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 or certain seafood. Symptoms of food poisoning usually involve nausea, vomiting and/or diarrhea. Some food-borne toxins can affect the nervous system.

Description

Every year millions of people suffer from bouts of vomiting and diarrhea each year that they blame on "something I ate." These people are generally correct. Each year in the United States, one to two bouts of diarrheal illness occur in every adult. 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. 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 or other E. coli strains, 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 (such as the Norwalk agent that causes diarrhea and the viruses of hepatitis A and E), environmental toxins (heavy metals), and poisons produced within the food itself (mushroom poisoning or fish and shellfish poisoning).

Careless food handling during the trip from farm to table creates conditions for the growth of bacteria that make people sick. 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 food-borne bacterial diseases. The United States Food and Drug Administration (FDA) estimates that 60% 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 re-contaminated if it comes in contact with plates, cutting boards, countertops, 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 bacteria Staphylococcus aureus in their nasal passages and throat, and 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 bacteria 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.

— Suzanne M. Lutwick, MPH

1. An acute, often severe gastrointestinal disorder characterized by vomiting and diarrhea and caused by eating food contaminated with bacteria, especially bacteria of the genus Salmonella, or the toxins they produce.
2. Poisoning caused by ingesting substances, such as certain mushrooms, that contain natural toxins.

For more information on food poisoning, visit Britannica.com.

An acute gastrointestinal or neurologic disorder caused by bacteria or their toxic products, by viruses, or by harmful chemicals in foods.

Bacteria may produce food poisoning by three means: (1) they infect the individual following consumption of the contaminated food; (2) they produce a toxin in food before it is consumed; or (3) they produce toxin in the gastrointestinal tract after the individual consumes the contaminated food.

Infectious bacteria associated with food poisoning include Brucella, Campylobacter jejuni, enteroinvasive Escherichia coli, enterohemorrhagic E. coli, Listeria monocytogenes, Salmonella, Shigella, Vibrio parahaemolyticus, V. vulnificus, and Yersinia enterocolitica. These organisms must be ingested for poisoning to occur, and in many instances only a few cells need be consumed to initiate a gastrointestinal infection. Salmonella and C. jejuni are the most prevalent causes of food-borne bacterial infections. See also Yersinia.

Staphylococcus aureus and Clostridium botulinum are bacteria responsible for food poisonings resulting from ingestion of preformed toxin. Staphylococcus aureus produces heat-stable toxins that remain active in foods after cooking. Clostridium botulinum produces one of the most potent toxins known. Botulinal toxin causes neuromuscular paralysis, often resulting in respiratory failure and death. See also Botulism; Staphylococcus; Toxin.

Food-poisoning bacteria that produce toxin in the gastrointestinal tract following their ingestion include Bacillus cereus, Clostridium perfringens, enterotoxigenic E. coli, and V. cholerae. Bacillus cereus and C. perfringens are spore-forming bacteria that often survive cooking and grow to large numbers in improperly refrigerated foods. Following ingestion, their cells release enterotoxins in the intestinal tract. Enterotoxigenic E. coli is a leading cause of travelers' diarrhea. See also Diarrhea; Escherichia.

Viruses that cause food-borne disease generally emanate from the human intestine and contaminate food through mishandling by an infected individual, or by way of water or sewage contaminated with human feces. Hepatitis A virus and Norwalk-like virus are the preeminent viruses associated with food-borne illness. See also Hepatitis.

Chemical-induced food poisoning is generally characterized by a rapid onset of symptoms which include nausea and vomiting. Foods contaminated with high levels of heavy metals, insecticides, or pesticides have caused illness following ingestion. See also Food microbiology; Medical bacteriology; Toxicology.

May be due to (1)contamination with harmful bacteria or other micro-organisms; (2)toxic chemicals; (3) adverse reactions to certain proteins or other natural constituents of foods;(4)chemical contamination. See also food-borne disease.

The commonest bacterial contamination is due to species of Salmonella, Staphylococcus, Campylobacter, Listeria, Bacillus cereus, and Clostridium welchii. Very rarely, food poisoning is due to Clostridium botulinum, see botulism.

Staphylococcal poisoning causes rapid symptoms (within 2-4 hours): abdominal cramp, nausea, vomiting, and diarrhoea; recovery is normally rapid. Salmonellae produce an endotoxin which is not destroyed by cooking and causes acute gastro-enteritis after 12-24 hours: nausea, vomiting, and diarrhoea may persist for several weeks.

A disorder of the digestive system caused by eating food contaminated with bacteria, fungi (such as moulds), viruses, their products, or a non-biological poison. Symptoms vary depending on the type of food poisoning, but usually include nausea, abdominal pain, diarrhoea, and a headache. Some types of bacterial and viral infections can be fatal to the elderly, the young, and those with poor immune systems. Most food poisoning is caused by bacteria, such as the well-known Salmonella and Listeria. Less well known is a group of bacteria called Campylobacter which are transmitted in untreated water, unpasteurized or poorly pasteurized milk, and insufficiently cooked meats. Apparently, in the UK the disease may also be spread by birds pecking at milk bottle tops. Symptoms of food poisoning by Campylobacter range from mild diarrhoea to death. Food poisoning associated with the bacterium Bacillus cereus is also a major problem. The bacterium thrives in cooked rice kept warm but not hot in some take-away restaurants.

Nearly all food contains bacteria, but most are harmless unless they are allowed to multiply quickly. Cooking at high temperature kills most bacteria, and refrigeration retards their growth. However, food left at room temperature for long periods may enable certain bacteria (e.g. Clostridium perfringens) to multiply and produce high levels of toxin which is still effective after heating or freezing. The risk of food poisoning is greatly reduced by proper hygienic handling and preparation of the food. See also botulism; campylobacteriosis; cholera; listeria; parahaemolyticus food poisoning; salmonellosis; shigellosis; staphylococcal 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. jejuniinfections 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]. .

Merck & Co., Inc. "E. coli O157:H7 Infection." The Merck Manual Online. [cited October 2002]. .

Merck & Co., Inc. "Gastroenteritis." The Merck Manual Online. [cited October 2002]. .

[Article by: Patience Paradox; Teresa G. Odle]

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:

• 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).

[Article by: L. Lee Culvert Suzanne M. Lutwick, MPH]

Illnesses that arise from eating food contaminated with pathogenic or toxic (see toxins) substances. Characterized by vomiting and diarrhea, food poisoning is often caused by bacteria, such as salmonella or staphylococci. (See botulism.)