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Clostridium botulinum

Photomicrograph of listeria monocytogenes

Electron micrograph of Clostridium botulinum

Pathogens & Protocols

Why it's a Threat

Clostridium botulinum and some strains of C. butyricum and C. baratii produce botulinum toxin which causes botulism, a rare (less than 150 cases in the US per year) but potentially fatal illness that causes paralysis.  There are four naturally occurring types of botulism.

  1. Foodborne botulism is caused by eating contaminated foods in which C. botulinum has grown and produced botulinum toxin.
  2. Wound botulism is caused by the growth of C. botulinum in a wound
  3. Infant botulism is caused by the growth of C. botulinum or in the intestinal tract of infants
  4. Adult colonization is caused by the growth of C. botulinum in the intestinal tract of adults.

Death occurs from respiratory failure in all four types of botulism. Foodborne botulism is a public health emergency because many people can be poisoned by eating the contaminated food. Botulinum toxin also is considered a potential bioterrorism weapon.


Gram-positive, anaerobic, straight to slightly curved rods (single or pairs) strain variable from 0.5 to 2.5 microns wide and 1.6 to 22 microns long; usually motile and forms oval subterminal spores. There are seven serotypes (A-G).  The bacteria require specific environmental conditions for growth and toxin production including absence of oxygen, and low levels of acid, sugar, and salt.


Bacterial spores can be found in raw vegetables, intestinal tract of animals, soil, non-treated water sources, and occasionally dust.

  • Foodborne botulism cases are usually caused by home-canned foods but large outbreaks have occurred with commercially produced foods and in restaurants.
  • Most Wound botulism cases are associated with black-tar heroin injection but rare cases have occurred from soil contamination of compound fractures and other serious deep wounds.
  • Spores have been identified in honey and so ingestion of honey was named by the American Academy of Pediatrics as a risk for Infant botulism.


  • Follow strict hygienic procedures to reduce contamination of home-preserved foods and carefully follow instructions on safe home canning including the use of pressure canners/cookers.  
  • Boiling home-preserved foods for 10 minutes before eating will destroy the toxin.
  • Wound botulism can be prevented by promptly seeking medical care for infected wounds and by not using injectable street drugs.
  • Honey can contain the bacteria that causes Infant botulism, so children younger than 12 months should not be fed honey.


The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a breathing machine (ventilator) for weeks or months. The patient may require rehabilitation therapy after leaving the hospital.

Treatment with botulism antitoxin removes toxin circulating in the blood but it does not reverse the symptoms that were present before treatment. Antitoxin to treat all botulism types except Infant botulism is available only through CDC.  An antitoxin specific for treating Infant botulism is available through the California Department of Public Health.

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