Food poisoning

Definition

Food poisoning refers to illness arising from eating contaminated food. Food may be contaminated by bacteria, viruses, environmental toxins, or toxins present within the food itself, such as the poisons in some mushrooms or seafood. Symptoms of food poisoning are usually gastrointestinal, such as nausea , abdominal pain , vomiting , and/or diarrhea . Some food-borne toxins can affect the nervous system. Food poisoning is sometimes called bacterial gastroenteritis or infectious diarrhea and is sometimes incorrectly called ptomaine poisoning.

Description

Every year millions of people of all ages suffer from bouts of vomiting and diarrhea blamed correctly on something they ate. According to the Centers for Disease Control and Prevention (CDC), up to 33 million cases of food poisoning are reported in the United States each year. Many cases are mild and pass so rapidly that they are never diagnosed. Occasionally a severe outbreak affects many people at once, creating a newsworthy public health hazard. Although the food supply in the United States is probably one of the safest in the world, anyone can get food poisoning. Outbreaks have occurred in schools and colleges (up to 25 incidents reported annually in the United States), among restaurant clientele, in institutions such as long-term care facilities, and in other settings serving the public. Serious outbreaks are rare. When they occur, the very young, the very old, and those with weakened immune systems are subject to the most severe and life-threatening cases.

A variety of bacteria cause food poisoning, including Salmonella, Staphylococcus aureus, Campylobacter jejuni, Escherichia coli, Shigella, and Clostridium botulinum. Each type of bacteria has a different incubation period and duration, and all except the botulinum toxin cause inflammation of the intestines and diarrhea. Food and water can also be contaminated by viruses such as the Norwalk and hepatitis viruses. Environmental toxins (heavy metals) in foods or water, and poisonous substances in certain foods such mushrooms and shellfish are other causes of food poisoning.

Careless food handling between farm and table may create conditions for the growth of bacteria. Vegetables eaten raw, such as lettuce, may be contaminated by bacteria in soil, water, and dust during washing and packing. Home canned and commercially canned food may be improperly processed at too low a temperature or for too short a time to kill bacteria.

Raw meats carry many bacterial contaminants. The United States Food and Drug Administration (FDA) estimates that 60 percent or more of raw poultry sold at retail carries some disease-causing bacteria. Other raw meat products and eggs are contaminated to a lesser degree. Although thorough cooking kills bacteria and makes the food harmless, recontamination can occur in properly cooked food if it comes into contact with cutting boards, countertops, or utensils that were used with raw meat and not cleaned and sanitized after use. Food can also become contaminated by environmental contaminants and by food handlers carrying bacteria on their hands while preparing foods for the public.

It is estimated that 50 percent of healthy people have staphylococcus organisms in their nasal passages and throats and on their skin and hair. Rubbing a runny nose and then touching food can introduce the bacteria into cooked food. Bacteria flourish at room temperature and grow rapidly in quantities capable of causing illness. To prevent this growth, food must be kept hot or cold but never just warm or at room temperature.

Travel to countries where less attention is paid to sanitation, water purification, and good food-handling practices may expose individuals to bacterial contaminants. Institutional food preparation also increases the risk of food poisoning, especially if food is allowed to stand on warming trays, under warming lights, or at room temperature before being served.

Transmission

Food poisoning is not spread from one individual to another but through direct contact with the causative bacteria, viruses, or other toxins in consumed food.

Demographics

The Centers for Disease Control and Prevention (CDC) estimates that there are from six to 33 million cases of food poisoning in the United States annually, affecting men, women, and children. Food poisoning by E. coli occurs in three out of every 10,000 people. One out of every 1,000 people are reported to have food poisoning caused by Salmonella ; two-thirds are young people under age 20, and the majority are children under age nine. Although camplyobacter infections can occur in anyone, children under age five and young adults between ages 15 and 29 are more frequently infected.

Causes and symptoms

Classic food poisoning cases are caused by a variety of bacteria. The most common are the following:

• Salmonella
• Staphylococcus aureus
• Campylobacter jejuni
• Escherichia coli
• Shigella
• Clostridium botulinum

Food poisoning symptoms occur when food-borne bacteria release toxins or poisons as a byproduct of their growth in the body. These toxins (except those from C. botulinum ) cause inflammation of the stomach lining and the small and/or large intestines, resulting in abdominal muscle cramps , vomiting, diarrhea, and fever . The severity of symptoms depends on the type of bacteria, the amount consumed, and the individual's general health and sensitivity to the toxin. Dehydration can result from loss of fluids through persistent vomiting and diarrhea; it is one of the most frequent and serious complications of food poisoning. When more fluids are being lost than are replaced, dehydration may occur in the very young and in the elderly, as well as in individuals who take diuretics.

Salmonella

A 2001 CDC report states that culture-confirmed cases of salmonella poisoning affected almost 50,000 people in the United States. However, it is believed that between 2 and 4 million unconfirmed cases actually occur each year. Salmonella is found in egg yolks from infected chickens, raw and undercooked poultry and other meats, dairy products, fish, shrimp, and many other foods. The CDC estimates that one of every 50 consumers is exposed to a contaminated egg yolk each year, although thorough cooking kills the bacteria, making the food harmless. Salmonella is also found in feces of pet reptiles such as turtles, lizards, and snakes. Most cases of salmonella poisoning occur in the warm months between July and October.

Symptoms of food poisoning, such as abdominal pain, diarrhea, vomiting, and fever, begin eight to 72 hours after eating food contaminated with salmonella. Symptoms generally last one to five days. Dehydration can be a complication of severe cases with persistent vomiting and/or diarrhea. People generally recover without antibiotic treatment, although they may feel tired for a week or so after the active symptoms subside.

Staphylococcus aureus

Staph organisms are found on humans and in the environment in dust, air, and sewage. The bacteria are spread primarily by food handlers using poor sanitary practices. Almost any food can be contaminated, but salad dressings, milk products, cream pastries, and any food kept at room temperature, rather than hot or cold, are likely candidates. It is difficult to estimate the number of annual cases of Staphylococcus food poisoning because its symptoms are so similar to those caused by other food-borne bacteria. Many cases are mild. Victims may miss a day of school or work but never see a doctor for confirmation of food poisoning. Symptoms appear rapidly, usually one to six hours after the contaminated food is eaten. Acute symptoms of vomiting and severe abdominal cramps without fever usually last three to six hours and rarely more than 24 hours. Most people recover without medical assistance. Deaths are rare.

Escherichia coli (E. coli)

The many strains of E. coli are not all harmful. Nonpathogenic E. coli are, in fact, a major part of normal gut flora. The strain that causes the most severe food poisoning, however, is E. coli O157:H7, which affects three people in every 10,000. The food-borne organisms are found and transmitted mainly in food derived from cows, such as raw milk and raw or rare ground beef. Fruit or vegetables can also be contaminated.

Symptoms of E. coli poisoning are slower to appear than those caused by other food-borne bacteria. Because E. coli toxins are produced in the large intestine rather than higher up in the digestive system, symptoms typically occur from one to three days after eating contaminated food. Those affected have severe abdominal cramps and watery diarrhea that usually becomes bloody within 24 hours, a condition that can last from one to eight days. There is little or no fever and vomiting occurs only rarely.

Campylobacter jejuni

Campylobacter is the leading cause of bacterial diarrhea worldwide, responsible for more cases (2 million or more) of bacterial diarrhea in the United States than Shigella and Salmonella combined. Campylobacter is carried by healthy cattle, chickens, birds, and flies. It is also found in ponds and stream water and has been found in bottled water and on salad vegetables washed with water. Although eating chicken is a known risk factor, drinking water and eating salads have not been considered significant risks until studies of causes released in 2003 showed possible association with Campylobacter diarrheal infections. It is not known whether contamination occurs at the site of production or in the home or institution after contact with other contaminated foods, surfaces, or utensils. The ingestion of only a few hundred Campylobacter bacteria can cause food poisoning symptoms, which may begin two to five days after eating contaminated food. Symptoms will typically include fever, abdominal pain, nausea, headache , muscle pain, and diarrhea. The diarrhea can be watery or sticky and may contain blood. Symptoms last from seven to ten days and relapses occur in about one-fourth of infected individuals. Dehydration is a common complication. Other complications, such as arthritis-like joint pain and hemolytic-uremic syndrome (HUS), occur in rare cases.

Shigella

Shigella is a common cause of diarrhea in travelers to developing countries. It is associated with contaminated food and water, crowded living conditions, and poor sanitation. The bacterial toxins affect the small intestine. Symptoms of Shigella infection appear about 36–72 hours after eating contaminated food. In addition to the familiar watery diarrhea, nausea, vomiting, and abdominal cramps, the individual may also have chills, fever, and neurological symptoms. The diarrhea may be quite severe with cramping and progresses to classic dysentery. Up to 40 percent of children with severe infections show neurological symptoms. These include confusion, headache, lethargy, a stiff neck, and possible seizures. The symptoms of food poisoning by Shigella organisms may resemble meningitis and a differential diagnosis must be made by isolating the causative bacteria.

The disease runs its course usually in two to three days but may last longer. Dehydration is a common complication. Most people recover on their own, although they may feel exhausted. Children who are malnourished or have weakened immune systems may be severely affected and death can result.

