Clostridium botulinum

Clostridium botulinum is spore-forming bacteria that produce a neurotoxin. The spores are heat-resistant and can survive in foods that are incorrectly or minimally processed. Seven types (A, B, C, D, E, F and G) of botulism are recognized. Types A, B, E and F cause human botulism. Types C and D cause most cases of botulism in animals. Although type G has been isolated from soil in Argentina, no outbreaks involving it have been recognized.

Food borne botulism (as distinct from wound botulism and infant botulism) is a severe food poisoning caused by the eating foods containing the potent neurotoxin formed during growth of the bacteria. This toxin is heat labile but can be destroyed if heated at 80°C for 10 minutes or longer. The incidence of the disease is low, but the disease is of considerable concern because of its high mortality rate when not treated immediately and properly. Most outbreaks are associated with inadequately processed, home-canned foods, but sometimes-commercial foods are involved in outbreaks. Sausages, meat products, canned vegetables and seafood products are most commonly involved.

The bacteria and its spores are common in nature. They exist in cultivated and forest soils, bottom sediments of streams, lakes, and coastal waters, and in the intestinal tracts of fish and mammals, and in the gills and viscera of crabs and other shellfish. A very small amount (a few nanograms) of toxin can cause illness

Four types of botulism are recognized: food borne, infant, wound, and a form of botulism whose classification is as yet undetermined. Certain foods have been reported as sources of spores in cases of infant botulism and the undetermined category; wound botulism is not related to foods.

Food borne botulism (or food borne intoxication) is caused by consuming foods containing the neurotoxin produced by C. botulinum . Symptoms occur 18 to 36 hours after ingestion of the food with the toxin, but cases have varied from 4 hours to 8 days. Early signs consist of marked lassitude, weakness and vertigo, followed by double vision and progressive difficulty in speaking and swallowing. Difficulty in breathing, weakness of other muscles, abdominal distension, and constipation may also be common symptoms

Foods involved in botulism vary with food preservation and eating habits in different regions. Any food that allows bacteria growth and toxin production, and when processed allows spore survival, but is not subsequently heated before consumption can be associated with botulism. Any food that is not very acidic (pH above 4.6) will support growth and toxin production by C. botulinum .

Botulinal toxin has been found in canned corn, peppers, green beans, soups, beets, asparagus, mushrooms, ripe olives, spinach, tuna fish, chicken and chicken livers and liver pate, and luncheon meats, ham, sausage, stuffed eggplant, lobster, and smoked and salted fish.

Botulinum toxin causes flaccid paralysis that progresses symmetrically downward, starting with the eyes and face, to the throat, chest and extremities. When the diaphragm and chest muscles are involved, respiration is inhibited and death from asphyxia occurs. Treatment for food borne botulism includes giving botulinal antitoxin and intensive supportive.

Determining sources during an outbreak is based on identifying toxin in the involved food. Culturing all suspect food in an enrichment medium to detect and isolate the causative organism, which takes 7 days, follows this analysis.

Infant botulism , affects babies under 12 months of age. This is caused by the eating C. botulinum spores, which colonize and produce toxin in the infant's intestinal tract (intestinal toxaemia botulism Honey is the one dietary reservoir of C. botulinum spores linked to infant botulism. Symptoms consist of constipation occur after a period of normal development. This is followed by poor feeding, lethargy, weakness, pooled oral secretions, and wail or altered cry. Loss of head control is striking. Treatment is primarily supportive care. Antibiotics are not recommended. Demonstrating botulinal toxins and the bacteria in the infants' stools proves infant botulism.

Wound botulism is the rarest form of botulism. Foods are not involved in this type of botulism. The illness occurs when C. botulinum by itself or with other germs infects a wound and produces toxins.

Undetermined category of botulism involves adult cases in which a specific food or wound source cannot be identified..

Reference:

An incident of food borne botulism MMWR 44(11):1995 Mar 24 .

Botulism type B outbreak associated with eggplant in oil MMWR 44(2):1995 Jan 20 .

The botulism outbreak with salted fish MMWR 36(49):1987 Dec 18 .