Most common toxin is hyaluronidase Clostridium are gram positive spore forming rods. - The spores enable these organisms to survive in adverse conditions e.g. in soil and dust and on skin. - Most species are obligate anaerobes i.e. their spores do not germinate and growth does not normally proceed unless a suitably low redox potential (Eb) exists. Clostridium perfringens Clostridium perfringens cause two impoant diseases:? Gas gangrene "Clostridium perfringens is the commonest cause of gas gangrene". The disease is characterized by rapidly spreading edema, myositis and necrosis of tissues, gas production and profound toxemia. Clostridium perfringens produces several toxins and other substance which have a role in the pathogenesis of gas gangrene. "a Toxin a phospholipase lecithinase" is generally considered to he the most impoant toxin in the pathogenesis of gas gangrene. -It is produced by all types of clostridium perfringens and most abundantly by type "A" strains. - It is the most impoant toxin biologically and is responsible .for profound toxemia of the gas gangrene. - It is a "phospholipase". Other factors which also have a role in virulence:- Hyaluronida.ve It breaks down intercellular cement substance and promotes the spread of the infection along the tissue planes Collagenases and other proteinases They break down tissues and viually liquefy muscles. Clostridium food poisoning:- Clostridium perfringens is an impoant cause of food poisoning. The .food poisoning is caused due to ingestion of spores. The spores of the clostridium perfringens strains that cause food poisoning are heat resistant. -The unique feature of spores produced by food poisoning strains of clostridium perfringens is that they are heat resistant that can survive boiling for several hours. Remember - Only those strains of clostridia which are associated with food poisoning produce heat resistant spores Where as - The classic strains of this species do not have heat resistant spores. These spores are inactivated within few minutes by boiling. Typical, food poisoning strains of clostridium perfringens occur as carrier state. These strains also occur in animals thus meat is often contaminated with heat resistant spores. The vehicle of infection is usually a precooked meat food that has been allowed to stand at a temperature. The heat resistance of the spores ensures their survival in cooking. - During the cooling period they germinate in the anaerobic environment produced by the cooked meat and multiply. - Anyone who eats this meat will consume the equivalent of cooked meat broth culture of the organisms. - Large numbers of clostridia are thus consumed which may pass unharmed by the gastric acid due to high protein in the meat and reach the intestines where they produce the enterotoxin. - After an incubation period of 8-24 hours abdominal pain diarrhoea set in. Naegeler reaction ft is used to detect alpha toxin which is a phospholipase (lecithinase C) - Lecithinase or phospholipase in the presence of Ca++ and Mg' ions splits lecithin into phosphorylcholine and diacylglycerol. This reaction is seen as an "opalescence" in serum or egg yolk media. Procedure CI perfringens is grown on a plate where one half of the plate is covered with alpha antitoxin. The half poion of the plate without the antitoxin produces opalescene. - Pho.spholipase or a toxin splits the lecithin into phosphorylcholine and diacyl glycerol. Which is seen as opalescnee. The other half of the plate where alpha antitoxin is present does not demonstrate opalescence because here alpha toxin or phospholipase is neutralized by the toxin.