Clostridium botulinum

C. botulinum causes both adult and infant botulism and differs significantly from other contaminants in its sources and symptoms. C. botulinum 's common food-borne form is an anaerobic bacterium that can only live and reproduce in the absence of oxygen. Exposure to the botulinum toxin usually occurs while eating contaminated food stored in an airless environment, as in home-canned or commercially canned or vacuum-packed food. Also, botulinum toxin is a neurotoxin that blocks the ability of motor nerves to release acetylcholine, the neurotransmitter that relays nerve signals to muscles. This neurological process can result in unresponsive muscles, a condition known as flaccid paralysis. Breathing may be severely compromised in progressive botulism because of failure of the muscles that control the airway and breathing. In infants, botulism may be caused by specific types of clostridia obtained from soil, inhaled spores, or honey containing the spores. Contamination from any of the sources results in growth of the bacteria in the infant's intestine and production of the neurotoxin.

Infant botulism is a form of botulism first recognized in 1976 that differs from food-borne botulism. Infant botulism occurs when a child younger than one year ingests the spores of C. botulinum. Although these spores are commonly found in soil, honey is a more frequent source of spores causing infant botulism by lodging in the baby's intestinal tract and producing the neurotoxin. Onset of symptoms is gradual. Initially, the baby is constipated, followed by poor feeding, lethargy, weakness, drooling, and a distinctive wailing cry. Eventually, the baby loses the ability to control its head muscles. From there the paralysis progresses to the rest of the body. Immediate treatment is required to avoid neurological complications and death. Infant botulism is much more likely to be fatal than other food poisoning infections. Infant botulism is a special form of food poisoning not related to the food-borne toxins that cause adult botulism.

Adult botulism outbreaks are usually associated with toxins found in home-canned food, although poisoning occasionally results from eating commercially canned or vacuum-packed foods. C. botulinum grows well in non-acidic, oxygen-free environments, meaning that if the cooking temperatures are too low or the cooking time too brief the bacteria in the food are not killed. Instead, bacteria may reproduce inside the can or jar, releasing the deadly neurotoxin. Heating canned food to boiling for ten minutes can render the toxin harmless. However, consuming even a very small amount of the toxin can result in serious illness or death because of lethal neurological complications.

Symptoms of adult botulism appear about 18–36 hours after the contaminated food is eaten, although times of onset have been documented ranging from four hours to eight days. Initially a person suffering from botulism feels weak and dizzy and later experiences double vision. Symptoms progress to difficulty speaking and swallowing. Paralysis moves down the body, and when the respiratory muscles are paralyzed, death can result from asphyxiation. Individuals with any signs of botulism poisoning must receive immediate emergency medical care to increase their chance of survival.

When to call the doctor

Any unexplained abdominal pain accompanied by persistent vomiting or diarrhea, whether or not a food source is suspected, should be reported to the doctor. A child having difficulty swallowing, speaking, holding the head up, or maintaining an upright posture should receive emergency medical attention. Signs of confusion, lethargy, headache, stiff neck, or seizures also require immediate medical attention.

Diagnosis

One important part of diagnosing food poisoning is the need for doctors and community health professionals to determine if a number of people have eaten the same food and show the same symptoms. If this can be proven, food poisoning is strongly suspected. The diagnosis is confirmed when the suspected bacteria is identified in the culture of a stool sample or a fecal smear from the affected individual. In some cases, the suspected bacteria, virus, or toxin can be identified in the actual food source.

Laboratory tests are used to make a definitive diagnosis, but treatment of symptoms may be started immediately without waiting for test results, which may take up to two days. Diagnostic tests focus on identifying the organism causing the illness. This process may involve performing a culture on contaminated material from the suspect food, a stool sample, or swabs of the nose or throat of the affected individual if inhaled spores are a possibility. Culture results are available from the microbiology laboratory as soon as bacteria grow in a special plate incubated at temperatures at or above body temperature. The growth of specific bacteria confirms the diagnosis. The microbiology laboratory may use samples of the bacteria grown to perform other special techniques to help identify the causative organism.

In infant botulism, the infant's stool may be cultured to isolate the organism; this test may be performed by the state health department or the Centers for Disease Control (CDC). Early diagnosis of botulism is critical so that treatment can begin in time to avoid neurological involvement. Although the definitive diagnosis comes from laboratory tests, it can usually be diagnosed by recognizing the distinctive neurological symptoms typical of contamination with C. botulinum.

While waiting for diagnostic test results, the doctor performs a physical examination and may ask about recently consumed food, possible open sores, recent activities and behavior, and other information that may help to rule out other disease possibilities. Imaging studies or additional diagnostic tests may be done to rule out other diseases or conditions with similar symptoms.

Many cases of food poisoning go undiagnosed, since a definite diagnosis is not necessary to effectively treat the symptoms. Because it takes time for symptoms to develop, the most recent food one has eaten may not be the cause of the symptoms.

Treatment

Treatment of food poisoning, except for botulism, focuses on preventing or correcting dehydration by replacing critical fluids and electrolytes lost through vomiting and diarrhea. Electrolytes are mineral salts that form electrically charged particles (ions) in body fluids; they help control body fluid balance and participate in many essential body functions. Pharmacists can recommend effective, pleasant-tasting, electrolyte replacement fluids that are available without a prescription. To prevent dehydration, a doctor may decide to give fluids intravenously. In very serious cases of food poisoning, medications may be given to stop abdominal cramping and vomiting. Antidiarrheal medications are not usually given. Stopping the diarrhea actually maintains toxin levels in the body for longer periods and may prolong the infection. Severe bacterial food poisonings are sometimes treated with intravenous antibiotics .

Modifying the diet while recovering from food poisoning is usually recommended. During a period of active vomiting and diarrhea, solid food should be avoided and only small quantities of clear liquids should be consumed as frequently as possible. Once active symptoms stop, bland, soft, easy-to-digest foods should be consumed for two to three days. One example is the BRAT diet of bananas, rice, applesauce, and toast, all of which are easy to digest. Milk products, spicy food, and fresh fruit should be avoided for a few days, although babies should continue to breastfeed. These modifications are often the only treatment that is necessary.

Botulism is treated in an entirely different way. Older children and adults can be treated with injections of a specific antitoxin for botulism if it can be administered within 72 hours after symptoms are first observed. If given later, it provides little or no benefit. Infants, however, cannot receive this antitoxin and are usually treated instead with injections of human botulism immune globulin (BIG), an antiserum that neutralizes the botulinum toxin. This antiserum is available in the United States through the Infant Botulism Treatment and Prevention Program in Berkeley, California. Both infants and adults may require hospitalization , often in the intensive care unit. Mechanical ventilators may be used for those whose ability to breathe is impaired and intravenous nutrition may be provided until any paralysis is corrected.

Alternative treatment

Alternative practitioners offer the same advice as traditional practitioners concerning diet modification, treatment of diarrhea and vomiting, and prevention of dehydration. Charcoal tablets, Lactobacillus acidophilus, Lactobacillus bulgaricus, and citrus seed extract can be taken to help normalize the digestive system. An electrolyte replacement fluid can be made at home by adding one teaspoon of salt and four teaspoons of sugar to one quart of water. For food poisoning other than botulism, two homeopathic remedies, either Arsenicumalbum or Nux vomica, are recommended to help reduce symptoms.

Prognosis

Most cases of food poisoning (except botulism) clear up on their own within one week without medical assistance. As symptoms subside, the individual may continue to feel tired or weak for a few days. If dehydration has been effectively corrected or prevented, few complications can be expected. Deaths are rare and usually occur in the very young, the very old, and people whose immune systems are already weakened.

Complications of salmonella food poisoning may include arthritis-like symptoms that occur three to four weeks after infection. Although deaths from salmonella infection are rare, they do occur. Most deaths reported have occurred among elderly adults in long-term care.

Adults usually recover from E. coli poisoning without medical intervention, but many children require hospitalization for contamination with this organism. Toxins may be absorbed into the blood stream where they destroy red blood cells and platelets, tiny cells important in blood clotting. About 5 percent of victims develop hemolytic-uremic syndrome (HUS), which can result in sudden kidney failure that requires a medical procedure (dialysis) to perform the kidney's task of filtering the body's waste products.

Botulism is the deadliest of the bacterial food-borne illnesses. With prompt medical care, the death rate is less than 10 percent in children and adults.

Prevention

Food poisoning is almost entirely preventable by practicing good sanitation and good food handling techniques. These include the following measures:

KEY TERMS

Antitoxin —An antibody against an exotoxin, usually derived from horse serum.

Culture —A test in which a sample of body fluid is placed on materials specially formulated to grow microorganisms. A culture is used to learn what type of bacterium is causing infection.

Diuretics —A group of drugs that helps remove excess water from the body by increasing the amount lost by urination.

Electrolytes —Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Hemolysis —The process of breaking down red blood cells. As the cells are destroyed, hemoglobin, the component of red blood cells which carries the oxygen, is liberated.

Lactobacillus acidophilus —Commonly known as acidophilus, a bacteria found in yogurt that changes the balance of the bacteria in the intestine in a beneficial way.

Neurological —Relating to the brain and central nervous system.

Neurotoxin —A poison that acts directly on the central nervous system.

Platelet —A cell-like particle in the blood that plays an important role in blood clotting. Platelets are activated when an injury causes a blood vessel to break. They change shape from round to spiny, "sticking" to the broken vessel wall and to each other to begin the clotting process. In addition to physically plugging breaks in blood vessel walls, platelets also release chemicals that promote clotting.

Spore —A dormant form assumed by some bacteria, such as anthrax, that enable the bacterium to survive high temperatures, dryness, and lack of nourishment for long periods of time. Under proper conditions, the spore may revert to the actively multiplying form of the bacteria. Also refers to the small, thick-walled reproductive structure of a fungus.

