Gas gangrene

Gas gangrene (also known as clostridial myonecrosis and myonecrosis) is a bacterial infection that produces tissue gas in gangrene. This deadly form of gangrene usually is caused by Clostridium perfringens bacteria. About 1,000 cases of gas gangrene are reported yearly in the United States.Gas gangrene can cause myonecrosis (muscle tissue death), gas production, and sepsis. Progression to toxemia and shock is often very rapid. It can easily be noticed by the large, blackened sores that form, as well as a degree of loud and distinctive crepitus caused by gas escaping the necrotic tissue.Gas gangrene is caused by exotoxin-producing Clostridium species (most often C. 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. This alpha toxin is a lethal toxin and also known as phospholipase C (lecithinase). It increases vascular permeability and produces necrotizing activity. 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.Treatment is usually debridement and excision, with amputation necessary in many cases. Water-soluble antibiotics (such as penicillin) alone are not effective because they do not penetrate ischaemic muscles sufficiently to be effective. Penicillin is effective against C. perfringens. When gas gangrene occurs in such regions as the abdominal cavity, the patient can be treated in a hyperbaric chamber. which contains a pressurized oxygen-rich atmosphere. The oxygen saturates the infected tissues and thereby prevents the growth of the obligately anaerobic clostridia. The growth of C. perfringens is inhibited when the availability of oxygen is equivalent to a partial pressure of around 9–10 kPa (compare to 4–5 kPa in venous blood under normal conditions, with 11–13 kPa in arteries and 21 kPa in air at sea level), so if the treatment is started early, this condition can mostly be cured.Hemipelvectomy for gas gangreneMuscle biopsy examined under the microscope (haematoxylin-eosin stain, zoom 100×): the large white areas between the muscle fibers are due to gas formation.Gram stain of a muscle biopsy showing Gram-positive, rod-shaped, anaerobic, spore-forming bacteria in the infected muscle tissue: The result is highly compatible with an infection with C. perfringens.Gas gangrene of the shoulder.