Botulism
German physicians first identified botulism in the late 18th century when patients developed an often fatal disease after eating spoiled sausage. Five distinct clinical syndromes are now recognized: food-borne botulism, infant botulism, wound botulism, adult intestinal colonization, and iatrogenic botulism. Food-borne botulism, the best-known form, results from ingestion of preformed toxin in improperly preserved home-canned vegetables, fish, or meats. In the last few decades, noncanned foods have also been reported to cause food-borne botulism. Examples include fresh garlic in olive oil, sautéed onions, beef or turkey pot pie, baked potatoes, potato salad, smoked whitefish, turkey loaf, and turkey stuffing.
Mechanism of toxicity
Botulism is caused by a heat-labile neurotoxin (botulin) produced by the bacterium Clostridium botulinum. Different strains of the bacterium produce seven distinct exotoxins: A, B, C, D, E, F, and G; types A, B, and E are most frequently involved in human disease. Botulin toxin irreversibly binds to cholinergic nerve terminals and prevents acetylcholine release from the axon. Severe muscle weakness results, and death is caused by respiratory failure. Symptoms may be slow in onset but are sometimes rapidly progressive. The toxin does not cross the blood-brain barrier.
Botulinum spores are ubiquitous in nature, and except in infants (and in rare situations adults), the ingestion of spores is harmless. However, in an anaerobic environment with a pH of 4.6–7, the spores germinate and produce botulinum toxin. The spores are relatively heat-stable but can be destroyed by pressure cooking at a temperature of at least 120°C (250°F) for 30 minutes. The toxin is heat-labile and can be destroyed by boiling at 100°C (212°F) for 10 minutes or heating at 80°C (176°F) for 20 minutes. Nitrites added to meats and canned foods inhibit the growth of clostridia.
Toxic dose. Botulin toxin is extremely potent; as little as one taste of botulinum-contaminated food (approximately 0.05 mcg of toxin) may be fatal.
Clinical presentation
Classic food-borne botulism
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