Necrotizing Fasciitis
Necrotizing Fasciitis
Disease History, Characteristics, and Transmission
Introduction
Necrotizing fasciitis is a rare, and often fatal, infection by the bacterium Streptococcus pyogenes, also known as group-A streptococcus or GAS. Varieties of this bacterium also cause a wide range of other diseases, including strep throat, impetigo, cellulitis, erysipelas, scarlet fever, rheumatic fever, and more. To necrotize tissue is to kill it, and the word fasciitis signifies inflammation of the fascia, which are the thin sheaths of fibrous connective tissue that cover the muscles and other organs. In necrotizing fasciitis, group-A streptococci infect the deeper layers of the skin and the fascia in the tissue underneath the skin. Although this disease has often been referred to in the press as being caused by “flesh-eating bacteria,” GAS is not flesh-eating; that is, it does not actually eat away the flesh of victims of necrotizing fasciitis. Rather, GAS releases toxins that cause the body's own immune system to dissolve certain tissues. Necrotizing fasciitis first became popularly known in the 1990s. There was fear that it would become widespread, but it has remained rare. Necrotizing fasciitis is only one form of invasive group-A streptococcus infection. Other closely related forms include streptococcal toxic-shock syndrome (multi-organ infection) and bacteremia (infection of the blood).
Disease History, Characteristics, and Transmission
The German-Austrian surgeon Christian Theodor Billroth (1829–1894) first described the streptococci bacterium. Billroth discovered Streptococcus pyogenes growing in infected wounds. The streptococci are gram-positive bacteria that tend to clump in pairs or chains and are classed into two basic types based on their ability to cause partial or complete hemolysis (breakdown of blood cells). Group A streptococci, which cause complete hemolysis, are further subdivided into a series of alphabetically labeled groups called Lancefield groups. In the 1930s, Rebecca Lancefield (1895–1981) defined the Lancefield groups using standard laboratory tests. She also showed that a protein in the GAS cell wall, M protein, is important to this bacterium's disease-causing power. Varying types of M protein can be used to distinguish over 120 different varieties of S. pyogenes, including those that cause necrotizing fasciitis.
Shifts in the M proteins and other substances produced by various strains of S. pyogenes are caused by genetic mutations and by genetic alterations caused by viruses (which can change the DNA of bacteria and other cells). Because of these changes, the virulence (tendency to cause disease) of various S. pyogenes strains waxes and wanes over time. During World War II (1939–1945), for example, there were reports of GAS bacteria causing toxic shock and destruction of tissue. These reports then abated until the late 1980s, when clusters of such infections began appearing in Australia, New Zealand, Scandinavia, and the central United States. A survey of four American states by the U.S. Centers for Disease Control and Prevention (CDC) conducted from 1989 to 1991 estimated that 10,000–15,000 invasive group A streptococcus infections were occurring in the U.S. each year. British tabloid writers coined the phrase “flesh-eating bacteria” to describe the new type of GAS infection. Necrotizing fasciitis has continued to occur at a more or less steady rate in the years since, neither disappearing nor becoming epidemic.
There are several types of life-threatening, invasive streptococcus A infections. Necrotizing fasciitis is a deep-seated infection of the tissues beneath the outer skin that destroys fascia and fat but may or may not destroy muscle and skin. It can be caused not only by S. pyogenes but, less commonly, by Clostridium perfringens or C. septicum. Necrotizing fasciitis may be caused by a blend of organisms in patients with diabetes or open wounds contaminated with fecal matter. An early term for the condition was “streptococcal gangrene.” Infections can begin at the site of a major or even invisible breakage of the skin. Typically, within 24 hours a lesion or sore spot appears at the wound site that is red, hot, and painful to the touch. There may also be fever. In the next 24–48 hours, the lesion becomes purple, violet, or blue, and blisters appear. Influenzalike symptoms occur in about 20% of cases, with symptoms including nausea, diarrhea, confusion, weakness, and tiredness. In three to four days gangrene may appear, with the entire limb, in some cases, appearing necrotic. The disease can cause death through shock, kidney failure, and respiratory arrest.
S. pyogenes is transmitted by direct contact or via airborne saliva droplets released by sneezing or coughing. Necrotizing fasciitis occurs when an appropriate strain of S. pyogenes enters a break in the skin. The break may be a large wound or a pinprick; in half of all cases, the break through which the pathogen entered cannot be identified.
Scope and Distribution
Severe invasive group-A streptococcal disease, including necrotizing fasciitis, is primarily found in Europe and North America. In 2004, 3,833 cases of severe group A streptococcal disease were reported to the CDC.
Treatment and Prevention
Necrotizing fasciitis is treated with antibiotics, including penicillin, erythromycin, and clindamycin. In some cases, treatment may require amputation or other surgery to remove damaged tissue. Prompt care is essential. Without antibiotics, the death rate for invasive group-A streptococcus infection, including necrotizing fasciitis, is nearly 100%. Even with treatment the death rate is estimated by various experts at 25% to as much as 70%. In the 1990s, when public concern over this disease was at its height, Dr. Vincent Fischetti of Rockefeller University in New York advised the public that “If you see a rapidly progressing reddening area that is hot and quite sore to the touch and if you are running a fever, I would go to the doctor very quickly.”
WORDS TO KNOW
CLINICAL TRIALS: According to the National Institutes of Health, a clinical trial is “a research study to answer specific questions about vaccines or new therapies or new ways of using known treatments.” These studies allow researchers to determine whether new drugs or treatments are safe and effective. When conducted carefully, clinical trials can provide fast and safe answers to these questions.