Toxin —A poisonous substance usually produced by a microorganism or plant.

• Keep hot foods hot and cold foods cold.
• Cook meat to the recommended internal temperature.
• Use a meat thermometer to check meat and cooking eggs until they are no longer runny.
• Refrigerate leftovers promptly, not letting food stand at room temperature.
• Before preparing other foods, carefully clean surfaces (cutting boards and counters, knives and other utensils) contaminated with the juices of uncooked meats.
• Do not refreeze meat once it has been thawed.
• Wash fruits and vegetables before using.
• Consume only pasteurized dairy products and fruit juices.
• Discard 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.

It is especially important to discard any food that seems spoiled and not to eat food that has been stored at room temperature or above for more than a few hours. Home canners must be diligent about using sterile equipment and following U.S. Department of Agriculture canning guidelines.

Infant botulism is perhaps the most difficult poisoning to prevent, because what goes into an infant's mouth is often beyond control. One important preventative measure, however, is to avoid feeding honey to infants younger than 12 months since it is a known source of botulism spores. As infants begin eating solid foods, the same food precautions should be followed as for older children and adults.

Parental concerns

Symptoms of food poisoning can appear as early as an hour after consuming the contaminated food or up to several days later. Parents may be concerned about possible contamination from unknown sources and that symptoms may occur suddenly, without warning. Practicing good sanitation and good food handling techniques is the best way parents can prevent contamination. Normal watchfulness of the parents is sufficient to notice symptoms, paying attention to any change in eating, unusual crying, increases or decreases in bowel movements, the presence of vomiting or a lack of normal responses such as turning of the head and body movements. An early report of symptoms, even if no particular food is suspected of causing illness, helps get early treatment and avoid complications.

See also Botulism; Gastroenteritis.

Resources

BOOKS

Cerexhe, Peter, et al. Risky Food, Safer Choices: Avoiding Food Poisoning. Boulder, Co: netLibrary, 2000.

Isle, Mick. Everything You Need to Know about Food Poisoning. New York: Rosen Publishing Group, 2001.

Rue, Nancy, and Anne Williams. Quick Reference to Food Safety and Sanitation. Boston, MA: Prentice Hall, 2002.

Trickett, Jill. The Prevention of Food Poisoning. Cheltenham, UK: Nelson Thornes, 2001.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: <www.cdc.gov>.

WEB SITES

"Food Safety." Available online at <www.nlm.nih.gov/medlineplus/print/foodsafety.html> (accessed November 20, 2004).

L. Lee Culvert Suzanne M. Lutwick, MPH

Food Poisoning

Definition

Description

Demographics

Causes and symptoms

Diagnosis

Treatment

Nutrition/Dietetic concerns

Prognosis

Prevention

Resources

Definition

Food poisoning comes from eating food or drinking water that is the contaminated with a virus, bacterium, parasite, or chemical that causes illness. It is also called gastroenteritis.

Description

Foodborne illness is a serious public health concern in the United States and around the world. More than 250 foodborne diseases have been identified. Most food poisoning is unpleasant but not severe enough to require professional medical treatment. However, the economic impact of food poisoning is substantial. The United States Centers for Disease Control (CDC) estimates that food poisoning costs the United States between 5 and 6 billion dollars annually in direct medical care and lost productivity.

The organisms and chemicals that cause food poisoning can contaminate food at any point during the production process. Animal products cause the majority of food poisonings. They can become contaminated during slaughter, processing, transport, storage, or preparation. A vegetarian diet, however, does not protect a person from food poisoning. Fruits and vegetables can be contaminated in the fields from animal feces or pesticides, as well as during harvesting, processing, distribution, and storage. The CDC estimates that about 97% of all food poisoning comes from improper food handling.Of that, 80% occurs from food prepared in businesses (e.g. restaurants or work cafeterias) or institutions (e.g. schools or jails). The remaining 20% occurs from food prepared at home. In the twenty-first century, American bioterrorism experts have become increasingly concerned that a disease-causing organism could intentionally be introduced into the food or water supply to cause a mass outbreak of food poisoning illness.

Demographics

The CDC estimates that about 76 million cases of food poisoning occur in the United States each year. The specific organism causing the disease is identified in only about 14 million cases. Most cases of food poisoning are mild, but about 325,000 individuals are hospitalized for food poisoning each year in the United States, and about 5,000 die. Internationally, food poisoning is about five times more common in developing countries than in the United States and Europe. In underdeveloped countries where contaminated water supplies are common and refrigeration is rare, foodborne illnesses may cause a billion illnesses and 4-6 million deaths each year.

Food poisoning is an equal opportunity illness. It affects people independent of race, age, or gender. However, the very young, the elderly, pregnant women, and people with weakened immune systems (e.g. people with HIV/AIDS, leukemia, transplant patients) are more likely to have severe cases that result hospitalization and life-threatening complications.

Causes and symptoms

Food poisoning can be divided into two basic types: illness caused by infectious organisms and illness caused by chemicals. The infectious organisms (pathogens) that cause food poisoning are bacteria, viruses, and parasites. Chemicals can be either natural toxins (poisons) found in plants (e.g. poisonous mushrooms) and animals (Japanese puffer fish) or they can be man-made chemicals such as pesticides or herbicides.

Symptoms of food poisoning usually develop anywhere within 1-48 hours after eating contaminated food. Symptoms of chemical food poisoning often appear very quickly. The type of symptoms and their severity depend on the cause of the food poisoning, the amount of contaminated food eaten, and the health of the individual. Symptoms usually develop suddenly. Some common symptoms of food poisoning include:

• nausea followed by forceful vomiting
• frequent diarrhea. Stools can be extremely watery and may or may not contain blood
• painful stomach cramps
• fever
• headache
• dizziness
• blurred vision, difficulty breathing, tingling in hands and feet (chemical food poisoning)

Microorganisms responsible for common food-borne illness

(Illustration by GGS Information Services/Thomson Gale.)

Contamination that causes food poisoning can occur at every level of the food production process Some examples follow.

• Growers: application of illegal pesticides and herbicides or their application higher than approved concentrations. In the United States, pesticides use is regulated by the United States Department of Agriculture (USDA) and the Environmental Protection Agency (EPA)
• Processors: use of contaminated water in processing, inadequate disinfecting of processing equipment, inadequate time and temperature in processing canned or cooked foods, contamination with poisons used to control factory pests, and improper handling of raw materials. In the United States, meatpacking plants are inspected by the USDA, and other food processing plants are inspected by the United States Food and Drug Administration (FDA)
• Storage and transportation: holding fresh or frozen foods at improper temperatures, inappropriate use of fumigants in warehouses or trucks, inadequate sanitizing of food-carrying tanker trucks (e.g. milk, corn syrup), and contamination by insects or rodent droppings in storage areas
• Retail outlets and restaurants: food kept at improper temperatures, cross-contamination between raw and cooked food, improper disinfecting of food preparation surfaces, transmission by infected food handlers,

KEY TERMS

Pathogen —An organism that causes a disease.

Toxin —A general term for something that harms or poisons the body.

and failure of food handlers to wash their hands. Restaurants are inspected by local health authorities.

• Home preparation: letting food sit out too long at room temperature, inadequate cooking, cross-contamination between cooked and raw food, failure to properly reheat leftovers

Bacteria

Bacterial contamination is the leading cause of food poisoning. At room temperature, bacteria reproduce at astounding rates. A single bacterium that divides every half hour can produce 17 million offspring in 12 hours. Bacteria fall into two general categories. One group causes symptoms of food poisoning by directly infecting the intestines causing irritation and diarrhea. The other group release toxins (poisons) as they grow and reproduce. These toxins affect the digestive system and often cause vomiting first followed by diarrhea. Many bacteria cause food poisoning. A few of the more common ones are described below.

Bacteria of the genus Salmonella are common in reptiles, birds, and mammals. They are found most often in eggs, poultry, dairy products, and beef. Infection with Salmonella causes nausea, vomiting, stomach cramps, headache, and low-grade fever. Symptoms begin anywhere from 6 to 48 hours after exposure and may last for 7 days. In people with weakened immune systems, Salmonella

Bacteria of the genus Campylobacter cause more diarrhea illnesses worldwide than any other group of bacteria. They produce fairly mild diarrhea, fever, and stomach cramps. Campylobacter bacteria are found in almost all raw chicken and turkey. Cross-contamination, that is putting cooked food down where raw food had been, is a leading cause of food poisoning from Campylobacter These bacteria are also transmitted by water contaminated with animal feces.

Escherichia coli are a large group of bacteria, only some of which cause food poisoning. E. coli food poisoning usually begins with watery diarrhea that later turns bloody. One strain of E. coli known as 0157:H7 is most often found in undercooked hamburger, but has also been found in ready-to-eat raw spinach. This particular strain can cause kidney failure and death, especially in children and the elderly.

Clostridium botulinium is a bacteria that causes the disease botulism. C. botulinium produces a toxin that affects the nervous system and can cause difficulty breathing and paralysis. Symptoms do not appear until 1 to 4 days after exposure. Botulism is associated with improperly canned food, smoked fish, and honey. Infection with C. botulinium is serious and often fatal.

Viruses

A large group of viruses called Norwalk or Nor-walk-like viruses are an extremely common cause of foodborne illness. In the mid-2000s, Norwalk viruses were often in the news for causing outbreaks of gastrointestinal disease on cruise ships and in nursing homes. They cause more vomiting than diarrhea than any other viruses. Unlike many of the other causes of food poisoning, these viruses are not usually naturally present in food. They are usually transferred from the hands of infected food handlers to the food that they are preparing, especially to foods such as salads and sandwiches.

