Pathogen Safety Data Sheets: Infectious Substances – Clostridium botulinum



NAME: Clostridium botulinum.

SYNONYM OR CROSS REFERENCE: BotulismFootnote 1-3, allantiasisFootnote 2, and botulinum toxinFootnote 4.

CHARACTERISTICS: A gram-positive (at least in early stage of growth), anaerobic, rod- shapedFootnote 3, spore-forming bacillusFootnote 1-3. Seven types of C. botulinum toxins exist (A-F)Footnote 1Footnote 2Footnote 5.Types A, B, E, and rarely F can cause human botulism. Strains consistent with type G were assigned to C. argentinense in 1993. Botulinum neurotoxin is produced when, under anaerobic conditions, C. botulinum spores germinateFootnote 3Footnote 5Footnote 6. In addition to C. botulinum, C. argentinense (formerly C. botulinum type G), C. butyricum, and C. baratii can also produce botulinum neurotoxin.

C. botulinum (botulinum toxin) is defined as a biothreat level A organism by the Centers for Disease Control and PreventionFootnote 7. Category A organisms are considered to pose the greatest threat to national security.


PATHOGENICITY: Rare but serious paralytic diseaseFootnote 1Footnote 6, caused by a neurotoxin formed during the growth of the spore-forming bacterium C. botulinum (or rarely, C. argentinense, C. butyricum, or C. baratii )Footnote 3Footnote 5. This neurotoxin binds to the neuromuscular junction and blocks excitatory synaptic transmission by inhibiting acetylcholine releaseFootnote 2Footnote 8, causing (flaccid) paralysisFootnote 1Footnote 5Footnote 6, and sometimes fatal respiratory failureFootnote 1Footnote 2Footnote 5Footnote 8. The fatality rate of botulism is 5 to 10%Footnote 8.

Food-borne botulism: The classic form of botulism is caused by the ingestion of preformed toxin in contaminated foodFootnote 1Footnote 2Footnote 5Footnote 8. Symptoms include double vision, drooping eyelids (ptosis), slurred speech, difficulty swallowing and muscle weakness that is symmetric and descends through the body (first shoulders are affected, then upper arms, lower arms, thighs, calves, etc.)Footnote 1. Death is usually due to respiratory failureFootnote 1Footnote 2Footnote 6Footnote 8 and may occur as soon as 24 hours after onset of symptomsFootnote 8.

Wound botulism: Occurs by contamination of a wound with spores from neurotoxin-producing Clostridium species in the environment and subsequent germination of these spores and production of toxin in the anaerobic milieu of an abscessFootnote 1Footnote 5Footnote 4. The toxin is released into the bloodstreamFootnote 1Footnote 6 and symptoms may take up to 2 weeks to appearFootnote 4.

Intestinal (infant) botulism: Results almost exclusively from spore ingestion and subsequent growth and toxin production in the intestineFootnote 1Footnote 2Footnote 5, affecting infants under 1 year oldFootnote 1Footnote 5Footnote 9. The first clinical sign is usually constipationFootnote 1Footnote 2, but this disease has a wide spectrum of clinical severity, ranging from mild illness with gradual onset, to sudden infant death due to respiratory failureFootnote 1Footnote 2. With appropriate intensive care, almost 100% of infants with botulism make a full recoveryFootnote 5. Infants with botulism are lethargic, feed poorly, have a weakened cry, exhibit ptosis, and floppy neck, and may progress to generalised flaccidity and respiratory compromiseFootnote 2Footnote 4.

Adult infectious botulism: RareFootnote 5. Caused by the intestinal colonization of C. botulinum / other neurotoxin producing species, followed by in vivo toxin production in a manner similar to infant botulismFootnote 1Footnote 2Footnote 5. Patients often have a history of immunocompromise, abdominal surgery, bowel disease, or recent antibiotic therapy.

Inhalational botulism: Is not a naturally occurring diseaseFootnote 5, but has occurred in laboratory workers due to inhalation of aerosolized toxinFootnote 1. Inhalational botulism leads to neurological symptoms similar to those of food-borne botulism, but with a longer incubation periodFootnote 5Footnote 6.

Iatrogenic botulism: Side effects resulting from the therapeutic intramuscular injection of Botox (purified, diluted A neurotoxin)Footnote 5. Characterized by clinical weakness and electrophysiological abnormalitiesFootnote 10Footnote 11.

EPIDEMIOLOGY: Sporadic. Family and general outbreaks occur worldwide in association with food products prepared or preserved by means that do not destroy spores and permit the formation of toxinFootnote 1Footnote 2Footnote 5.

