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Biology LibreTexts Clostridium botulinum

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    Gram stain of C. botulinum. Spores are stained pink; bacilli stain purple. Photo credit: George Lombard, Centers for Disease Control and Prevention. (Accessed through ASM Image Gallery


    • Clostridium botulinum is a large, Gram-positive endospore-forming rod
    • Like all Clostridia, C. botulinum is a strict anaerobe
    • Able to use a wide variety of sugars and other biological material as carbon and energy sources
    • Cannot grow in pHs of 4.5 or lower


    • Widely distributed in the environment, usually soil, lake sediment, and decaying vegetation


    • Food can be contaminated with endospores. When preserved through canning or otherwise stored anaerobically, the endospores germinate and produce exotoxin.
    • Endospores are often found in raw honey.  When ingested by infants who do not have established natural flora, this can lead to gastrointestinal infection.


    • Naturally occurs infrequently and sporadically
    • Most cases are intoxication through contaminated food rather than infection
    • Infection can occur in infants through ingestion of endospores

    Clinical Disease

    • Toxin inhibits acetylcholine release leading to flaccid paralysis (cannot contract muscles).
    • Early symptoms appear within about a day and include weakness, dizziness and dryness of the mouth.  Other gastrointestinal symptoms may be present.
    • In later disease, it becomes difficult to speak and swallow, muscle weakness increases, and eventually the diaphragm can be paralyzed
    • Primary treatment is antitoxin and supportive therapy
    • Without treatment, mortality rate is >60%, but with treatment it is ~4-20%

    Primary Virulence Factors

    • The only virulence factor is botulinum toxin (link to info in textbook)

    Additional information: Clostridium botulinum is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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