are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages. The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle. Clostridium Endospores have a distinct bowling pin or bottle shape, distinguishing them from other bacterial endospores, which are usually ovoid in shape. The Schaeffer-Fulton stain (0.5% malachite green in water) can be used to distinguish endospores of Bacillus and Clostridium from other microorganisms. Clostridium can be differentiated from the also Endspore forming genus Bacillus by its obligate anaerobic growth, the shape of endospores and the lack of catalase. Species of Desulfotomaculum form similar endospores and can be distinguished by their requirement for sulfur. Glycolysis and fermentation of pyruvic acid by Clostridia yield the end products butyric acid, butanol, acetone, isopropanol, and carbon dioxide. There is a commercially available polymerase chain reaction (PCR) test kit (Bactotype) for the detection of C. perfringens and other pathogenic bacteria. Biology and pathogenesis Clostridium species are readily found inhabiting soils and intestinal tracts. Clostridium species are also a normal inhabitant of the healthy lower reproductive tract of females. The main species responsible for disease in humans are: Clostridium botulinum can produce botulinum toxin in food or wounds and can cause botulism. This same toxin is known as Botox and is used in cosmetic surgery to paralyze facial muscles to reduce the signs of aging; it also has numerous other therapeutic uses. Clostridium perfringens causes a wide range of symptoms, from food poisoning to cellulitis, fasciitis, necrotic enteritis and gas gangrene. Clostridium tetani causes tetanus. Several more pathogens were previously described in Clostridium, but have been moved to other genera with additional research. Clostridium difficile, now placed in Clostridioides. Clostridium histolyticum, now placed in Hathewaya. Clostridium sordellii, now placed in Paeniclostridium, can cause a fatal infection in exceptionally rare cases after medical abortions. Treatment In general, the treatment of clostridial infection is high-dose penicillin G, to which the organism has remained susceptible. Clostridium welchii and Clostridium tetani respond to sulfonamides. Clostridia are also susceptible to tetracyclines, carbapenems (imipenem), metronidazole, vancomycin, and chloramphenicol. The vegetative cells of clostridia are heat-labile and are killed by short heating at temperatures above 72–75 °C. The thermal destruction of Clostridium spores requires higher temperatures (above 121.1 °C, for example in an autoclave) and longer cooking times (20 min, with a