HOST RANGE: Humans, and various animals, e.g., fowl, fish, cows, dogs, and minksFootnote 1Footnote 2.

INFECTIOUS DOSE: Cells/spores are not normally toxic for healthy adultsFootnote 2. Botulinum toxin is the most potent toxin known, with an estimated oral or injected toxic dose (serotype A) of 0.001 μg/kg body weight, and an estimated lethal dose by inhalation exposure in humans of approximately 0.07 μg/kg body weightFootnote 5Footnote 6. Type A toxin is more potent than types B and E and causes the longest lasting diseaseFootnote 9.

MODE OF TRANSMISSION: Food borne botulism: Ingestion of contaminated food containing toxinFootnote 1Footnote 2Footnote 5. Infection is commonly associated with commercially processed foods that had undergone poor processing, storage, and improper preservationFootnote 12.

Wound botulism: Contamination of wounds with spores of neurotoxin producing Clostridium speciesFootnote 1Footnote 2Footnote 5 and is seen almost exclusively in injection drug users, particularly those who partake in injection of black-tar heroin into skin tissueFootnote 5Footnote 13.

Intestinal (infant) botulism: Ingestion of spores. Sources include honey and infant milk powderFootnote 1Footnote 5Footnote 9.

Adult infectious botulism: Ingestion of clostridial spores, rather than toxin, which then colonize the gut to produce their neurotoxin directly in the gutFootnote 1Footnote 5Footnote 9.

Iatrogenic botulism: Side effect of injection of purified toxinFootnote 5.

Inhalational botulism: Occurs due to absorption of botulinum toxin by the mucous membrane of the noseFootnote 5Footnote 6.

INCUBATION PERIOD: The shorter the incubation period, the more severe the disease and the higher the case fatality rateFootnote 1.

Food-borne botulism: Usually 12 to 72 hrs after ingestion of toxin, depending on the doseFootnote 9.

Wound botulism: The median period is 7 daysFootnote 9.

Adult infectious botulism: UnknownFootnote 1.

Intestinal botulism: UnknownFootnote 1.

Inhalational botulism: Not well defined, but it is longer than for food borne botulismFootnote 1Footnote 6, and is estimated at 12-80 hoursFootnote 14.

COMMUNICABILITY: No evidence of person-to-person transmissionFootnote 1Footnote 5.


RESERVOIR: Spores are found in soil, aquatic sediments, the intestinal tract of birds, animals and fish, and agricultural products, including honey and vegetablesFootnote 1Footnote 2Footnote 13.

ZOONOSIS: No epidemiological relationship between human and animal botulism has been establishedFootnote 2.



DRUG SUSCEPTIBILITY: Susceptible to penicillin, metronidazole, clindamycin, cephalothin, cefoxitin, cefotaxime, chloramphenicol, tetracycline, erythromycin, rifampin, and vancomycin (with some strain variation)Footnote 15Footnote 16.

DRUG RESISTANCE: Usually resistant to the aminoglycosidesFootnote 3, and may be resistant to tetracyclines and cephalosporins (with some strain variation)Footnote 16Footnote 17. Also resistant to nalidixic acid and sulphamethoxazole-trimethoprim (SMX-TMP)Footnote 18.

SUSCEPTIBILITY TO DISINFECTANTS: The vegetative state is susceptible to disinfectants such as 70% ethanol, 0.1% sodium hypochlorite, and 0.1N NaOHFootnote 19 . Spores may be resistant to disinfectants. Toxins are inactivated (more than 99.7%) by 20 minutes exposure to 3 mg/L free available chlorine (FAC; similar to the military disinfection procedure), and 84% inactivated by a treatment of 20 minutes at 0.4 mg/L FAC (similar to municipal water treatment procedures)Footnote 6 .

PHYSICAL INACTIVATION: Toxin is destroyed after heating for 5 minutes at greater than 85°CFootnote 1 Footnote 8 Footnote 9 . Toxins are detoxified in air within 12 hours and following exposure to sunlight within 1 to 3 hoursFootnote 9 . Spores are highly resistant to heatFootnote 2 and desiccationFootnote 2 ; therefore, it is recommended to sterilize with dry heat (2 hours at 160°C) by autoclaving (20 minutes at 121°C, 1 atm pressure) and/or by irradiationFootnote 9 .

SURVIVAL OUTSIDE HOST: Survives well in soil, water and agricultural productsFootnote 2Footnote 5.


