis. You generally do not have to worry about getting the disease, because the bacteria that cause the disease usually do not cause infection unless they enter the body through a cut or other break in the skin.

In very rare cases, the bacteria can be spread from one person to another through close contact such as kissing. People who live or sleep in the same household as an infected person or who have direct contact with the mouth, nose, or pus from a wound of someone with necrotizing fasciitis have a greater risk of becoming infected.

If you have been in close personal contact with someone who develops necrotizing fasciitis, there is a small chance that your doctor may recommend that you take an antibiotic medicine to help reduce your chances of getting an infection.³ If you do develop any symptoms of an infection after being in close contact with someone who has necrotizing fasciitis, see your doctor right away.

To help prevent any kind of infection, wash your hands often, and always keep cuts, scrapes, burns, sores, and bites clean.

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Last updated:	November 01, 2005
Author:	Colleen Cronin
Reviewed By:	Renée M. Crichlow, MD - Family Medicine, Dennis L. Stevens, MD, PhD - Internal Medicine, Infectious Diseases
Editors:	Susan Van Houten, RN, BSN, MBA, Lisa Shaw