FOOD POISONING

DEFINITION

Food poisoning is a general term for health problems caused by eating contaminated food. Food may be contaminated by bacteria, viruses, toxins (poisons) from the environment, or toxins within the food itself. Symptoms of food poisoning usually include vomiting and diarrhea. Some toxins also affect the nervous system.

DESCRIPTION

Each year, millions of people suffer from bouts of vomiting and diarrhea that they blame on "something I ate." These people are usually correct. The U.S. Centers for Disease Control and Prevention (CDC) estimate that anywhere from six to thirty-three million cases of food poisoning occur in the United States each year. Many cases are mild. They pass so quickly that they are never diagnosed. On occasion, a severe outbreak affects a number of people. Newspapers, radio, and television may report on the outbreak.

Many kinds of food poisoning are caused by bacteria. The most common of these bacteria are Salmonella (pronounced SAL-mo-nel-uh), Staphylococcus aureus (pronounced STAFF-uh-lo-kock-us AW-ree-us), Escherichia coliO157:H7 (pronounced ESH-ur-ick-ee-uh KO-lie), Shigella (pronounced shih-GEL-uh), and Clostridium botulinum (pronounced klos-TRID-ee-um BOTCH-u-line-um). The pattern of disease caused by each type of bacterium is slightly different. Most of them cause inflammation of the intestines and diarrhea. Clostridium botulinum is an exception.

Food and water can also be contaminated by other agents, such as viruses, heavy metals (such as lead, cadmium, and mercury), and poisons produced within the food itself. Mushroom and shellfish poisoning, for example, are caused by poisons produced within the food itself.

Careless food handling creates conditions for the growth of bacteria that make people sick. Food can be contaminated at many different points during its trip from farm to table. Vegetables that are eaten raw, such as lettuce, may be contaminated by bacteria in the soil in which they were grown. They can also be contaminated during washing and packing. Home canning can also lead to food poisoning. Foods may be cooked at too low a temperature or for too short a time. Bacteria may not be killed.

Raw meats carry many bacteria that can cause food poisoning. The U.S. Food and Drug Administration (FDA) estimates that at least 60 percent of all raw poultry sold to consumers carries some disease-causing bacteria. Other raw meat products and eggs are also contaminated, but to a lesser degree. Thorough cooking kills these bacteria and makes the food harmless. However, properly cooked food can become recontaminated. It may come into contact with plates, cutting boards, counter tops, and utensils that have not been properly cleaned.

Cooked foods can also become contaminated in other ways. There are disease-causing bacteria everywhere in the environment. For example, experts estimate that half of all healthy people have the Staphylococcus aureus bacterium in their nasal (nose) passages and throat and on their skin and hair. These bacteria are easily transferred to food. A food handler may rub a runny nose and then touch freshly cooked food. Bacteria grow well at room temperature. They will rapidly reproduce to a level where they can make people sick. To prevent this growth, food must be kept hot or cold, but never just warm.

The food supply in the United States is probably the safest in the world. Still, anyone can get food poisoning. Serious outbreaks are rare. When they do occur, they strike some groups of people harder than others. The very young, the very old, and those with weakened immune systems are especially at risk. For example, people in these categories are twenty times more likely to become infected with the Salmonella bacterium than the general population.

People who travel outside the United States also have a greater chance of getting food poisoning. In many countries, less attention is paid to sanitation, water purification, and good food handling procedures. People living in institutions such as nursing homes are also more likely to get food poisoning.

CAUSES

Food poisoning is caused by toxins released by bacteria and other organisms. These toxins (except those from Clostridium botulinum) cause inflammation

A magnified image of Escherichia Coli (E. coli). (© 1997. Reproduced by permission of

Custom Medical Stock Photo

.)

of the stomach and intestines. The result is abdominal (stomach) muscle cramping, vomiting, diarrhea, fever, and possibly dehydration. Dehydration is the process by which the body loses water faster than it should.

