Necrotizing Fasciitis (Flesh-Eating Bacteria) - Topic Overview

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. The most common type of bacteria causing necrotizing fasciitis is Streptococcus pyogenes.

When necrotizing fasciitis occurs in the area of the genitals, it is called Fournier gangrene.

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, including surgical wounds from operations such as an episiotomy or a hernia repair.
• Recently had chickenpox or other viral infections that cause a rash.
• Use steroid medicines, 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 infections such as strep throat and impetigo. Usually the infections caused by these bacteria are mild. But in rare cases the bacteria produce poisons (toxins) that can damage the soft tissue below the skin and cause a more dangerous infection that can spread quickly along the tissue covering the muscle (fascia). The bacteria also can travel 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 contact raw saltwater fish or oysters. Infection also may occur through injuries from handling sea animals 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. Sometimes, people who have gunshot injuries, intestinal surgery, 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.

Group A strep bacteria producing the toxins that cause necrotizing fasciitis can be passed from person to person. But a person who gets infected by 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?

A person may have pain from an injury that gets better over 24 to 36 hours and then suddenly gets worse. Often the pain is much worse than would be expected from the size of the wound or injury. Other symptoms may include fever, chills, and nausea and vomiting or diarrhea. The skin usually 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 start 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?

A person with necrotizing fasciitis usually is very sick before he or she sees a doctor. The doctor may suspect necrotizing fasciitis based on how fast the symptoms developed and how quickly the infection is progressing. 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 find out the extent and depth of the infection.

How is it 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 with 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 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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