Botulism

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Botulism

Botulism is an extremely serious disease caused by the bacterium Clostridium botulinum. C. botulinum release one of the most potent toxins known—one gram of botulinum toxin theoretically can kill one million people. The toxin is swift-acting. It kills by binding to nerve cells, thereby causing paralysis of the muscles used in breathing.

First coined in the 1870s, the term botulism comes from the Latin word for sausage, botulus, since botulism used to be associated with eating sausage. Although botulism is still commonly associated with food contamination in the United States, it is more likely to occur from eating plants, not meat.

The canning connection

Plant foods associated with botulism are canned vegetables . In a typical scenario, vegetables contaminated with C. botulinum from the soil are not washed adequately and subjected to temperatures inadequate for killing the bacteria . As the vegetable sits on the shelf, botulinum toxin is released into the can. Because the toxin is odorless and colorless, the unsuspecting person eats the contaminated vegetable. Vegetables having neutral pH are most likely to harbor botulinum bacteria. Examples are beans, peas, and corn. Canned vegetables with low pH, such as canned tomatoes, are resistant to the growth of C. botulinum because of the acidic environment.

Fortunately, this scenario is rare as modern commercial canning techniques have virtually eliminated the risk of botulism. However, many home canners do not know the proper prevention techniques. About 10 outbreaks of botulism still occur each year in the United States. Most of these outbreaks are traced to food poisoning . Less frequently, botulism in humans stems from wound infections, or even more rarely a gastrointestinal infection of newborns. In animals, botulism can be traced to the eating of contaminated animal carcasses, or hay or grass that has been contaminated by a dead, toxic animal. Animals that characteristically feed on dead animals, such as vultures , are apparently resistant to the effects of botulinum toxin.

Clostridium botulinum

Clostridium botulinum has been classified into eight different strains. Each strain releases the deadly toxin but in slightly different forms. Humans are susceptible to four of these eight toxins; the other four are deadly in cattle, sheep , and horses . C. botulinum is a strict anaerobe, meaning it survives only in conditions completely lacking oxygen . In fact, the presence of oxygen kills C. botulinum. However, the bacteria can survive for long periods of time by producing endospores. Endospores are small, protective capsules that surround the bacteria. They can withstand incredible extremes of temperature . The C. botulinum endospore can survive several hours at 212°F (100°C, the boiling point of water ) and 10 minutes at 248°F (120°C). C. botulinum endospores also can survive at -374°F (-226°C). The endospores can even resist radiation . The botulism endospore is one of the most hardy organisms on Earth .

The botulinum toxin is in fact a group of seven closely related poisons produced by the bacteria. The fatal toxin the bacteria produces is a neurotoxin—it binds to nerve cells. Once bound, the toxin prevents the release of a neurotransmitter called acetylcholine from the nerve cells. Since nerve cells use the release of acetylcholine to transmit nerve impulses, preventing the release of acetylcholine stops the transmission of nerve impulses. Muscle paralysis eventually results.

The toxin targets nerve cells of the peripheral nervous system which govern the muscles associated with breathing. The muscles that control the tongue, pharynx, and ribs succumb swiftly to the toxin, becoming paralyzed within hours of ingestion of contaminated food. If rapid diagnosis is not made and treatment with an antitoxin (a substance that blocks the binding of the toxin to nerve cells) is not started, death can result quickly.

Symptoms

Symptoms can occur anywhere from 12 to 36 hours to eight days after eating toxin-contaminated food. The early symptoms of botulism are mild. Dizziness, fatigue, and weakness are common complaints. None of the early symptoms indicate the seriousness of the disease. Later, neurological symptoms develop, including difficulty in speaking and swallowing, and double vision . Fever rarely is present. Abdominal distension can further complicate the diagnosis leading to the incorrect conclusion of appendicitis. As more toxin binds to more nerve cells, paralysis sets in. Weakness of the muscle groups in the neck, extremities, and respiratory muscles is followed by complete paralysis.