Salmonella

About fifty thousand cases of Salmonella poisoning were reported in the United States in 1995. The CDC estimates that between two and four million cases probably went unreported. Many people who have Salmonella poisoning are not aware that they have it. They do not see a doctor for treatment.

The main sources of Salmonella poisoning are egg yolks from infected chickens, raw and undercooked poultry and other meats, dairy products, fish, and shrimp. The bacterium is also found in many other foods. Egg yolks may be the most serious problem. The CDC estimates that 1 out of every 50 Americans consumes contaminated egg yolk in a year. Salmonella poisoning can be avoided by thoroughly cooking any of the foods in which it occurs. The bacteria are also found in the feces of pet reptiles, such as turtles, lizards, and snakes.

About 1 out of every 1,000 people get food poisoning from Salmonella. Of these people, two-thirds are under the age of twenty. The majority are under the age of nine. Most cases occur during the warm months between July and October.

Staphylococcus aureus

Staphylococcus aureus occurs everywhere in the environment. It is found in dust, air, and sewage. The usual method of transmission is by food handlers who use poor sanitary practices. For example, a cook may forget to wash his or her hands after using the bathroom. Bacteria can then be transferred from the cook's hands to food. Almost any kind of food can be contaminated in this way, but some foods are especially likely to be contaminated. These foods include salad dressings, milk products, cream pastries, and any food kept at room temperature.

It is difficult to estimate the number of Staphylococcus aureus poisoning cases that occur. Most cases are quite mild, and the patient never sees a doctor.

Escherichia coli (E. coli)

E. coli is a very common bacterium. It occurs in many different strains (forms). Some forms are beneficial. They may even be essential to the normal function of our digestive systems. The strain that causes most cases of food poisoning is E. coli O157:H7. Food poisoning caused by this bacterium occurs in about 3 out of every 10,000 people. The primary sources of E. coli are foods obtained from cows, such as dairy products and beef, especially ground beef.

Campylobacter jejuni (C. jejuni)

According to the FDA, Campylobacter jejuni (pronounced KAMP-puh-lo-BAK-tur jeh-JOO-ni) is the leading cause of bacterial diarrhea in the United States. Anyone can get food poisoning from C. jejuni. However, children under the age of five and young adults between the ages of fifteen and twenty-nine are most frequently affected.

C. jejuni occurs in healthy cattle, chickens, birds, and flies. It is also found in ponds and stream water. The bacterium is very potent (powerful). Consuming no more than a few hundred C. jejuni bacteria can cause a person to become ill.

Shigella

Shigella is a common cause of diarrhea in people who travel to developing countries. In these countries, sanitation practices may not be as well developed as they are in the United States. The Shigella bacterium grows well in contaminated food and water, in crowded living conditions, and in areas with poor sanitation. Shigella toxins infect the small intestine.

Clostridium botulinum (C. botulinum)

C. botulinum causes a disease known as botulism (pronounced BOTCH-u-liz-um). Two forms of botulism are known—adult and infant botulism. The C. botulinum bacterium is unlike any other bacterium in that it causes food poisoning in three ways.

First, C. botulinum is an anaerobic (pronounced AN-uh-RO-bik) bacterium. The term anaerobic means "able to live only in the absence of oxygen." That is, C. botulinum bacteria exposed to the air die quickly. Second, the toxins released by C. botulinum are neurotoxins. Neurotoxins are poisons that attack the nervous system, such as the brain and spinal cord. They may cause paralysis without producing any of the more traditional symptoms of food poisoning, such as vomiting and diarrhea. Third, botulism is a much more serious disease than other forms of food poisoning. People can die after consuming only very small amounts of the bacterium.

Adult botulism is usually caused by contaminated foods that are canned improperly at home. Less commonly, the C. botulinum bacterium is found in commercially canned foods. When foods are canned (at home or in a factory), they must first be heated to a high temperature. The temperature must be high enough to kill all C. botulinum bacteria that may be present. If the temperature is too low, some bacteria may survive. In such cases, conditions inside the can are an ideal setting for the bacteria to begin growing. No oxygen is present, and the canned food provides all the nourishment the bacteria need.