SURVEILLANCE: Since botulism is a life threatening condition, a rapid diagnosis is essentialFootnote 9and may require testing to differentiate botulism from other neurological diseasesFootnote 6.

Food borne botulism: Can be diagnosed by demonstration of toxin in serumFootnote 1Footnote 2Footnote 5Footnote 8Footnote 15, stoolFootnote 1Footnote 2Footnote 6Footnote 8, gastric aspirateFootnote 1Footnote 2Footnote 5 or implicated foodFootnote 1Footnote 2Footnote 5, or by culture of C. botulinum from a patient's gastric aspirate or stool in a clinical caseFootnote 1Footnote 5. The mouse bioassay is the most reliable method for detection of botulinumFootnote 5Footnote 6Footnote 8.

Wound botulism: Can be diagnosed by demonstration of toxin in serum, or by positive wound cultureFootnote 1Footnote 2.

Adult infectious botulism: Can be diagnosed by demonstration of C. botulinum (or other neurotoxin producing species) and/or toxins in a patient's faeces or in autopsy specimensFootnote 1.

Intestinal (infant) botulism: Since the toxin is rarely found in the sera of infantsFootnote 1Footnote 2, faeces should be examinedFootnote 1. An ELISA has been developed for the detection of A and B toxins in children's faecal samplesFootnote 2.

Inhalational botulism: Aerosolized toxin can not usually be identified in serum or faeces, but may be detected by ELISA from nasal swabsFootnote 8.

Iatrogenic botulism: Should be suspected if patient has recently received BotoxFootnote 10Footnote 11. An immuno-PCR assay capable of detecting neurotoxin type A in the femtogram range has been developedFootnote 20.

Note: All diagnostic methods are not necessarily available in all countries.


Foodborne botulism: Within 1 hour of ingestion of suspected food, the recommended course of action is a gastric lavageFootnote 1Footnote 2, or enemasFootnote 1, and the administration of a cathartic (sorbitol)Footnote 1. In some cases intravenous administration of AB or ABEFootnote 1Footnote 2Footnote 6Footnote 8 botulinum antitoxinFootnote 1Footnote 2Footnote 5Footnote 6Footnote 8 is required, and assisted ventilation if respiratory failure occurs. Treatment may be required for weeks or monthsFootnote 5.

Wound botulism: AntitoxinFootnote 1Footnote 5, wound debridement, drainage and irrigationFootnote 1Footnote 5Footnote 13, and antibiotic treatmentFootnote 1.

Infant botulism: Requires meticulous supportive careFootnote 1. Instead of antitoxin which can cause sensitization and anaphylaxisFootnote 1Footnote 6Footnote 8, an investigational human-derived botulinal immunoglobulin (BIG) is available for the treatmentFootnote 1 and assisted respiration is given if requiredFootnote 1Footnote 5.

Intestinal botulism: Repeated administration of ABE antitoxinFootnote 6 and assisted respiration is given, if requiredFootnote 1Footnote 5.

IMMUNISATION: NoneFootnote 5.

PROPHYLAXIS: Individuals known to have eaten contaminated food should be purged with catharticsFootnote 1, given a gastric lavage and high enemasFootnote 1, and may be given equine botulinum AB or ABE antitoxinFootnote 1Footnote 6.



SOURCES/SPECIMENS: Food products, and clinical materials such as serum/blood, stool, vomit, and gastric aspiratesFootnote 5. For wound botulism: wound exudates, debrided tissue, or swab sample. Other sources include, nasal swabs from inhalational botulism patients, and environmental samples (soil, surface water)Footnote 1Footnote 2Footnote 6Footnote 9.

PRIMARY HAZARDS: Exposure to the toxin. The toxin may be absorbed after ingestion, or following contact with the non-intact skin, the eyes, or mucous membranes, including the respiratory tractFootnote 5. Inhalation of the toxin has occurred under laboratory conditionsFootnote 5Footnote 6.




CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.

PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashesFootnote 19.

OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activitiesFootnote 19.


SPILLS: Allow aerosols to settle, and, while wearing protective clothing, gently cover the spill with paper towels and apply appropriate disinfectant starting at the perimeter, working inwards towards the centre. Allow sufficient contact time before clean upFootnote 19.

DISPOSAL: Decontaminate before disposal, using steam sterilisation, incineration, or chemical disinfectionFootnote 19.

STORAGE: In locked, leak-proof containers that are appropriately labelled and securedFootnote 19.


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: September 2010.

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright ©
Public Health Agency of Canada, 2010

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