Parasites

Parasites that cause food poisoning usually come from contaminated water. They often cause mild symptoms that are slow to develop but last for several weeks. Giardia causes watery diarrhea and is often acquired by drinking untreated water from lakes or streams. Cyrptosporidium is a parasite that causes large amounts of watery diarrhea for 3–4 days. Healthy people usually recover quickly, but in people with weakened immune systems, symptoms can persist for a long time.

Natural toxins

Natural poisons found in some wild mushrooms can cause anything from nausea and vomiting to hallucinations, coma, and death, depending on the amount and species of mushroom eaten. Mushroom poisoning is a medical emergency. People who believe they have eaten a poisonous mushroom should, if possible, take a sample of the mushroom or their vomit to the emergency room with them. Identifying the type of mushroom causing the illness can help determine the most effective treatment.

Oysters, clams, mollusks, and scallops can contain toxins that affect the nervous system. Symptoms usually begin with a tingling in the mouth, then the arms and legs. Individuals may become dizzy and may have difficulty breathing. Shellfish poisoning is a medical emergency because the muscles needed for breathing may become paralyzed. Similar symptoms result from eating the Japanese puffer fish which contains a natural poison that in its skin and digestive system that affects the nervous system.

Manmade toxins

Manmade toxins include all pesticides, fertilizers, disinfectants, and any other chemicals remaining in food when it is eaten that can cause illness. Contamination is accidental, and often the result of ignorance or a misunderstanding of how to apply the chemical. Symptoms may develop rapidly or slowly depending on the type of chemical and the amount of exposure. Chemical poisoning requires prompt medical evaluation.

Diagnosis

Food poisoning is caused by many different organisms, but identifying the exact organism is not usually necessary. Most mild food poisoning is diagnosed by the symptoms of vomiting, diarrhea, and stomach cramps coupled with information about that the individual has recently eaten. The length of time between eating the suspect food and the start of symptoms gives physicians a clue about what particular organism may be causing the food poisoning. Blood and urine tests may be ordered to determine the individual’s degree of dehydration and electrolyte (chemical) imbalances. In most cases, determining the exact pathogen that is causing the food poisoning is relatively unimportant, as treatment tends to be the similar for most causes. However, if diarrhea is persistent, a stool culture may be done to provide more specific information.

When chemical or natural toxin poisoning is suspected, determining the exact cause is more important, and treatment is specific to the cause. The stomach may be pumped and the contents tested. Extensive blood tests are usually needed. Sometimes activated charcoal is used to help absorb the poison in the stomach.

Treatment

The main goal of treatment for food poisoning is to keep the individual from becoming dehydrated. A loss of 20% of a person’s body fluid is fatal, and 10-15% is serious. In food poisoning, huge amounts of both water and electrolytes can be lost quite rapidly. Vomiting and diarrhea in infants and young children require especially prompt professional treatment because small children can become dehydrated within hours.

Mild cases of food poisoning can usually be treated at home, especially if they are not accompanied by a fever. Dehydration in infants and children can be prevented or treated by giving them oral rehydration solutions such as Pedialyte, Infalyte, Naturalyte, Ora-lyte, or Rehydralyte. These are available in supermarkets and pharmacies without a prescription. Oral rehydration solutions have the proper balance of salts and sugars to restore fluid and electrolyte balance. They can be given to young children in small sips as soon as vomiting and diarrhea start. Children may continue to vomit and have diarrhea, but some of the fluid will be absorbed. In the past, parents were told to withhold solid food from children who had diarrhea. New research indicates that it is better for children should to be allowed to eat solid food should they want it, even though diarrhea continues.

Older children and adults who are dehydrated can be given oral rehydration solutions or sports drinks such as Gatorade. Adults and older children with food poisoning should avoid drinking coffee, tea, and soft drinks, especially soft drinks that contain caffeine , as these liquids promote dehydration. Over-the counter medications to stop or slow diarrhea such as Kaopectate, Pepto-Bismol, or Imodium will not shorten the duration of the disease, but may give the individual some control over his or her bowels. Consult a physician before giving these over-the-counter medicines to children.

Individuals of all ages who are seriously dehydrated need to be treated promptly by a medical professional. In the case of severe dehydration, the individual may be hospitalized and fluids given intravenously (IV; directly into the vein). Drugs may also be prescribed to stop persistent vomiting. Although bacteria cause many cases of food poisoning, antibiotics are not routinely used in treatment. Some studies have shown that antibiotics are necessary only in about 10% of cases.

Individuals who think their food poisoning symptoms are caused by chemicals or natural toxins should seek emergency medical care immediately. These types of food poisoning are too serious to try to treat at home.

Nutrition/Dietetic concerns

Certain foods are more commonly associated with food poisoning than others. These include:.

• raw and undercooked meat, especially ground meat
• raw or undercooked poultry
• raw or undercooked eggs and egg products such as mayonnaise or raw cookie dough. Estimates are that 1 of every 20,000 eggs is contaminated with Salmonella
• unpasteurized milk products or unpasteurized fruit juice
• raw shellfish, especially oysters, clams, scallops, and mussels
• ready-to-eat raw fruits and vegetables
• alfalfa and bean sprouts
• wild mushrooms. Note: many mushrooms that are poisonous in North America look almost identical to safe-to-eat mushrooms found in Europe
• improperly prepared fish such as barracuda or Japanese puffer fish
• improperly canned foods (homemade or commercial). Note: any can that is leaking or bulging should be discarded
• soft cheeses such as brie or feta
• lunch meats or deli meats

Although the food in the United States is very safe, occasionally major outbreaks of food poisoning occur that can be traced to a breakdown in the food handling system. Larger outbreaks can be identified and traced to their source because each state has a list of diseases that health professionals are required to report to the county public health service once positive diagnosis is made. Most states require that doctors and hospitals report confirmed cases of disease caused by Salmonella and E. coli 0157:H7 and several other food poisoning pathogens. This information is then passed on to the CDC.

Most food poisoning occurs to single individual or to a small group of people, such as a family at a picnic. A major food poisoning outbreak is suspected when many people develop the same symptoms of food poisoning within a short time or within the same geographic area. A major outbreak sets off a full investigation by a team of microbiologists, food scientists, process engineers, specialists in food sanitation, and others. In a larger outbreak, the CDC usually coordinates the investigation. The CDC has established a special system called FoodNet to monitor food poisoning reports and look for patterns that suggest an outbreak. Information on chemical and natural toxin poisonings is also collected by the American Association of Poison Control Centers.

Prognosis

Most people have unpleasant gastrointestinal symptoms—vomiting and diarrhea—for a few days and then recover fully from food poisoning. In young children, dehydration is always a cause for concern. Worldwide, dehydration from diarrhea is the biggest killer of children under age 5. If dehydration can be controlled in young children with food poisoning, most recover with few complications. However, E. coli 0157:H7 can cause fatal renal failure in 3-5% of children. This bacteria is most often acquired by eating unpasteurized apple cider or apple juice, alfalfa or bean sprouts.

More serious long-term health problems often result from chemical poisonings. Toxins found in some wild mushrooms and some fish can cause permanent liver damage requiring a liver transplant or death. Pesticides and other chemical contamination can cause liver damage, kidney failure, and nervous system complications. In 2007, apparent chemical contamination of pet food caused the death of hundreds of dogs and cats in the United States.

Prevention

Appropriate food handling procedures at every level of the production process can go a long way in preventing food poisoning. Growers should apply only approved pesticides and herbicides at levels recommended by the Environmental Protection Agency and the Department of Agriculture. Processors must use clean sources of water to wash produce. Processing machinery must be disinfected regularly, and pesticides used in processing plants must be safe for use around food. In restaurants, food must not be held under warming lights of on buffet tables for long periods.

At home, individuals can help prevent food poison by following these guidelines.

• Wash hands, food preparation surfaces, and utensils often when handling food
• Prevent cross-contamination of raw and cooked food. Do not put cooked food back on the same plate or surface that held it when it was raw
• Cook foods to internal temperatures between 140°F and 180°F (60-83° C)
• Refrigerate or freeze fresh foods and leftovers promptly
• Defrost food in the refrigerator or microwave and not on the counter at room temperature. Cook promptly when defrosted
• Keep food at temperatures above 140°F (60°C) or below 40°F (4° C)
• Throw out food that has sat at room temperature for 2 hours or more

Resources

BOOKS

Bjorklund, Ruth. Food Borne Illnesses New York : Marshall Cavendish Benchmark, 2006.

Scott, Elizabeth and Paul Sockett. How to Prevent Food Poisoning: A Practical Guide to Safe Cooking, Eating, and Food HandlingNew York: Wiley, 2001.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Road, Atlanta, GA. 30333. Telephone: (800) 311-3435 or (404) 639-3534. Website: <http://www.cdc.gov>.

National Digestive Diseases Information Clearinghouse (NDDIC). 2 Information Way Bethesda, MD 20892-3570. Telephone: (800) 891-5389. Fax: (703) 738-4929. Website: <http://digestive.niddk.nih.gov>.

United States Food and Drug Administration (FDA), Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements. 5100 Paint Branch Parkway, College Park, Maryland 20740. Fax: 301-436-2639. Website: <http://www.cfsan.fda.gov/~dms/onplds.html>.

United States Department of Agriculture. Gateway to Government Food Safety Information. Website: <http://www.foodsafety.gov/>.

