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Chapter: Microbiology and Immunology: Bacteriology: Clostridium

Epidemiology - Clostridium botulinum

Human botulism is found worldwide.


Human botulism is found worldwide.


C. botulinum is ubiquitous. It is found in soil and water world-wide. Spores of C. botulinum type A or B are distributed widely in the soil and have been found throughout the world.

 Geographical distribution

·             C. botulinum types A, B, E, and rarely F and G toxins causehuman disease. Types C and D cause avian and nonhuman mammalian disease. Infant botulism is more common than food-borne botulism. Food-borne botulism is caused by C. botulinum types A, B, and F; very rarely E types.


·            Wound botulism is very rare and is caused by C. botulinum type A strains.


 Reservoir, source, and transmission of infection

botulinum spores are responsible for causing botulism:

·           Preserved food especially homemade, canned meat and meat products in Europe, canned vegetables in America, and preserved fish in Japan, contaminated with preformed toxin are the main sources of infections for food-borne botulism.

·           Honey and other food contaminated with spores of bacte-ria are the sources of infection for infant botulism.

·           Soil and water heavily contaminated with spores are sources of infection for wound botulism.

Transmission of infection: Botulism is transmitted infollowing ways:

·    Wound botulism occurs as a result of contamination of wound with spore-forming C. botulinum. The condition occurs in (a) people with traumatic injury involving contamination with soil, (b) in people who chronically abuse intravenous drugs (e.g., black tar heroin), and (c) in women after cesarean delivery (very rare). The condition can also occur even after antibiotics are administered to prevent wound infection.


·    Food-borne botulism results from the ingestion of pre-formed neurotoxins in the food. Consumption of food contaminated with even very small amounts of these toxins has resulted in full-blown disease. During the last 20 years, toxin A has been the most frequent cause of food-borne out-breaks; toxins B and E follow in frequency.


High-risk foods include home-canned or home-processed low-acid fruits and vegetables; fish and fish products; and condiments, such as relish and chili peppers. Commercially prepared foods and improperly handled fresh foods may occasionally cause outbreaks of botulism

·           Infant botulism occurs following ingestion of C. botulinum spores present in infant food such as honey. The spores then germinate to toxin-producing vegetative form that colonize the infant gut. Toxin that is produced in and absorbed from the gut causes the clinical disease.

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