Treatment

Because botulism is caused by a toxin and not the effects of the bacteria, antibiotics are not usually prescribed. The treatment for botulism is the antitoxin that neutralizes the toxin in the body. The antitoxin must be given early in the course of the disease to be effective. The antitoxin is useless if given too late, for too many nerve cells already are affected by the toxin. A botulism patient also must receive intensive, supportive care, such as a respirator , to assist breathing. Sometimes dialysis , a process that artificially cleanses the blood , is used to assist the kidneys in removing the toxin from the bloodstream.

Prevention

The risk of botulism has been virtually eliminated from the commercial canning industry, which uses sterilization techniques to kill the C. botulinum spores. For the home canner it is essential to follow recommended guidelines to prevent the growth of C. botulinum. These guidelines are:

All non-acidic foods, such as green beans and corn, must be canned using a pressure cooker. Acidic foods, such as tomatoes and citrus fruits , contain natural acids that kill the botulism bacteria.
To can non-acidic foods, cook them at 10 pounds of pressure at a temperature of 248°F (120°C) for 80 minutes.

Obviously, canning non-acidic foods requires special equipment. If you are not sure about the origin or safety of any home-canned food do not eat it. Dispose of the can safely and be sure to wash hands and touched surfaces thoroughly with bleach or ammonia .

The toxin can also be inactivated if the canned vegetable is cooked at 176°F (80°C) for five minutes or boiled for one minute before eating.

It is also wise to be wary of uncooked fish and meats. Sushi, a popular Japanese dish of raw fish, and venison have been known to spread botulism. All meats should be cooked thoroughly to kill the botulism endospores.

Because of its potent effects upon the human nervous system, botulinum toxin has been investigated for use in the treatment of various neurological diseases. The purified toxin used as a drug, called Botox, is used to treat conditions in which the nervous system cannot adequately control muscles, resulting in debilitating spasms. By its nature, the toxin induces muscular paralysis and is therefore useful in alleviating spasms in disorders such as cerebral palsy, spasmotic dysphonia (vocal spasms), facial spasms, and strabismis (squinting spasms of the eyelids). More controversially, Botox is also used by plastic surgeons in the temporary elimination of facial wrinkles. Administered as an injection, the toxin creates a temporary loss of muscle tone in areas of wrinkling. The result is wrinkle removal. Having reportedly few risks and complications, cosmetic Botox treatment is temporary. Injections initially last only three to four months, eventually requiring one to two injections per year for sustained effects on wrinkles. Botox is most used to eliminate the vertical wrinkles of the forehead in between the eyebrows (called glabellar frownlines) and so-called "crow's feet," wrinkles at the corners of eyes. The value of the cosmetic use of such a potent biological toxin should be weighed carefully against any potentially harmful effects of treatment.

Resources

books

Francis, Frederick. Wiley Encyclopedia of Food Science andTechnology. New York: Wiley, 1999.

Houschild, Andreas H.W., and Karen L. Dodds, eds. Clostridium botulinum: Ecology and Control in Foods. New York: M. Dekker, 1993.

Lance, Simpson L., ed. Botulinum Neurotoxin and TetanusToxin. San Diego: Academic Press, 1989.

periodicals

Binder, W.J. "Botulinum Toxin Type A (Botox) For Treatment Of Migraine Headache." Otolaryngology And Head And Neck Surgery 123, no. 6 (2000): 669–676.

Jankovic, Joseph, and Mitchell F. Brin. "The Therapeutic Uses of Botulinum Toxin." New England Journal of Medicine 324 (April 25, 1991): 1186.

Morse, Dale L., et. al. "Garlic-in-Oil Associated Botulism: Episode Leads to Product Modification." American Journal of Public Health 80 (November 1990): 1372.

Nebel, Diane. "Case Study: Botulism in Home-Canned Food." Journal of Environmental Health 54 (July-August 1991): 9.

"Preventing Food Poisoning." Professional Nurse 18, no. 4 (2002): 185-186.

Kathleen Scogna