Clostridium botulinum

Food Safety Information

United States Department of Agriculture

Food Safety and Inspection Service

USDA Meat & Poultry Hotline

1-888-MPHotline

(888-674-6854)

The Food Safety and Inspection Service (FSIS) is the public health agency 

in the U.S. Department of Agriculture responsible for ensuring that the nation’s commercial supply of meat, poultry, and egg products is safe, wholesome, and correctly labeled and packaged.

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What is Clostridium 

botulinum? 

Where is Clostridium 

botulinum Found?

How is the Toxin 

Produced in Food?

What is Botulism? 

Clostridium botulinum are rod-shaped bacteria (also called C. botulinum. They 

are anaerobic, meaning they live and grow in low oxygen conditions. The bacteria form protective spores when conditions for survival are poor. The spore 

has a hard protective coating that encases the key parts of the bacterium and 

has layers of protective membranes. Within these membranes and the hard 

coating, the dormant bacterium is able to survive for years. C. botulinum is 

responsible for a disease called botulism.

Botulism is a life-threatening disease caused by the ingestion of a potent neurotoxin produced during growth of the C. botulinum bacteria. This neurotoxin 

is among the most toxic substances known; even microscopic amounts can 

cause illness or death. In the past, botulism was linked primarily to homecanned foods. In recent decades, however, botulism illnesses have been linked 

to foods such as unrefrigerated homemade salsa, baked potatoes sealed in 

aluminum foil, honey (the primary cause of botulism in infants), garlic in oil, 

and traditionally prepared salted or fermented fish.

C. botulinum is prevalent in soil and marine sediments worldwide, most commonly as spores. These spores are found everywhere. While the spores are 

generally harmless, the danger can occur once the spores begin to grow out 

into active bacteria and produce neurotoxins. A neurotoxin is a poisonous 

chemical that affects the central nervous system. It can destroy, paralyze, or 

adversely affect nerves or nerve tissue. C. botulinum produces seven different 

types of neurotoxins designated by the letters A through G; only types A, B, E, 

and F cause illness in humans.

C. botulinum spores are often found on the surfaces of fruits and vegetables 

and in seafood. The organism grows best under low-oxygen conditions and 

produces spores and toxins. The toxin is most commonly formed when food 

is improperly processed (canned) at home. C. botulinum cannot grow below 

a pH of 4.6, so acidic foods, such as most fruits, tomatoes, and pickles, can 

be safely processed in a water bath canner. However, foods with a higher pH 

(most vegetables and meats) must be processed under pressure. Therefore, a 

pressure cooker should be used. The pressure cooker will reach high-enough 

temperatures to destroy the C. botulinum spores. 

For example, if a low-acid food, such as green beans, is canned improperly 

(not canned under pressure or improperly canned using a pressure canner), 

C. botulinum bacteria and other bacteria present will be destroyed by the boiling of water and food, but the C. botulinum spores will not be destroyed. The 

canning process will remove the oxygen from the jar, creating a low-oxygen 

environment that will allow the spores to grow into active bacteria. When the 

jars are stored at room temperature, the spores can germinate and produce 

the toxin. However, the toxin is sensitive to heat and can be destroyed if the 

food in question is boiled for 10 minutes (longer at high altitudes).
Food Safety Information 2

Clostridium botulinum

How Does the Illness 

Occur?

What are the Symptoms?

What is Infant Botulism?

How Do Nitrates 

and Nitrites Prevent 

Botulism?

The Disease Botulism is a paralyzing disease affecting the body’s nervous system that is 

caused by the ingestion of one of the potent neurotoxins produced by 

C. botulinum bacterium. This neurotoxin is among the most toxic substances 

known; even microscopic amounts can cause illness. 

Symptoms of botulism usually appear within 12 to 36 hours after eating food 

containing the neurotoxin, although there have been documented cases that 

ranged from 4 hours to 8 days. The earlier the symptoms appear, the more 

serious the disease. Treatment requires quick medical attention and an antitoxin.

Once in the body, the toxin binds to nerve endings that join muscles. This 

prevents the nerves from signaling the muscles to contract. The first symptoms of botulism are nausea, vomiting, weakness, and vertigo (dizziness). 

These are followed by neurological symptoms: visual impairments (blurred or 

double vision), loss of normal throat and mouth functions (difficulty speaking and swallowing; dry mouth, throat, and tongue; and sore throat), general 

fatigue, lack of muscle coordination, and difficulty in breathing. Gastrointestinal symptoms may include abdominal pain, diarrhea, or constipation. Death 

is usually caused by respiratory failure and airway obstructions. When the 

diaphragm and chest muscles become fully involved, breathing is affected 

and results in death from asphyxia.