SYMPTOMS

How serious the symptoms of food poisoning are depends on many factors. These factors include the kind of bacteria, the amount consumed, and the individual's general health and sensitivity to the bacterial toxin.

(Source: Food Safety and Inspection Service, U.S. Department of Agriculture. Reproduced by permission of

Stanley Publishing

.)

COMMON PATHOGENS CAUSING FOOD POISONING
Pathogen	Common Host(s)
(Source: Food Safety and Inspection Service, U.S. Department of Agriculture. Reproduced by permission of Stanley Publishing.)
Campylobacter	Poultry
E.coli 0157:H7	Undercooked, contaminated ground beef
Listeria	Found in a variety of raw foods, such as uncooked meats and vegetables, and in processed foods that become contaminated after processing
Salmonella	Poultry, eggs, meat, and milk
Shigella	This bacteria is transmitted through direct contact with an infected person or from food or water that become contaminated by an infected person
Vibrio	Contaminated seafood

Salmonella

Symptoms of Salmonella poisoning appear twelve to seventy-two hours after a person has eaten contaminated food. These symptoms are the traditional food poisoning symptoms, such as abdominal pain, diarrhea, vomiting, and fever. The symptoms usually last two to five days. In the most severe cases, dehydration can be a serious problem. People usually recover without being treated with antibiotics. However, they usually continue to feel tired for a week after the symptoms have passed.

Staphylococcus aureus

Symptoms of Staphylococcus aureus poisoning usually appear quickly, often within eight hours of eating the contaminated food. The most serious symptoms are vomiting, diarrhea, and severe abdominal cramps. These symptoms usually last three to six hours, and rarely more than twenty-four hours. Most people recover without medical assistance. Deaths are rare.

Escherichia coli (E. coli)

Symptoms of E. coli poisoning appear more slowly than symptoms of other kinds of food poisoning. These symptoms normally first arise one to three days after eating contaminated food. One symptom is severe abdominal cramps. Another symptom is diarrhea that is watery at first, but then becomes bloody. Both fever and vomiting are likely to be absent with E. coli poisoning. In most cases, the watery, bloody diarrhea disappears after one to eight days.

A possible complication of E. coli infection, especially in children under five and elderly people, is hemolytic uremic syndrome (HUS). This disease causes the kidneys to fail and red blood cells to be destroyed. Most people recover fully from HUS, but the disease can be fatal.

Campylobacter jejuni (C. jejuni)

The first symptoms of C. jejuni poisoning appear two to five days after eating contaminated food. These symptoms include fever, abdominal pain, nausea, headache, muscle pain, and diarrhea. The diarrhea can be watery or sticky. It may also contain blood. Symptoms of the infection last from seven to ten days. Relapses (reoccurrences of the infection) occur in about onequarter of all patients. Dehydration can be a serious complication.

Shigella

Symptoms of Shigella poisoning appear thirty-six to seventy-two hours after eating contaminated food. These symptoms are slightly different from other forms of food poisoning. The usual watery diarrhea, nausea, vomiting, abdominal cramps, and fever are present. But up to 40 percent of children infected with the bacterium show neurological (nervous system) problems. These symptoms include seizures, confusion, headache, lethargy (listlessness), and a stiff neck.

The disease usually lasts two to three days. Dehydration is a common complication. Most people recover on their own. But they may feel exhausted for days or weeks after symptoms have disappeared. Children who are malnourished (poorly fed) or who have weakened immune systems can die of the infection.

Clostridium botulinum (C. botulinum)

Symptoms of adult botulism usually appear eighteen to thirty-six hours after the contaminated food is eaten. The first signs of botulism are a feeling of weakness and dizziness, followed by double vision. As the bacteria spread through the nervous system, paralysis begins. The patient finds it difficult to speak and swallow. Eventually, the muscles of the respiratory (breathing) system are affected. The patient may die of asphyxiation (suffocation; pronounced as-FIK-see-A-shun). People who show the symptoms of botulism require immediate medical attention.