OTHER

Centers for Disease Control and Prevention “Foodborne Illness.” October 25, 2005. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm>.

Cunha, John P. “Food Poisoning.” eMedicineHealth.com, August 10, 2005. <http://www.emedicinehealth.com/food_poisoning/article_em.htm>.

Gammara, Roberto and David M. Manuel. “Food Poisoning.” eMedicine.com, January 2, 2007. <http://www.emedicine.com/med/topic.870htm>.

Mayo Clinic Staff. “8 Ways to Prevent Food Poisoning at Home.” MayoClinic.com, June 14, 2006. <http://www.mayoclinic.com/health/food-safety/NU00291>.

Medline Plus. “Food Contamination and Poisoning.” U. S. National Library of Medicine, April 3, 2007. <http://www.nlm.nih.gov/medlineplus/foodcontaminationandpoisoning.html>.

Medline Plus. “Food Poisoning.” U. S. National Library of Medicine, April 5, 2007. <http://www.nlm.nih.gov/medlineplus/ency/article/001652.htm>.

National Digestive Diseases Information Clearinghouse. “Bacteria and Foodborne Illness.” October 2003. <http://digestive.niddk.nih.gov/ddiseases/pubs/bacteria>.

Sood, Sunil K. “Food Poisoning.” eMedicine.com, June 20, 2006. <http://www.emedicine.com/ped/topic795.htm>.

Tish Davidson, A.M.

Food pyramid seeUSDA Food Guide Pyramid (MyPyramid).

Food poisoning

Definition

Food poisoning is a general term for health problems arising from eating food contaminated by viruses, chemicals, or bacterial toxins. Types of food poisoning include bacterial food poisoning, shellfish poisoning, and mushroom poisoning. The medical term for food poisoning is gastroenteritis .

Description

The Centers for Disease Control and Prevention (CDC) estimates that there are up to 33 million cases of food poisoning in the United States each year. Many cases are mild, and they pass so rapidly that they are never diagnosed. Occasionally, a severe outbreak creates a newsworthy public health hazard, but these instances are rare. Anyone can get food poisoning, but the very young, the very old, and those with compromised immune systems have the most severe and life-threatening cases.

Causes & symptoms

General indications of food poisoning include diarrhea, stomach pain or cramps, gurgling sounds in the stomach, fever, nausea , and vomiting . Dehydration is a common complication, since fluids and electrolytes are lost through vomiting and diarrhea. Dehydration is more

likely to happen in the very young, the elderly, and people who are taking diuretics.

Bacterial sources of food poisoning

Bacteria are major causes of food poisoning. Symptoms of bacterial food poisoning occur because foodborne bacteria release enterotoxins, or poisons, as a byproduct of their growth in the body. These toxins often diminish the absorptive ability of the intestines and cause the secretion of water and electrolytes that leads to dehydration. The severity of symptoms depends on the type of bacteria, the amount of bacteria and food consumed, and the individual's health and sensitivity to the bacteria's toxin.

SALMONELLA. Symptoms of poisoning begin 12–72 hours after eating food contaminated with Salmonella. Classic food poisoning symptoms, including fever, occur for about two to five days. Salmonella is usually transmitted through the consumption of food contaminated by human or other animal feces. This contamination is mostly due to lack of hand washing by food handlers.

ESCHERICHIA COLI (E. COLI ). Symptoms of food poisoning from E. coli 0157:H7 and similar strains of E. coli are slower to appear than those caused by some of the other foodborne bacteria. One to three days after eating contaminated food, the victim begins to have severe abdominal cramps and watery diarrhea that usually becomes bloody. The diarrhea may consist mostly of blood and very little stool, so the condition is sometimes called hemorrhagic colitis. There is little or no fever, the bloody diarrhea lasts from one to eight days, and the condition usually resolves by itself. Food contamination from E. coli O157:H7 has mostly been found in raw or undercooked ground beef. Raw milk has also been a source of food poisoning by E. coli.

CAMPYLOBACTER JEJUNI. C. jejuni infections are most often caused by contaminated chicken, but unchlorinated water and raw milk may also be sources of infection. Classic symptoms of food poisoning, including fever and diarrhea, begin two to five days after consuming food or water contaminated with C. jejuni. The diarrhea may be watery and may contain blood. Symptoms last from seven to 10 days, and relapses occur in about one quarter of the people who are infected.

STAPHYLOCOCCUS AUREUS (STAPH). Staph is spread primarily by food handlers with Staph infections on their skin. However, contaminated equipment and food preparation surfaces may also be at fault. Almost any food can be contaminated, but salad dressings, milk products, cream pastries, and food kept at room temperature, rather than hot or cold, are likely candidates. Classic symptoms of food poisoning appear rapidly, usually two to eight hours after the contaminated food is eaten. Such symptoms usually last only three to six hours and rarely more than two days. Most cases are mild and the victim recovers without any assistance.

SHIGELLA. Symptoms of food poisoning by Shigella appear 36–72 hours after eating contaminated food. These symptoms are slightly different from those associated with most foodborne bacteria. In addition to the familiar symptoms of food poisoning, up to 40% of children with severe infections show neurological symptoms. These include seizures, confusion, headache , lethargy, and a stiff, sore neck. The disease runs its course in two to three days.

CLOSTRIDIUM BOTULINUM. C. botulinum (commonly known as botulism) is the deadliest of the bacterial foodborne illnesses. Sources for adult botulism are

often improperly canned or preserved food. Symptoms of adult botulism appear about 18 to 36 hours after the contaminated food is eaten, although there are documented times of onset ranging from four hours to eight days. Unlike other foodborne illnesses, there is no vomiting and diarrhea associated with botulism. Initially, a person suffering from botulism feels weakness, dizziness , and double vision. Symptoms progress to difficulty with speaking and swallowing. The toxins from C. botulinum are neurotoxins—they poison the nervous system, causing paralysis. If the disease proceeds unchecked, paralysis will move throughout the body. Eventually, without medical intervention, the respiratory muscles will become paralyzed and the victim will suffocate.

With infant botulism, the spores of C. botulinum lodge in the infant's intestinal tract. Honey, especially when consumed by infants younger than 12 months, is sometimes the source of these spores. Onset of the symptoms is gradual. The infant initially has constipation , followed by poor feeding, lethargy, weakness, drooling, and a distinctive wailing cry. Eventually the baby loses the ability to control its head muscles. Paralysis then progresses to the rest of the body.

Fish-associated food poisoning

Ciguatera fish poisoning is caused by toxins accumulated in the tissues of certain tropical fish, including groupers, barracudas, snappers, and mackerel. Signs of poisoning occur about six hours after eating the fish. Around the mouth, there may be numbness and tingling, which may spread to other places including the hands and feet. There is often muscle pain and weakness, headache, dizziness, joint pain, sensitivity to temperature, heart arrhythmias, dramatic changes in heart rate, and reduced blood pressure. Reef fish contaminated with ciguatoxin are being exported all over the world, occurrence of ciguatera is becoming more likely in colder climates.

Pufferfish, or fugu, is a traditional gourmet dish served mostly in Japan. The skin and other organs of the pufferfish contain a strong poison called tetradotoxin. The first stage of tetradotoxin poisoning is indicated by numbness of the lips and tongue, which may occur 20–180 minutes after eating the fish. This is followed by tingling and numbness of the face, hands, and feet. Classic symptoms of food poisoning are accompanied by other neurological symptoms such as light-headedness, headache, and unsteady gait. The second stage of tetradotoxin poisoning brings on a progressive paralysis. Breathing, talking, and other movement becomes difficult. Cyanosis (bluish or purplish skin discoloration), low blood pressure, and arrhythmias may occur. Convulsions and mental impairment may happen right before death, or the person may be completely lucid, though unmoving. Death usually occurs four to six hours after ingestion of the fish if there is no proper intervention; that time, however, has been known to be as little as 20 minutes.

Shellfish poisoning is caused by toxins made by certain algae eaten by shellfish. The toxins are then accumulated in the bodies of the shellfish. Cockles, mussels, clams, oysters, and scallops are most often affected. Sometimes the toxin-producing algae multiply to such an extent that they cause the waters they live in to take on the reddish color of their bodies. This phenomenon is known as a red tide. Warnings are often given against eating shellfish from such areas. Symptoms of food poisoning show up within a half an hour to two hours of eating the

shellfish, depending on the amount and type eaten. There may be burning and tingling in the face and mouth, numbness, drowsiness, muscular pain, dizziness, diarrhea, stomachache, confusion, nausea, vomiting, odd temperature sensations, difficulty breathing, and possibly coma. The symptoms may last from a few hours to a few days.

Histamine poisoning can occur from eating fish whose body tissues have begun to produce high levels of histamine. Mackerel, tuna, and mahi mahi are most often the sources. After consumption of the fish, immediate facial flushing and hives may occur, as well as classic symptoms of food poisoning becoming evident a few minutes later. Symptoms usually last less than 24 hours.

Mushroom poisoning

Mushroom poisoning is classified by the effects of the poisons. Protoplasmic poisons result in cell destruction, often in the liver, which progresses to complete organ failure. Neurotoxins cause neurological symptoms such as sweating, convulsions, hallucinations, excitement, depression , coma, and colon spasms. Gastrointestinal (G/I) irritants rapidly bring on the classic symptoms of food poisoning and then resolve just as quickly. Disulfiram-like poisons are generally nontoxic, except when alcohol is consumed within 72 hours of eating them. In these cases, the poisons cause headache, nausea, vomiting, flushing, and cardiac disturbances for two to three hours.