If botulism is caught in the early stages, the injection of an antitoxin can 

lessen the severity of the disease by neutralizing any toxin that has not yet 

bound to nerve endings. However, due to the risk of serious side effects, the 

antitoxin cannot always be used. A human-derived antitoxin is used to treat 

cases of infant botulism and is available from the California Department of 

Public Health. 

Infant botulism may affect infants under 12 months of age, but most commonly those under 2 months of age. It occurs when infants eat food, such 

as honey, that contains spores of C. botulinum that germinate, colonize, and 

produce neurotoxin in the infant’s intestinal tract. For this reason, the U.S. 

Food and Drug Administration, the Centers for Disease Control and 

Prevention, and the American Academy of Pediatrics recommend that 

honey not be given to children under 1 year of age. Also, fruits and 

vegetables should be washed before being fed to infants.

Nitrites are used in certain cured meat and poultry products to inhibit the 

growth of the bacterial spores of C. botulinum. The U.S. Department of Agriculture (USDA) authorized the use of nitrite in meat and poultry products 

beginning in 1925. 

Nitrate and nitrites are different compounds made from nitrogen and oxygen 

and are used in curing meats. (For more information on curing, see: http://

www.fsis.usda.gov/factsheets/ham/index.asp.) Both sodium nitrate and 

potassium nitrate, along with nitrites, are used to cure or preserve meats by 

slowing bacterial growth. They also prevent rancidity. 

Concern was raised in the early 1970s over the risk of nitrites reacting with 

amines in food to create a class of carcinogenic compounds called nitrosamines. Processors may use ascorbic acid (Vitamin C), erythorbic acid, or their 

salts to accelerate the combination of nitrate with the meat components so 

there will not be enough nitrite available during cooking to form nitrosamines 

and to inhibit the formation of nitrosamines during curing. Most nitrites disappear from the cured product as it combines with the meat after it has accomplished its curing effects. After cooking, as little as one-fourth may remain, 

and over time, the amount further declines.
Food Safety Questions?

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Issued January 2010

FSIS encourages the reprint and distribution of this publication for food safety 

education purposes. However, USDA symbols or logos may not be used separately to 

imply endorsement of a commercial product or service. 

Clostridium botulinum

Call the USDA Meat & Poultry Hotline

More Information

What is the Best Way to 

Prevent Botulism?

If you have a question 

about meat, poultry, or 

egg products, call the 

USDA Meat and Poultry Hotline 

toll free at 

1-888-MPHotline

(1-888-674-6854)

The hotline is open 

year-round

 Monday through Friday from 

10 a.m. to 4 p.m. ET 

(English or Spanish).

Recorded food safety 

messages are available 24 hours a day. 

Check out the 

FSIS Web site at

 www.fsis.usda.gov. 

Send E-mail questions to MPHotline.fsis@usda.gov.

The control of foodborne botulism is based almost entirely on thermal destruction (heating) of the spores or inhibiting spore germination into bacteria 

and allowing cells to grow and produce toxins in foods. To prevent foodborne 

botulism:

• Use approved heat processes for commercially and home-canned foods 

(i.e., pressure-can low-acid foods such as corn or green beans, meat, or 

poultry).

• Discard all swollen, gassy, or spoiled canned foods. Double bag the cans 

or jars with plastic bags that are tightly closed. Then place the bags in a 

trash receptacle for non-recyclable trash outside the home. Keep it out of 

the reach of humans and pets.

•	 Do not taste or eat foods from containers that are leaking, have 

bulges or are swollen, look damaged or cracked, or seem abnormal in appearance. Do not use products that spurt liquid or foam 

when the container is opened.

• Boil home-processed, low-acid canned foods for 10 minutes prior to serving. For higher altitudes, add 1 minute for each 1,000 feet of elevation.

• Refrigerate all leftovers and cooked foods within 2 hours after cooking (1 

hour if the temperature is above 90 °F).

• One of the most common causes of foodborne botulism is improperly 

home-canned food, especially low-acid foods such as vegetables and 

meats. Only a pressure cooker/canner allows water to reach 240 to 250 

°F, a temperature that can kill the spores. 

Consumers who preserve foods at home should follow the guidelines in the 

publication USDA’s Complete Guide to Home Canning, 2009 Revision, at 

http://www.uga.edu/nchfp/publications/publications_usda.html.

Information is also available from the National Center for Home Food Preservation at http://www.uga.edu/nchfp/index.html.

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