Infant botulism was first recognized in 1976. It differs from adult botulism in both causes and symptoms. Infant botulism occurs when a child under the age of one year inhales or swallows the spores of C. botulinum. Spores are reproductive cells from non-flowering plants, such as mosses and ferns. C. botulinum spores are found in the soil. A more common source in the case of food poisoning, however, is honey.

Once inside an infant's body, C. botulinum spores become stuck in the baby's intestines. They begin to grow and release their neurotoxin. Symptoms begin to appear very gradually. Initially, the baby is constipated. Eventually, it loses interest in eating, begins to drool, becomes weak and lethargic, and makes a very distinctive crying sound. Eventually the baby loses its ability to control its head muscles. Beyond that point, paralysis sets in throughout the baby's body.

DIAGNOSIS

An important step in diagnosing food poisoning is studying the behavior of groups of people. Doctors try to find out if a number of people have eaten the same food and have the same symptoms. If that is the case, the food may have been contaminated. Diagnosis of food poisoning can be confirmed with a stool culture. A sample of feces is taken from the patient. The sample can then be studied to see whether the bacteria that cause food poisoning are present. Laboratory tests can also be conducted on the contaminated food. The bacteria present can be detected.

The diagnosis of botulism presents different problems. First, the characteristics of botulism are very different from those of other forms of food poisoning. Second, a rapid diagnosis is essential. A person who has botulism can become ill and die very quickly.

Many cases of food poisoning are never diagnosed. People may not even realize that they are sick. In most cases, the symptoms of food poisoning disappear quickly.

TREATMENT

People with food poisoning should modify their diet during the period of illness. They should drink clear liquids frequently, but in small amounts. As their condition improves, soft, bland foods can be added to the diet. A commonly recommended diet is called the BRAT diet. The BRAT diet gets its name from the four foods it includes: banana, rice, applesauce, and toast. Milk products, spicy food, alcohol, and fresh fruit should be avoided until all symptoms disappear. These dietary changes are often the only treatment necessary for food poisoning.

In all cases of food poisoning except botulism, the major concern is dehydration. Diarrhea and vomiting both result in the loss of water and electrolytes from the body. Electrolytes are chemicals that control many important body functions. When they are lost, normal body functions may be disrupted. This problem can be especially serious in young children and elderly people.

Simple dehydration is easily treated. Over-the-counter (non-prescription) fluids that restore electrolytes can be purchased in any drug store. These fluids are usually pleasant tasting and restore lost water and electrolytes efficiently. If dehydration is serious, further treatment may be necessary. Fluids may have to be injected directly into a person's bloodstream.

In very serious cases of food poisoning, medications may be given to stop cramping and vomiting. Nothing should be done to stop diarrhea, however. Diarrhea helps remove toxins from the body.

In some cases, doctors may decide to use drugs to treat food poisoning. The most frequently prescribed antibiotics are a combination of trimethoprim and sulfamethoxazole (pronounced tri-METH-o-prim and SULL-fuhmeth-OCK-suh-zole, trade names Septra, Bactrim), ampicillin (pronounced AMP-ih-SIL-in, trade names Amcill, Polycill), or ciprofloxacin (pronounced SIP-ro-FLOK-suh-sin, trade names Ciloxan, Cipro).

The treatment of botulism is a much more difficult problem. A botulism antitoxin exists. The antitoxin counteracts the poison produced by C. botulinum. But it must be given within seventy-two hours after symptoms first appear. After that time, the antitoxin has no effect. The antitoxin also cannot be used on infants.

Both infants and adults who have botulism require hospital care. Patients may need to have a mechanical device to help them breathe until paralysis disappears.