Other possible sources

Other possible sources of food poisoning include ingestion of green or sprouting raw potatoes, ingestion of fava beans by susceptible persons, and ergot poisoning from ingestion of contaminated grain. Chemical contaminant food poisoning may result from the ingestion of unwashed produce sprayed with arsenic, lead, or insecticides. Food served or stored in lead-glazed pottery cadmium-lined containers may also lead to food poisoning.

Diagnosis

An important aspect of diagnosing food poisoning is the clinical interview. A history of the illness should be thoroughly traced to include ingestion of food, recent travel, and contact with those showing similar symptoms of illness. Because it may take 30 minutes to three days for symptoms to develop, it is not necessarily the most recent food eaten that is the cause of the symptoms. Diagnosis is confirmed with a stool culture. Other laboratory tests may be used to examine vomitus, blood, or the contaminated food. A blood chemistry panel may be performed to determine the extent of any tissue damage or electrolyte imbalances. Many cases of food poisoning go undiagnosed, and treatment focuses on the short-lived G/I symptoms.

Botulism is usually diagnosed from its distinctive neurological symptoms, since rapid treatment is essential to save the patient's life. Electromyography, a test analyzing the electrical activity of muscles, may later be done to further confirm diagnosis. The test shows abnormal muscle activity in most cases of botulism.

Treatment

Those suffering from food poisoning should reduce all sugar and normal food for eight to 24 hours, and increase fluids to avoid dehydration. Charcoal tablets, Lactobacillus acidophilus, Lactobacillus bulgaricus, and citrus seed extract are all recommended. For mild cases of food poisoning, the homeopathic remedies Arsenicum album, Veratrum album, Podophyllum, or Nux vomica are recommended. The remedy should be given in 12c potency every three to four hours until symptoms subside. If a ready-made electrolyte replacement is not available, a homemade one can be made by dissolving exactly 1 tsp (5 ml) of salt and 4 tsp (20 ml) of sugar in 1 qt (1 l) of water.

Cinnamon (Cinnamonum zeylanicum), cloves (Syzigium aromaticum), oregano (Origanum vulgare ), and sage (Salvia officinalis ) are food herbs that are also strong inhibitors of bacteria. Liberal amounts can be added to foods, especially when traveling. Grapefruit seed extract has a natural antibiotic effect and may be of help. Large amounts of garlic , in food and in supplement form, are also recommended for the same reason.

Allopathic treatment

In serious cases of food poisoning, medications may be given to stop abdominal cramping and vomiting. Medications are not usually given for the diarrhea, since stopping it might keep toxins in the body longer and prolong the illness. Severe bacterial food poisonings are sometimes treated with antibiotics, but their use is controversial. Washing out the stomach contents to remove the toxic substances may be required. This procedure is called gastric lavage, familiarly known as having the stomach pumped. Neurotoxins often interfere with the breathing process. If the ability to breathe is affected, patients may have to be put on a mechanical ventilator to assist their breathing and are fed intravenously until the paralysis passes.

People who show any signs of botulism poisoning must receive immediate emergency medical care. Both infants and adults suffering from food poisoning by C. botulinum require hospitalization, often in the intensive care unit. A botulism antitoxin is given to adults, if it can be administered within 72 hours after symptoms are first observed. If given later, it provides no benefit. Nasogastric intubation is recommended for the feeding of infants with active botulism. As well as supplying nutrition , it will stimulate peristalsis, helping in the elimination of C. botulinum.

Treatment of food poisoning that is usually not an emergency situation may include drugs such as ipecac syrup to induce vomiting or laxatives to empty the intestines. Intravenous fluids containing salts and dextrose may be given to correct dehydration and electrolyte imbalances. Pain medications are given for severe stomach pain. Atropine is given for muscarine-type mushroom poisoning. If illness comes on after eating unidentified mushrooms, vomiting should be induced immediately, and the vomitus saved for laboratory testing. Intravenous mannitol is sometimes used to treat severe ciguatera poisoning. Antihistamines may be effective in reducing the symptoms of histamine fish poisoning. In 2001, Japanese scientists made a synthetic version of ciguatoxin, an important step in developing an antibody to help diagnose ciguatera.

In mild cases of food poisoning, dietary modifications are often the only treatment necessary. During periods of active vomiting and diarrhea, people with food poisoning should avoid solid food for eight to 24 hours, and should increase fluids. Clear liquids should be consumed in small quantities. Once active symptoms stop, a diet of bland, easily digested foods such as broth, eggs, rice and other cooked grains, and toast is recommended

for two to three days. Milk products, spicy food, alcohol, sweets, raw vegetables, and fresh fruit should be avoided.

Expected results

Many cases of food poisoning clear up on their own within a week without medical assistance. There are usually few complications once possible dehydration has been addressed. Fatigue may continue for a few days after active symptoms stop, however. In the more severe types of poisoning, especially those involving neurotoxins, the respiratory muscles may become paralyzed. In such cases, death will result from asphyxiation unless there is medical intervention. Deaths due to food poisoning are rare and tend to occur in the very young, the very old, and in people whose immune systems are already weakened.

C. botulinum, is likely to cause serious illness or fatalities, even when ingested in very small quantities. Children affected by food poisoning from E. coli often need to be hospitalized. In some cases, E. coli toxins may be absorbed into the blood stream where they destroy red blood cells and platelets, which are important in blood clotting. About 5% of victims, regardless of age, develop hemolytic uremia syndrome, which results in kidney failure.

Prevention

Eighty-four percent of adults surveyed in 2001 were unaware that feces on beef and poultry was the main carrier of salmonella, campylobacter, and E. coli. Other than informing the public, food poisoning prevention efforts include:

• hot foods should be kept hot, and cold foods should be kept cold
• meat should be cooked to the recommended internal temperature; eggs should be cooked until no longer runny
• leftovers should be refrigerated promptly and food should never be left to stand at room temperature
• contact of utensils and surfaces with the juices of raw meats should be avoided
• fruits and vegetables should be washed before using
• unpasteurized dairy products and fruit juices should be avoided
• bulging or leaking canned foods or any food that smells spoiled should be discarded
• hands should be washed with soap before food preparation and after using the bathroom
• food preparation surfaces should be sanitized regularly
• infants under 12 months should not be fed honey, which may contain spores of C. botulinum
• proper canning and adequate heating of home-canned food before serving are essential (boiling for three minutes is recommended)

Taking Lactobacillus acidophilus or L. bulgaricus may help prevent food poisoning, especially when traveling. Populating the intestines with these bacteria will make it less likely that harmful bacteria are able to gain a foothold.

Resources

PERIODICALS

"Chicken and Beef are Often Contaminated with Feces." Health and Medicine Week (October 1, 2001).

Ramsay, Sarah. "Organic Chemistry Takes on Tropical Seafood Poisoning." The Lancet (December 1, 2001): 1878.

OTHER

FDA Center for Food Safety & Applied Nutrition. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook. [cited October 2002]. <http://vm.cfsan.fda.gov/~mow/intro.html>.

Merck & Co., Inc. "E. coli O157:H7 Infection." The Merck Manual Online. [cited October 2002]. <http://www.merck.com/pubs/mmanual/section3/chapter28/28b.htm>.

Merck & Co., Inc. "Gastroenteritis." The Merck Manual Online. [cited October 2002]. <http://www.merck.com/pubs/mmanual_home/sec9/106.htm>.

Patience Paradox

Teresa G. Odle

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 coli O157: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.

Food Poisoning: Words to Know

C. botulinum:

A very deadly bacteria that causes a disease known as botulism.

Campylobacter jejuni (C. jejuni ):

A bacteria that is the leading cause of bacterial diarrhea in the United States. It occurs in healthy cattle, chickens, birds, and flies.

Electrolytes:

Salts and minerals present in the body that produce electriallcy charged particles (ions) in body fluids. Electrolytes control the fluid balance in the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Escherichia coli (E. coli ):

A bacteria that commonly causes food poisoning, most often from food products derived from cows, especially ground beef.

Platelets:

Blood cells needed to help blood clot.

Salmonella:

A bacteria that commonly causes food poisoning, most often from poultry, eggs, meat, and milk.

Shigella:

A bacterium that grows well in contaminated food and water, in crowded living conditions, and in areas with poor sanitation. It is transmitted by direct contact with an infected person or with food that has been contaminated by an infected person.

Staphylococcus aureus:

A bacteria that causes food poisoning, commonly found on foods that are kept at room temperature.

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

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.

FOOD IRRADIATION

Many methods for preserving food are available. These methods include freezing, drying, and canning. A method that may become more popular in the future is irradiation.

Irradiation is a process by which food is bombarded with high-energy radiation, such as X rays. This radiation kills bacteria in the food. Studies have shown that food irradiation is at least as effective as other methods of food preservation. For example, pork that is irradiated remains safe to eat for about ninety days. Pork kept under refrigeration is safe for no more than about forty days.

Today, the most common method for irradiating foods is with radioactive isotopes, such as cobalt 60 and cesium 137. Radioactive isotopes are materials that break apart and give off highenergy radiation.

Many people worry about the use of irradiation for preserving food. They fear that food may become radioactive and unsafe to eat. Or they worry that radiation may affect the taste, texture, or nutritional value of food.

Food irradiation is not a new technique. It has been used in other parts of the world for many years. The Food and Drug Administration (FDA) has given approval for the use of food irradiation in about a dozen kinds of foods. Whether that list becomes much longer remains to be seen.

