|
|
|
|
|
|
|
|
|
|
Archived CMA Today - Quick Clinic
Necrotizing fasciitis: The truth about “flesh-eating” bacteria
By Nicole Grasse, MA Most people know about necrotizing fasciitis from grisly media stories that refer to it as the “flesh-eating” bacteria. True to its fearsome reputation, necrotizing fasciitis—a rare bacterial infection of the soft tissue under the skin that attacks and kills tissue—can be a devastating and fatal disease. While early recognition can help significantly reduce the severity of illness and fatalities, the disease can be difficult to detect. Under the lens Necrotizing fasciitis is caused by either a combination of aerobic and anaerobic bacteria, which is known as type I necrotizing fasciitis, or by group A streptococcal (GAS) bacteria, which is known as type II.1 There is also a variant of type I that occurs when a wound is exposed to saltwater infected with Vibrio bacteria.1 The most common type of necrotizing fasciitis (type II) is due to GAS bacterial infection, which also causes strep throat and impetigo.2 The CDC estimates that between 9,000 and 11,500 cases of GAS infections occur each year.3 Most infections caused by GAS are relatively mild. However, for reasons not entirely clear to experts, the bacteria may enter the body—often through a minor cut, wound, or surgical opening—and produce toxins that will damage the soft tissue and cause a more dangerous infection that spreads rapidly along the fascia. Once this occurs, bacteria may also travel through the blood to muscles, lungs, and other organs. Due to the rapid deterioration and resulting death of tissue, this infection is sometimes referred to as “flesh-eating” strep or disease. Although rare, necrotizing fasciitis can be a devastating illness. The CDC estimates that around 25 percent of those who contract the disease die from it.3 Mysterious illness Experts don’t entirely understand why GAS develops into necrotizing fasciitis in some people but not others. Although most cases result from a wound infection, there is no break in the skin at all in some cases, according to Alan Bisno, MD, Professor Emeritus of medicine at the University of Miami, Fla., Miller School of Medicine. Some physicians believe the bacteria may originate elsewhere in the body, such as in the throat, and reach the fascia through the blood stream. “Necrotizing fasciitis can be very sneaky. It may occur in previously healthy individuals, even those without an obvious wound of any kind. About half such patients may develop streptococcal toxic shock syndrome (STSS), which doubles the chance of fatalities,” says Dr. Bisno. Not all strep bacteria are the same, notes Loren G. Miller, MD, director of the Infection Control Program at Harbor-UCLA Medical Center in Los Angeles. “Some strep have genes that produce toxins under the skin, which causes necrotizing fasciitis. We’re not sure exactly why it develops in some people and not in others,” says Dr. Miller. “It seems like bad luck or genetic disposition.” Although necrotizing fasciitis can strike people in excellent health, several conditions put people at greater risk. These include a weakened immune system, which lacks the antibodies that help fight off infections; chronic health issues, such as diabetes, cancer, liver or kidney failure; cuts or surgical wounds; chicken pox or other viruses that cause skin rashes; and steroid medications that lower the body’s resistance to infections.2 Stealthy symptoms In its early stages, necrotizing fasciitis is difficult to identify because it mimics symptoms of minor illnesses. At first glance, the disease has the appearance of a skin infection, although one telltale symptom is extreme pain, either at the site of infection or in the same region or limb. “Necrotizing fasciitis causes excruciating, relentless pain,” says Dr. Miller. “The pain is often out of proportion with that of a skin infection.” The patient may also report the exact opposite: they may experience numbness at the site because the tissue may already be dead. Other symptoms include fever and chills, nausea, and vomiting. Patients are often misdiagnosed as having a cold or flu. The location of the skin infection or wound may become red, hot, and swollen. The skin infection may spread and grow even while the patient is on antibiotics, or blisters filled with pink or purple fluid may appear. Finally, because necrotizing fasciitis can produce gas under the skin, there may be air bubbles under the tissue. “Often, the patient will look critically ill,” says Dr. Miller, who notes that symptoms may spread so rapidly that it can become life threatening in a matter of days. The patient may also have a high white blood cell count and low sodium. In addition to tissue damage, some patients may develop STSS, a severe form of shock associated with streptococcal infection that increases the fatality rate, according to Dr. Bisno. Diagnosis by surgery Once necrotizing fasciitis is suspected, the most effective method of diagnosis is surgical exploration, according to Dr. Miller. “It’s kind of like an appendicitis; you think you know what it is, but you can’t be sure until you go in and examine it surgically,” he says. Necrotizing fasciitis has a distinct surgical appearance because the muscle groups separate easily, Dr. Miller explains. “It’s the only way to figure out if it’s necrotizing fasciitis,” he says. Tests, such as X-rays, CT (computerized tomography) scans, or MRI (magnetic resonance imaging) scans, also may be necessary to find the extent of damage to the organs. Treatment and transmission A diagnosis of necrotizing fasciitis always results in immediate hospital care. When diagnosed, surgeons will remove dead tissue to eliminate the bacteria. Supportive treatment includes extensive use of antibiotics as well as care for shock, associated breathing problems, or organ failure. Although the disease is contagious, transmission to family members is quite rare. If exposed to a patient who develops necrotizing fasciitis, family or household members should seek medical care if they develop a sore throat, fever, or other indication of infection, says Dr. Bisno. “There’s always a slight chance of transmission, but I wouldn’t suggest a family or household do anything other than common sense hygiene, like hand washing,” says Dr. Miller. Questions linger Although the cause of the disease is understood, experts do not know why bacteria that usually cause less serious diseases, such as strep throat, can also cause a severe infection like necrotizing fasciitis. “We wish we knew more about prevention,” admits Dr. Miller, who recommends paying careful attention to early signs of skin infections, in addition to practicing proper hygiene. Because the disease initially looks no different from a skin infection or the natural healing process of a surgical wound, misdiagnosis is common in its early stages. “Misdiagnosis is not necessarily the fault of the examining physician, because it may be very difficult to diagnose within its earliest stages,” says Dr. Bisno. He has seen cases misdiagnosed as a musculoskeletal injury, gastroenteritis, or influenza. “All of the cases were admitted in extremis within 24 to 72 hours,” says Dr. Bisno. “And, unfortunately, many died.” The speed of the infection is what can make it so deadly. Scrupulous surgical techniques are recommended to help prevent postoperative surgical site infections, according to Dr. Bisno. Although currently no vaccine exists to prevent GAS infections, research for the development of such a vaccine is ongoing. For the time being, awareness, early diagnosis, and medical treatment are the keys to surviving necrotizing fasciitis. Sidebar: Wounds should be kept clean and watched for possible signs of infection, such as redness, swelling, drainage, and pain at the wound site. A person with signs of an infected wound, especially if fever occurs, should seek medical care immediately. References:
|
|
|||
|
|
|
|