FASCIA: Fascia is a type of connective tissue made up of a network of fibers. It is best thought of as being the packing material of the body. Fascia surrounds muscles, bones, and joints and lies between the layers of skin. It functions to hold these structures together, protecting these structures and defining the shape of the body. When surrounding a muscle, fascia helps prevent a contracting muscle from catching or causing excessive friction on neighboring muscles.
GANGRENE: Gangrene is the destruction of body tissue by a bacteria called Clostridium perfringens, or a combination of streptococci and staphylococci bacteria. C. perfringens is found widespread in soil and the intestinal tracts of humans and animals. It becomes dangerous only when its spores germinate, producing toxins and destructive enzymes, and germination occurs only in an anaerobic environment (one almost totally devoid of oxygen). While gangrene can develop in any part of the body, it is most common in fingers, toes, hands, feet, arms, and legs, the parts of the body most susceptible to restricted blood flow. Even a slight injury in such an area is at high risk of causing gangrene. Early treatment with antibiotics, such as penicillin, and surgery to remove the dead tissue will often reduce the need for amputation. If left untreated, gangrene results in amputation or death.
HEMOLYSIS: The destruction of blood cells, an abnormal rate of which may lead to lowered levels of these cells. For example, Hemolytic anemia is caused by destruction of red blood cells at a rate faster than which they can be produced.
M PROTEIN: M protein is an antibody found in unusually large amounts in the blood or urine of patients with multiple myeloma, a form of cancer that arises in the white blood cells that produce antibodies.
MUTATION: A mutation is a change in an organism's DNA that occurs over time and may render it less sensitive to drugs which are used against it.
NECROTIC: Necrotic tissue is dead tissue in an otherwise living body. Tissue death is called necrosis.
STREPTOCOCCUS: A genus of bacteria that includes species such as Streptococci pyogenes a species of bacteria that causes strep throat.
IN CONTEXT: TRENDS AND STATISTICS
The Division of Bacterial and Mycotic Diseases at Centers for Disease Control and Prevention (CDC) states that About 9,400 cases of invasive GAS disease occurred in the United States in 1999. Of these, about 300 were streptococcal toxic shock syndrome (STSS) and 600 were necrotizing fasciitis. In contrast, there are several million cases of strep throat and impetigo each year.
SOURCE: Centers for Disease Control and Prevention (CDC), Coordinating Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases
Impacts and Issues
Public consciousness of invasive group A streptococcal disease, including necrotizing fasciitis, has been out of proportion to the number of deaths it causes as compared to many other diseases and behaviors. Undoubtedly, one reason for this is the dramatic nature of the disease. A bacterial infection that “eats flesh” and has a 25–70% fatality rate even with the best medical care is certainly attention-getting. In addition, there have been a number of well-publicized deaths from the disease, including leading British economist David Walton (1963–2006), who died within 24 hours of diagnosis.
A vaccine for group-A streptococcus is being investigated, but remains elusive. According to the World Health Organization (WHO), clinical trials—experiments in human volunteers designed to test the vaccine's effectiveness and safety—are under way, but will probably take years to complete.
IN CONTEXT: REAL-WORLD RISKS
The Division of Bacterial and Mycotic Diseases at Centers for Disease Control and Prevention (CDC) states that “two of the most severe, but least common, forms of invasive GAS disease are necrotizing fasciitis and streptococcal toxic shock syndrome. Necrotizing fasciitis (occasionally described by the media as ‘the flesh-eating bacteria’) destroys muscles, fat, and skin tissue. Streptococcal toxic shock syndrome (STSS) causes blood pressure to drop rapidly and organs (e.g., kidney, liver, lungs) to fail. STSS is not the same as the ‘toxic shock syndrome’ frequently associated with tampon usage. About 20% of patients with necrotizing fasciitis, and more than half with STSS, die. About 10%–15% of patients with other forms of invasive group A streptococcal disease die.”
SOURCE: Centers for Disease Control and Prevention (CDC), Coordinating Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases.
See AlsoImpetigo; Puerperal Fever; Scarlet Fever; Streptococcal Infections, Group A; Streptococcal Infections, Group B.
BIBLIOGRAPHY
Books
ICON Health Publications. Necrotizing Fasciitis. San Diego, CA: ICON Health Publications, 2004.
Periodicals
Factor, Stephanie H., et al. “Invasive Group A Streptococcal Disease: Risk Factors for Adults.” Emerging Infectious Diseases 9 (2003): 970–977.
Factor, Stephanie H., et al. “Risk Factors for Pediatric Invasive Group A Streptococcal Disease.” Emerging Infectious Diseases 11 (2005): 1062–1066.
Kolata, Gina. “A Dangerous Form of Strep Stirs Concern in Resurgence.” New York Times (June 8, 1994).
Musher, Daniel M., et al. “Trends in Bacteremic Infection Due to Streptococcus pyogenes (Group A Streptococcus), 1986–1995.” Emerging Infectious Diseases 2 (1996): 54–56.
Stevens, Dennis L. “Streptococcal Toxic-Shock Syndrome: Spectrum of Disease, Pathogenesis, and New Concepts in Treatment.” Emerging Infectious Diseases 1 (1995): 69–76.
Web Sites
National Institute of Allergy and Infectious Diseases. “Group A Streptococcal Infections.” November 2005. <http://www.niaid.nih.gov/factsheets/strep.htm> (accessed February 14, 2007).
National Necrotizing Fasciitis Foundation. “Home Page.” January 28, 2007. <http://www.nnff.org/> (accessed February 14, 2007).