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.

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.

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).

Food Poisoning

Definition

Food poisoning is a general term for health problems arising from eating contaminated food. Food may be contaminated by bacteria, viruses, environmental toxins, or toxins present within the food itself, such as the poisons in some mushrooms. Symptoms of food poisoning usually involve the prompt onset of vomiting and diarrhea. Some toxins also affect the nervous system.

Description

Every year millions of people suffer from bouts of vomiting and diarrhea that they blame on "something I ate." These people are generally correct. The Centers for Disease Control and Prevention (CDC) estimates that there are from six to 33 million cases of food poisoning in the United States each year. Many cases are mild and pass so rapidly that they are never diagnosed. Occasionally a severe outbreak creates a newsworthy public health hazard.

Classical food poisoning, sometimes incorrectly called ptomaine poisoning, is caused by a variety of different bacteria. The most common are Salmonella, Staphylococcus aureus, Escherichia coli O157:H7, Shigella, and Clostridium botulinum. Each has a slightly different incubation period and duration, but all except C. botulinum cause inflammation of the intestines and diarrhea. Sometimes food poisoning is called bacterial gastroenteritis or infectious diarrhea. Food and water can also be contaminated by viruses (cholera, rotavirus), environmental toxins (heavy metals), and poisons produced within the food itself (mushroom poisoning or fish and shellfish poisoning).

Careless food handling creates conditions for the growth of bacteria that make people sick. Food can become 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 soil, water, and dust during washing and packing. Home canned and commercially canned food may be improperly processed at too low a temperature or for too short a time to kill the bacteria.

Raw meats carry many foodborne bacterial diseases. The United States Food and Drug Administration (FDA) estimates that 90% or more of raw poultry sold at retail carry some disease-causing bacteria. Other raw meat products and eggs are contaminated to a lesser degree. Thorough cooking kills the bacteria and makes the food harmless. However, properly cooked food can become recontaminated if it comes in contact with plates, cutting boards, counter tops, or utensils that were used with raw meat and not cleaned and sanitized.

Cooked foods can also be contaminated after cooking by bacteria carried by food handlers or from bacteria in the environment. It is estimated that 50% of healthy people have the bacterium Staphylococcus aureus in their nasal passages and throat, as well as on their skin and hair. Rubbing a runny nose, then touching food can introduce the bacteria into cooked food. Bacteria flourish at room temperature and will rapidly grow into quantities capable of making people sick. To prevent this growth, food must be kept hot or cold, but never just warm.

Although the food supply in the United States is probably the safest in the world, anyone can get food poisoning. Serious outbreaks are rare. When they occur, the very young, the very old, and those with immune system weaknesses have the most severe and life-threatening cases. For example, this group is 20 times more likely to become infected with the Salmonella bacterium than the general population.

Travel outside the United States to countries where less attention is paid to sanitation, water purification, and good food handling practices increases the chances that a person will get food poisoning. People living in institutions such as nursing homes are also more likely to get food poisoning.

Rotavirus is the most common cause of severe diarrhea in children and accounts for the hospitalization of an estimated 55,000 children in the United States and over 600,000 deaths of children worldwide per year.

Other less common but serious food-borne illnesses may arise from consuming animals infected with bovine spongiform encephalopathy. Bovine spongiform encephalopathy (BSE) is a degenerative disorder affecting the central nervous system in cattle. It is also commonly referred to as "mad cow disease." BSE results from an "unconventional transmissible agent" which is yet to be determined precisely but is thought to be a pathogenic protein. Cell death leads to holes in the brain, creating a "sponge-like" consistency that results in the animal's death. As of 2005, there were more than 177,500 cases of BSE confirmed in the United Kingdom (UK). Only a few cases have been reported in the United States, where the food supply has been monitored closely. Imports of ruminants (suborder of mammals that includes sheep) and ruminant products have been restricted to some degree from countries where BSE was reported and has extended to all European countries. BSE is believed to be linked to a new variation of Creutzfeldt-Jakob disease (CJD) in humans, which is a progressive neurological disorder that can lead to death.

Causes and symptoms

The symptoms of food poisoning occur because foodborne bacteria release toxins or poisons as a byproduct of their growth in the body. These toxins (except those from C. botulinum) cause inflammation and swelling of the stomach, small intestine and/or large intestine. The result is abdominal muscle cramping, vomiting, diarrhea, fever, and the chance of dehydration. The severity of symptoms depends on the type of bacteria, the amount consumed, and the individual's general health and sensitivity to the bacterial toxin.

Salmonella

According to the CDC, approximately 1.4 million cases of Salmonella contamination occur annually in the United States, with about 40,000 being culture-confirmed cases reported to the CDC. Salmonella is found in egg yolks from infected chickens, in raw and undercooked poultry and in other meats, dairy products, fish, shrimp, and many more foods. The CDC estimates that one out of every 50 consumers is exposed to a contaminated egg yolk each year. However, thorough cooking kills the bacteria and makes the food harmless. Salmonella is also found in the feces of pet reptiles such as turtles, lizards, and snakes.

About one out of every 1,000 people get food poisoning from Salmonella. Of these, two-thirds are under age 20, with the majority under age nine. Most cases occur in the warm months between July and October. Salmonella poisoning manifests itself as salmonellosis, mostly caused by Salmonella enteritidis and Salmonella typhimurium. The incidence of salmonellosis has increased dramatically during the last two decades, due in part to the growing popularity of pet iguanas.

Symptoms of food poisoning begin 12-72 hours after eating food, water, or contact with animals contaminated with Salmonella. These include the traditional food poisoning symptoms of abdominal pain, diarrhea, vomiting, and fever. The symptoms generally last two to five days. Dehydration can be a complication in severe cases. People generally recover without antibiotic treatment, although they may feel tired for a week after the active symptoms subside. The CDC estimates that there are over 500 fatalities per year in the US, with 2% of the cases complicated by chronic arthritis.

Staphylococcus aureus

Staphylococcus aureus is found in dust, air, and sewage. The bacteria are spread primarily by food handlers using poor sanitary practices. Almost any food can be contaminated, but salad dressings, milk products, cream pastries, and any food kept at room temperature, rather than hot or cold, are likely candidates.

It is difficult to estimate the number of cases of food poisoning from Staphylococcus aureus that occur each year, because its symptoms are so similar to those caused by other foodborne bacteria. Many cases are mild and the victim never sees a doctor.

Symptoms appear rapidly, usually two to eight hours after the contaminated food is eaten. The acute symptoms of vomiting, diarrhea, and severe abdominal cramps usually last only three to six hours and rarely more than 24 hours. Most people recover without medical assistance. Deaths are rare.

Escherichia coli (E. coli)

There are many strains of E. coli, and not all of them are harmful. The strain that causes most severe food poisoning is E. coli O157:H7. Food poisoning by E. coli occurs in three out of every 10,000 people. Foodborne E. coli is found mainly in food derived from cows such as dairy products and beef, especially ground beef.

Symptoms of food poisoning from E. coli are slower to appear than those caused by some of the other foodborne bacteria. E. coli produces toxins in the large intestine rather than higher up in the digestive system. This factor accounts for the delay in symptoms and the fact that vomiting rarely occurs in E. coli food poisoning.

One to three days after eating contaminated food, the victim with E. coli O157:H7 begins to have severe abdominal cramps and watery diarrhea that usually becomes bloody within 24 hours. There is little or no fever, and rarely does the victim vomit. The bloody, watery diarrhea lasts from one to eight days in uncomplicated cases. E. coli is the most common cause of "travelers' diarrhea," affecting people travelling to many high-risk areas such as Latin America, Asia, Africa, and the Middle East. It is most often caused by water or foods contaminated with fecal matter.

Campylobacter jejuni (C. jejuni)

According to the FDA, C. jejuni is the leading cause of bacterial diarrhea in the United States. It is responsible for more cases of bacterial diarrhea than Shigella and Salmonella combined. Anyone can get food poisoning from C. jejuni, but children under five and young adults between the ages of 15 and 29 are more frequently infected.

C. jejuni is carried by healthy cattle, chickens, birds, and flies. It is not carried by healthy people in the United States or Europe. The bacterium is also found in ponds and stream water. The ingestion of only a few hundred C. jejuni bacteria can make a person sick.

Symptoms of food poisoning begin two to five days after eating food contaminated with C. jejuni. These symptoms include fever, abdominal pain, nausea, headache, muscle pain, and diarrhea. The diarrhea can be watery or sticky and may contain blood. Symptoms last from seven to 10 days, and relapses occur in about one quarter of people who are infected. Dehydration is a common complication. Other complications such as arthritis-like joint pain and hemolytic-uremic syndrome (HUS) are rare.

Shigella

Shigella is a common cause of diarrhea in travelers to developing countries. It is associated with contaminated food and water, crowded living conditions, and poor sanitation. The bacterial toxins affect the small intestine.

Symptoms of food poisoning by Shigella appear 36 to 72 hours after eating contaminated food. These symptoms are slightly different from those associated with most foodborne bacteria. In addition to the familiar watery diarrhea, nausea, vomiting, abdominal cramps, and fever, up to 40% of children with severe infections show neurological symptoms, including seizures caused by fever, confusion, headache, lethargy, and a stiff neck that resembles meningitis.

The disease runs its course in two to three days. Dehydration is a common complication. Most people recover on their own, although they may feel exhausted. Children who are malnourished or have weakened immune systems may die.

