Strep A necrotizing fasciitis

Definition
Strep A necrotizing fasciitis -- sometimes called the "flesh-eating bacteria" -- is a severe, invasive infection of the deep fascia, the tissue that covers and separates the muscles. Necrotizing fasciitis is considered a life-threatening condition.

Causes/associated factors
Strep A necrotizing fasciitis is caused by group A streptococcus (GAS), a type of bacterium commonly found on the skin and in the throat. In fact, group A streptococcus is one of the most common types of infection-causing bacteria. Most GAS infections cause only mild illnesses, such as strep throat or impetigo (a contagious, superficial skin condition).
If the bacterium is able to penetrate into areas it's not normally found, such as deep in the muscles, necrotizing fasciitis may develop and spread rapidly through the soft tissues of the body. Although necrotizing fasciitis is uncommon, it appears to be increasing in frequency and severity. The condition can develop in anyone -- even young, healthy adults -- but people who have weak immune systems are at higher risk of serious infection, including:

children who have chickenpox
older adults
people who have diabetes
people taking steroids or chemotherapy
people receiving kidney dialysis
IV drug abusers
people who have recent traumas, such as a surgical incision
people who have HIV (the virus that causes AIDS)
people who have recent burns
people who have alcoholism or peripheral vascular disease

Transmission
Group A strep fasciitis most often starts in a minor wound. Minor cuts, abrasions, insect bites or other breaks in the skin have all been portals of entry for GAS. In other cases, such as with a closed muscle trauma or muscle overuse, the infection develops without a break in the skin. You may not even be aware that you have an injury. Researchers are continuing to study how the infection develops in these cases.

Signs/symptoms
Early signs of strep A necrotizing fasciitis are often mild, which can lead to a delay in an accurate diagnosis. Symptoms progress rapidly, however, and may include:
fever
severe pain at the infection site
redness and swelling of the affected area (Most cases of necrotizing fasciitis involve the extremities, but an infection may develop in other parts of the body.)
dark red or purple blisters
abnormally dark skin or tissue
lack of feeling in the affected area

Diagnosis
Distinguishing necrotizing fasciitis from a more superficial cellulitis infection (inflammation of the cellular or connective tissue) of the skin can be difficult. A proper diagnosis is vital, however, because the treatment for these infections is quite different. If you're taking nonsteroidal anti-inflammatory medications (NSAIDs), diagnosis may be delayed because the medication can inhibit your body's inflammatory response to necrotizing fasciitis.
The doctor will ask questions about your medical history and do a physical exam. You will need blood tests, and samples of any wound drainage will be studied in a lab. The doctor may also recommend one or more of the following:

an X-ray, which is helpful in diagnosing gas trapped in the soft tissues, indicating possible group A streptococci
computed tomography (CT scan -- a computer-generated, cross-sectional picture of internal body parts)
magnetic resonance imaging (MRI, an imaging technique based on computer analysis of the body's response to a magnetic field)
The most accurate procedure to diagnose necrotizing fasciitis is a surgical biopsy of the affected site (taking a tissue sample for further evaluation). Surgery also allows the doctor to see the affected area and the extent of infection, which helps guide treatment choices.


Treatment
Treatment requires prompt and aggressive drainage and surgical removal of infected tissue. In some cases, a large portion of the surrounding tissue is also removed. Repeated surgery may be needed until the infection is controlled. You may also be given high doses of a broad spectrum antibiotic (one that's effective for many types of bacteria) until test results indicate a specific type or types of bacteria. The doctor may also suggest hyperbaric oxygen therapy (receiving oxygen that's under greater than normal atmospheric pressure), as well as nutritional support and pain relievers. Plastic surgery is often needed for functional or cosmetic purposes.

Complications
Delayed diagnosis and treatment contributes to a poorer outcome, but even with the best care necrotizing fasciitis can lead to:
gangrene of the skin (tissue death typically caused by inadequate blood supply to the area)
the death of underlying muscle tissue
the spread of inflammation along the pathways of the fascia
scarring and deformity
amputation of an extremity
The condition may also be fatal.


Pregnancy-specific information
Pregnancy is not a risk factor for necrotizing fasciitis.

Senior-specific information
Older adults often have predisposing factors such as diabetes, peripheral vascular disease or chemotherapy treatments. If you experience any of the symptoms described above, seek medical treatment immediately.

Prevention
Keep skin wounds clean and be aware of signs of infection, such as increased redness, swelling, drainage or pain at the site. If you have an infected wound or signs of infection at the site of a closed muscle injury, seek prompt medical attention.
This infection rarely starts with a sore throat but to prevent group A strept infections, wash your hands often -- especially after coughing or sneezing. If you have a sore throat, consult your doctor to decide if you need a throat culture to rule out a strep infection. (If you do have strep throat, you'll be given antibiotics. Consider yourself contagious until you've been on antibiotics for 24 hours.)

Note: Studies indicate that the use of NSAIDs during chickenpox infections may increase the risk of developing necrotizing fasciitis for both children and adults, but this remains controversial. If you have chickenpox, consult your doctor before taking any medications.