Alternative Treatment

Alternative practitioners offer the same advice regarding diet modification as that described above. They also recommend taking charcoal tablets. Charcoal has the ability to attract and soak up toxins in the body. Other recommended treatments include two bacteria found in milk products, Lactobacillus acidophilus (pronounced LACK-toe-buh-sill-us a-suh-DAH-fuh-luss) and Lactobacillus bulgaricus (pronounced LACK-toe-buh-sill-us bul-GAR-ihkuss), and citrus seed extract.

A fluid to replace water and electrolytes can be made at home. It is made by adding one teaspoon of salt and four teaspoons of sugar to one quart of water. Two herbs that are recommended for treating forms of food poisoning other than botulism are Arsenicum album and Nux vomica.

PROGNOSIS

Except for botulism, most cases of food poisoning clear up on their own within a week without medical assistance. The patient may continue to feel tired for a few days after the symptoms disappear. As long as a person does not become dehydrated, there are usually no long-term symptoms. Deaths are rare. They tend to occur in the very young, the very old, and people with weakened immune systems.

Long-term effects are somewhat more common with Salmonella. Arthritis-like symptoms may occur three to four weeks after the original infection. Death from Salmonella is rare, but not unheard of. Most of these deaths have occurred among elderly people living in nursing homes.

Food poisoning caused by E. coli can also be serious, but usually in children rather than adults. The bacterium can attack platelets and red blood cells. Platelets are needed to make blood clot. In about 5 percent of the people infected with E. coli, this problem is so serious that their kidneys begin to fail. Kidney dialysis may be necessary. Kidney dialysis is a procedure in which a machine does the kidney's job of filtering out the body's waste products.

Botulism is the deadliest form of food poisoning. With prompt medical care, prognosis is good. Less than 10 percent of patients die. Without medical care, however, prognosis is very poor. The rate of death is very high.

PREVENTION

Food poisoning is almost entirely preventable. Good sanitation and food handling techniques are the key to avoiding the disease. The instructions to keep in mind are as follows:

• Keep hot foods hot and cold foods cold.
• Cook meat to the recommended internal temperature. Use a meat thermometer to be sure. Cook eggs until they are no longer runny.
• Refrigerate leftovers promptly. Do not let food stand at room temperature.
• Avoid contaminating surfaces and foods with the juices of uncooked meats.
• Wash fruits and vegetables before using.
• Purchase pasteurized dairy products and fruit juices. Pasteurized foods are heated to a temperature hot enough to kill the bacteria that cause food poisoning.
• Throw away bulging or leaking cans or any food that smells spoiled.
• Wash hands well before and during food preparation and after using the bathroom.
• Sanitize food preparation surfaces regularly.

Proper handling of food can help prevent food poisoning. This fast-food worker uses tongs to turn hamburger patties. (Reproduced by permission of

AP/Wide World Photo

)

FOR MORE INFORMATION

Books

Cody, Mildred McInnes. Safe Food for You and Your Family. Minneapolis: Chronimed Publishers, 1996.

Latta, Sara L. Food Poisoning and Foodborne Diseases. Hillside, NJ: Enslow Publishers, Inc., 1999.

Patten, Barbara J. Food Safety. Vero Beach, FL: The Rourke Book Company, Inc., 1997.

Scott, Elizabeth, and Paul Sockett. How to Prevent Food Poisoning : A Practical Guide to Safe Cooking, Eating, and Food Handling. New York: John Wiley & Sons, 1998.

Periodicals

U.S. Food and Drug Administration. "The Unwelcome Dinner Guest: Preventing Food-Borne Illness." FDA Consumer (December 1997).

Web sites

"Botulism (Clostridium botulinum)." [Online] http://www.cdc.gov/ncidod/diseases/foodborn/botu.htm (accessed on October 19, 1999).

Centers for Disease Control and Prevention. [Online] http://www.cdc.gov (accessed on October 19, 1999).

U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. Bad Bug Book. [Online] http://www.cfsan.fda.gov (accessed on October 19, 1999).