Clostridium botulinum (C. botulinum)

C. botulinum, which causes both adult botulism and infant botulism, is unlike any of the other foodborne bacteria. First, C. botulinum is an anaerobic bacterium that can only live in the absence of oxygen. Second, the toxins from C. botulinum are neurotoxins. They poison the nervous system, causing paralysis without the vomiting and diarrhea associated with other foodborne illnesses. Third, toxins that cause adult botulism are released when the bacteria grow in an airless environment outside the body. They can be broken down and made harmless by heat. Finally, botulism is much more likely to be fatal, even in tiny quantities.

Adult botulism outbreaks are usually associated with home canned food, although occasionally commercially canned or vacuum-packed foods are responsible for the disease. C. botulinum grows well in nonacidic, oxygen-free environments. If food is canned at too low heat or for too brief a time, the bacterium is not killed. It reproduces inside the can or jar, releasing its deadly neurotoxin. The toxin can be made harmless by heating the contaminated food to boiling for ten minutes. However, even a very small amount of the C. botulinum toxin can cause serious illness or death.

Symptoms of adult botulism appear about 18 to 36 hours after the contaminated food is eaten, although there are documented times of onset ranging from four hours to eight days. Initially a person suffering from botulism feels weakness and dizziness followed by double vision. Symptoms progress to difficulty speaking and swallowing. Paralysis moves down the body, and when the respiratory muscles are paralyzed, death results from asphyxiation. People who show any signs of botulism poisoning must receive immediate emergency medical care to increase their chance of survival.

Infant botulism is a form of botulism first recognized in 1976. It differs from foodborne botulism in its causes and symptoms. Infant botulism occurs when a child under the age of one year ingests the spores of C. botulinum. These spores are found in soil, but a more common source of spores is honey.

The C. botulinum spores lodge in the baby's intestinal tract and begin to grow, producing their neurotoxin. Onset of symptoms is gradual. Initially the baby is constipated, which is followed by poor feeding, lethargy, weakness, drooling, and a distinctive wailing cry. Eventually the baby loses the ability to control its head muscles. From there the paralysis progresses to the rest of the body.

Rotavirus

The clinical characteristics of rotavirus include vomiting and watery diarrhea for three to eight days with abdominal pain and fever also frequently occurring. The incubation period is about two days. Subsequent bouts of rotavirus tend to be less severe than the initial infection. Illness can occur when in contact with contaminated food, water, or surfaces. Rotavirus infections are higher in countries with temperate climates (November to April in the United States) with most infections occurring in children under two years old. Adult cases tend to be milder.

Bovine spongiform encephalopathy and Creutzfeldt-Jakob disease

It is extremely unlikely that Bovine spongiform encephalopathy will become a foodborne illness in the United States, because the feeding of ruminant byproducts to other animals was probably a factor that lead to the outbreak in the United Kingdom. Furthermore, the FDA implemented a ban on ruminant feed in 1997 due to evidence that BSE can be transmitted to humans.

Creutzfeldt-Jakob disease has atypical clinical symptoms, including psychiatric or sensory symptoms early in its course, and neurological abnormalities and dementia later. Incidence of CJD in people under 30 years is extremely rare in the United States (less than five cases per 1 billion per year). In the United Kingdom, it primarily affects younger people with over half of the patients who have died of CJD under 30 years old.

Diagnosis

One important aspect of diagnosing food poisoning is for doctors to determine if a number of people have eaten the same food and show the same symptoms of illness. When a cluster of cases occurs, food poisoning is strongly suspected. The diagnosis is confirmed when the suspected bacterium is found in a stool culture or a fecal smear from the person. Other laboratory tests are used to isolate bacteria from a sample of the contaminated food. Botulism is usually diagnosed from its distinctive neurological symptoms, since rapid treatment is essential. Many cases of food poisoning go undiagnosed, since a definite diagnosis is not necessary to effectively treat the symptoms. Because it takes time for symptoms to develop, it is not necessarily the most recent food one has eaten that causes the symptoms.

Treatment

Treatment of most food poisoning, except that caused by C. botulinum, focuses on preventing dehydration by replacing fluids and electrolytes lost through vomiting and diarrhea. Electrolytes are salts and minerals that form electrically charged particles (ions) in body fluids. Electrolytes are important because they control body fluid balance and are important for all major body reactions. Pharmacists can recommend effective, pleasant-tasting, electrolytically balanced replacement fluids that are available without a prescription. When more fluids are being lost than can be consumed, dehydration may occur. Dehydration is more likely to happen in the very young, the elderly, and people who are taking diuretics. To prevent dehydration, a doctor may give fluids intravenously.

In very serious cases of food poisoning, medications may be given to stop abdominal cramping and vomiting. Anti-diarrheal medications are not usually given. Stopping the diarrhea keeps the toxins in the body longer and may prolong the infection.

People with food poisoning should modify their diet. During the period of active vomiting and diarrhea, they should not try to eat and should drink only clear liquids frequently but in small quantities. Once active symptoms stop, they should eat bland, soft, easily digested foods for two to three days. Such foods include bananas, rice, applesauce, and toast, all of which are easy to digest. Milk products, spicy food, alcohol, and fresh fruit should be avoided for a few days, although babies should continue to breast-feed. These modifications are often all the treatment that is necessary.

Severe bacterial food poisonings are sometimes treated with antibiotics. Trimethoprim and sulfamethoxazole (Septra, Bactrim), ampicillin (Amcill, Polycill) or ciprofloxacin (Ciloxan, Cipro) are most frequently used.

Botulism is treated in a different way from other bacterial food poisonings. Botulism antitoxin is given to adults but not infants if it can be administered within 72 hours after symptoms are first observed. If given later, it provides no benefit.

Both infants and adults require hospitalization, often in the intensive care unit. If the ability to breathe is impaired, patients are put on a mechanical ventilator to assist their breathing and are fed intravenously until the paralysis passes.

Alternative treatment

Alternative practitioners offer the same advice as traditional practitioners concerning diet modification. In addition, they recommend taking charcoal tablets, Lactobacillus acidophilus, Lactobacillus bulgaricus, and citrus seed extract. An electrolyte replacement fluid can be made at home by adding one teaspoon of salt and four teaspoons of sugar to one quart of water. For food poisoning other than botulism, two homeopathic remedies, either Arsenicum album or Nux vomica, are strongly recommended.

Prognosis

Most cases of food poisoning (except botulism) clear up on their own within one week without medical assistance. The patient may continue to feel tired for a few days after active symptoms stop. So long as the patient does not become dehydrated, there are few complications. Deaths are rare and usually occur in the very young, the very old, and people whose immune systems are already weakened.

Complications of Salmonella food poisoning include arthritis-like symptoms that occur three to four weeks after infection. Although deaths from Salmonella are rare, they do occur, mostly in elderly people in nursing homes.

Adults usually recover without medical intervention, but many children need to be hospitalized as the result of E. coli food poisoning. E. coli toxins may be absorbed into the blood stream where they destroy red blood cells and platelets, which are important in blood clotting. About 5% of victims develop hemolytic-uremic syndrome, which results in sudden kidney failure and makes dialysis necessary. (Dialysis is a medical procedure used to filter the body's waste products when the kidneys have failed.)

Botulism is the deadliest of the bacterial foodborne illnesses. With prompt medical care, the death rate is less than 10%.

KEY TERMS

Diuretic— Medication that increases the urine output of the body.

Electrolytes— Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Lactobacillus acidophilus— This bacterium is found in yogurt and changes the balance of the bacteria in the intestine in a beneficial way.

Platelets— Blood cells that help the blood to clot.

Health care team roles

Definitive identification of food poisoning is made by a physician, usually with the aid of stool or blood cultures. Nurses, medical technologists, and other health care professionals often aid in taking and analyzing cultures, and in educating patients about preventive measures they can take to avoid food poisoning.

Prevention

Food poisoning is almost entirely preventable by practicing good sanitation and good food handling techniques. These include:

• Keep hot foods hot and cold foods cold.
• Cook meat to the recommended internal temperature. Use a meat thermometer to check. Cook eggs until they are no longer runny.
• Refrigerate leftovers promptly. Do not let food stand at room temperature.
• Avoid contaminating surfaces and other foods with the juices of uncooked meats.
• Wash fruits and vegetables before using.
• Purchase pasteurized dairy products and fruit juices.
• 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.

Resources

PERIODICALS

Sanders, TA. "Food Production and Food Safety." British Medical Journal 318 (1999):1689-93.

ORGANIZATIONS

Centers for Disease Control and Prevention. 〈http://www.cdc.gov〉.

United States Department of Agriculture. Food Safety and Inspection Service. Washington, DC 20250. (800) 535-4555. 〈http://www.fsis.usda.gov/〉.

USDA/FDA Foodborne Illness Education Information Center. National Agricultural Library/USDA. Beltsville, MD 20705-2351. (301) 504-5719. Fax (301) 504-6409. foodborne@nal.usda.gov. 〈http://www.nal.usda.gov/foodborne/index.html〉.

OTHER

Agriculture Network Information Center. 〈http://www.agnic.org/〉.

The Food and Nutrition Information Center (FNIC), part of the U.S. Department of Agriculture (USDA) and the Agricultural Research Service (ARS). 〈http://www.nal.usda.gov/fnic/index.html〉.

FoodSafety.gov. U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. 〈http://www.foodsafety.gov〉.

National Food Safety Information Network 〈http://www.foodsafety.gov/∼fsg/network.html〉.

U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. Bad Bug Book. 〈http://vm.cfsan.fda.gov〉.