- Gas gangrene
Gas gangrene Classification and external resources
Photograph before right leg amputation (hemipelvectomy) of a patient with gas gangrene. The right thigh is swollen, edematous and discoloured with necrotic bullae (large blisters). An impressive crepitation is already palpable. At this juncture the patient is in shock.
ICD-10 A37.0 ICD-9 040.0 DiseasesDB 31141 eMedicine med/843 emerg/211 med/394 MeSH D005738
Gas gangrene (also known as "Clostridial myonecrosis":269, and "Myonecrosis") is a bacterial infection that produces gas tissues in gangrene. It is a deadly form of gangrene usually caused by Clostridium perfringens bacteria. It is a medical emergency.
Myonecrosis is a condition of necrotic damage, specific to muscle tissue. It is often seen in infections with Clostridium perfringens or any of myriad soil-borne anaerobic bacteria. Bacteria cause myonecrosis via specific exotoxins. These microorganisms are opportunistic and, in general, enter the body via significant skin breakage. Gangrenous infection by soil-borne bacteria was common in the combat injuries of soldiers well into the 20th century, due to non-sterile field surgery and the basic nature of severe projectile wounds.
Other causes of myonecrosis include envenomation by snakes of the Bothrops genus (family Viperidae), ischemic necrosis, caused by vascular blockage (e.g., diabetes type II), tumours that block or hoard blood supply, and disseminated intravascular coagulation (DIC) or other thromboses.
Gas gangrene is caused by exotoxin-producing Clostridial species (most often Clostridium perfringens, and C. novyi but less commonly C. septicum or C. ramnosum), which are mostly found in soil but also found as normal gut flora, and other anaerobes (e.g. Bacteroides and anaerobic streptococci). The exotoxin is commonly found in C. perfringens type A strain and is known as alpha toxin. These environmental bacteria may enter the muscle through a wound and go on to proliferate in necrotic tissue and secrete powerful toxins. These toxins destroy nearby tissue, generating gas at the same time.
A gas composition of 5.9% hydrogen, 3.4% carbon dioxide, 74.5% nitrogen and 16.1% oxygen was reported in one clinical case.
Myonecrosis differs slightly from other types of necrosis. While the underlying causes are almost identical, the type of affected tissue (in particular, muscle tissue) is significantly more important for the patient's general health. Superficial necrosis is unsightly, and can lead to unattractive scarring but otherwise does not affect the patient's likelihood of survival or physical capability to the same extent. However, massive myonecrosis will likely result in the loss of movement of the entire region. If the necrotic damage is allowed to continue throughout an affected limb then often that entire limb is lost permanently.
It is often difficult to identify the extent of muscle damage, as C. perfringens may be at work in deeper fascial layers below the skin. Unlike other anaerobic infections, discharge in these infections is often not purulent (filled with pus). Instead, the discharge is often described as "sweetly putrid" or "dishwater pus" because it is much thinner than normal pus. This is due to the lysis of neutrophils, a type of white blood cell, caused by the lecithinases and other toxins released by Clostridia.
Soil-borne anaerobes are particularly well adapted to surviving harsh conditions. Often, there is a scarcity of nutrition and the presence of numerous other species competing for resources. Changes in pH and temperature are often significant also. Competing bacteria often also possess the ability to create exotoxins that assist them in competing with other microbes in their natural environment. When such bacteria are able to enter a living host, they encounter a vast supply of nutrients, warm conditions, and an abundance of water. This enables the microbes to rapidly proliferate, far in excess of the immune system's capability to defend, as prokaryotic bacteria possess a far greater capacity for multiplication than the host's immune system. The combination of bacterial load and ability to multiply is the basis for the microbes' ability to cause massive infection. Alongside such rapid proliferation is a corresponding mass-production of exotoxin that causes severe damage to local tissue in the host. One such exotoxin is produced by C. perfringens and is responsible for the disease manifestations. This exotoxin is known as alpha toxin.
Massive infection, gross injury, and depletion of the host's immune capability result in system-wide sepsis. This is partly due to the burden on the immune system, its corresponding release of inflammatory cytokines, and the distribution of bacterial toxins. Massive infection is likely to result in death from a combination of system-wide septic shock and the unintentionally damaging effects of the immune response. In animals, disability and distress caused by all of these factors markedly increases the chance of predation.
Treatment is usually debridement and excision with amputation necessary in many cases. Antibiotics alone are not effective because they do not penetrate ischaemic muscles enough to be effective. However, penicillin is given as an adjuvant treatment to surgery. In addition to surgery and antibiotics, hyperbaric oxygen therapy (HBOT) is used and acts to inhibit the growth of and kill the anaerobic C. perfringens.
Hemipelvectomy for gas gangrene.
Muscle biopsy examined under the microscope (haematoxylin-eosin stain, zoom 100×). The large white areas between the muscle fibers are due to gas formation.
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Firmicutes (low-G+C) Infectious diseases · Bacterial diseases: G+ (primarily A00–A79, 001–041, 080–109) BacilliStreptococcusαβ ClostridiaPeptostreptococcus (non-spore forming)Peptostreptococcus magnus MollicutesMycoplasmataceaeErysipelothrix rhusiopathiae (Erysipeloid)
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Look at other dictionaries:
gas gangrene — n progressive gangrene marked by impregnation of the dead and dying tissue with gas and caused by one or more toxin producing bacteria of the genus Clostridium that enter the body through wounds and proliferate in necrotic tissue * * * death and… … Medical dictionary
gas gangrene — n. a gangrene in which gas bacilli multiply in extensive, dirty wounds, producing severe pain, swollen, gas filled tissue, and toxemia … English World dictionary
gas gangrene — gas′ gan grene n. pat a gangrenous infection developing in wounds, esp. deep wounds with closed spaces, caused by bacteria that form gases in the subcutaneous tissues • Etymology: 1910–15 … From formal English to slang
gas gangrene — noun (pathology) a deadly form of gangrene usually caused by clostridium bacteria that produce toxins that cause tissue death; can be used as a bioweapon • Syn: ↑clostridial myonecrosis, ↑emphysematous gangrene, ↑emphysematous phlegmon,… … Useful english dictionary
gas gangrene — noun Date: 1914 progressive gangrene marked by impregnation of the dead and dying tissue with gas and caused by one or more toxin producing clostridia … New Collegiate Dictionary
gas gangrene — (gang grĭn) A type of gangrene that arises from dirty, lacerated wounds infected by anaerobic bacteria, especially species of Clostridium. As the bacteria grow, they release toxins and ferment carbohydrates to produce carbon dioxide and hydrogen… … Dictionary of microbiology
gas gangrene — noun rapidly spreading gangrene affecting injured tissue infected by a soil bacterium and accompanied by the evolution of foul smelling gas … English new terms dictionary
gas gangrene — death and decay of wound tissue infected by the soil bacterium Clostridium perfringens. Toxins produced by the bacterium cause putrefactive decay of connective tissue with the generation of gas. Treatment is usually by surgery … The new mediacal dictionary
gas gangrene — /ˈgæs gæŋgrin/ (say gas ganggreen) noun a gangrenous infection developing in wounds, especially deep wounds with closed spaces, due to bacteria which form gases in the subcutaneous tissues … Australian English dictionary
gas gangrene — Pathol. a gangrenous infection developing in wounds, esp. deep wounds with closed spaces, caused by bacteria that form gases in the subcutaneous tissues. [1910 15] * * * … Universalium