What is botulism?

Updated: Feb 15, 2019
  • Author: Kirk M Chan-Tack, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Botulism is an acute neurologic disorder that causes potentially life-threatening neuroparalysis due to a neurotoxin produced by Clostridium botulinum. The toxin binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions. Toxin binding blocks acetylcholine release, resulting in weakness, flaccid paralysis, and, often, respiratory arrest. Cure occurs following sprouting of new nerve terminals.

The 3 main clinical presentations of botulism include infant botulism (IB), foodborne botulism (FBB), and wound botulism (WB). Additionally, because of the potency of the toxin, the possibility of botulism as a bioterrorism agent or biological weapon is a great concern. [1] For more information, see CBRNE – Botulism.

Infant botulism is caused by ingested C botulinum spores that germinate in the intestine and produce toxin. These spores typically come from bee honey or the environment. Most infants fully recover with supportive treatment; the attributed infant mortality rate is less than 1%. Improperly canned or home-prepared foods are common sources of the toxin that can result in foodborne botulism. Wound botulism results from contamination of a wound with toxin-producing C botulinum. Foodborne botulism and wound botulism occur predominantly in adults and are the focus of this article.

C botulinum is an anaerobic gram-positive rod that survives in soil and marine sediment by forming spores. Under anaerobic conditions that permit germination, it synthesizes and releases a potent exotoxin. Microbiologically, the organism stains gram-positive in cultures less than 18 hours old. The organism may stain gram-negative after 18 hours of incubation, potentially complicating attempts at diagnosis. On a molecular weight basis, botulinum toxins are the most potent toxins known.

Eight antigenically distinct C botulinum toxins are known, including A, B, C (alpha), C (beta), D, E, F, and G. Each strain of C botulinum can produce only a single toxin type. Types A, B, E, and, rarely, F cause human disease. Toxins A and B are the most potent, and the consumption of small amounts of food contaminated with these types has resulted in full-blown disease. During the last 20 years, toxin A has been the most common cause of foodborne outbreaks; toxins B and E follow in frequency. In 15% of C botulinum infection outbreaks, the toxin type is not determined. Toxins C and D cause disease in various animals. Type G toxin has been associated with sudden death but not with neuroparalytic illness. It was isolated from autopsy material from 5 patients in Switzerland in 1977.

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