food

Bacterial Food Poisoning.

Bacterial food poisoning may be from any of a number of different microorganisms, and includes (among other types) botulism, campylobacteriosis, Escherichia coli infection, salmonellosis, and shigellosis.

Campylobacteriosis (Campylobacter infection) is the most common foodborne illness. Contaminated or undercooked poultry or meat, unpasteurized (raw) milk, and contaminated water may cause the disease, even though this organism is commonly found in the intestinal tracts of humans and other animals without causing symptoms of illness. Symptoms of campylobacteriosis usually occur within two to ten days of ingesting the bacteria and include mild to severe diarrhea, fever, nausea, vomiting, and abdominal pain. Children, the elderly, and immunocompromised persons are particularly at risk. The bacteria is now recognized as a major contributing factor in the development of guillain-barré syndrome.

Salmonellosis (poisoning with Salmonella) is the second most common type of food poisoning. The source is usually a poultry product. Salmonella species can produce three types of illnesses: typhoid fever, gastroenteritis, and septicemia. The onset of gastroenteritis is usually 12 to 24 hours after ingestion of the contaminated food, with recovery taking from a few days to months, depending on the severity of the incident. The pathologic activity appears to be directly related to local bacterial action within the intestinal lumen and wall rather than from a toxin.

Escherichia coli O157:H7 is one of many strains of E. coli; although most strains are harmless and live in the intestines of humans and other animals, this strain produces a powerful toxin and can cause severe illness. It is most frequently associated with ingestion of undercooked ground beef. Other sources of infection include contaminated sprouts, lettuce, salami, unpasteurized (raw) milk, and juice. Swimming in or drinking water contaminated with sewage can also cause infection. The most common symptoms are abdominal cramps and bloody diarrhea. It is also possible to experience nonbloody diarrhea or no symptoms. Usually there is little or no fever, and the illness may resolve in five to ten days. hemolytic uremic syndrome occurs in 2 to 7 per cent of patients.

Norwalk virus is another cause of food poisoning, usually associated with gastroenteritis. Symptoms are often mild, consisting of nausea, vomiting, diarrhea, and abdominal pain. Headache and low-grade fever may occur. The fecal-oral route via contaminated water or food is the usual method of transmission. Shellfish and salad ingredients are the foods most often implicated. Norwalk viruses are responsible for about one third of the cases of viral gastroenteritis in persons over the age of two years.

Other Poisonous Plants, Berries, and Shellfish. There are a number of poisonous berries and over 80 kinds of poisonous mushrooms. Children are frequently tempted by poisonous holly berries or the berries that grow on privet (the shrub often used for hedges). Adults often place their faith in misinformation about differences between poisonous and edible mushrooms. Although it is possible to learn to identify poisonous mushrooms and berries, it is much wiser to play safe. Children should be taught not to eat things they find in the woods or fields.

Mushroom poisoning can produce seizures, severe abdominal pain, intense thirst, nausea, vomiting, diarrhea, dimness of vision, and symptoms resembling those of alcoholic intoxication. Symptoms appear six to 15 hours after eating. Later, because of toxic injury to the liver and kidney, the person exhibits signs of hepatic and renal failure.

Mussels and clams may grow in beds contaminated by the typhoid bacillus (Salmonella typhi) or other pathogens. In addition, mussels, clams, and certain other shellfish are dangerous during warm seasons of the year, particularly in the Pacific Ocean; they become poisonous as a result of feeding on microorganisms that appear in the ocean in warm weather. Paralytic shellfish poisoning is a condition characterized by paralysis of the respiratory tract. The symptoms vary; there may be trembling about the lips or loss of power in the muscles of the neck. Symptoms develop quickly, within five to 30 minutes after eating.

Botulism is the most dangerous, but fortunately the rarest, type of food poisoning. Botulism-causing Clostridium botulinum bacteria and their spores are often present in the environment. The spores can be found on the surfaces of fruits and vegetables, as well as in seafood. Home-canned, low-acidic foods were once a common source for this type of poisoning. The bacteria and spores themselves are harmless; the dangerous substance is the botulinum toxin produced by the bacteria when they grow. Botulism results in a descending pattern of weakness and paralysis. When it is suspected, serum, feces, and any remaining food should be tested for botulinum toxin; food and fecal samples can also be cultured for Clostridium botulinum. In infant botulism, the toxin is produced when C. botulinum spores germinate in the intestines. Most cases in infants are caused by inhalation of airborne spores, but infants under one year old should not be given honey, which can contain C. botulinum spores.

Treatment. For most bacterial food poisoning, treatment is largely supportive and consists of rest, nothing by mouth until vomiting stops, medication for the diarrhea, and intravenous replacement of fluids and electrolytes as needed. While most bacterial poisonings are self-limiting, botulism must be treated promptly with antitoxin and respiratory support; the greatest threat to life is respiratory failure. A large proportion of persons with botulism whose cases are misdiagnosed or treated improperly have a fatal outcome.

In general, antibiotics are not effective in treating bacterial food poisoning. However, care will be individualized to the patient dependent upon the organism causing the infection and the condition of the patient. Prevention of food poisoning by proper handwashing techniques and appropriate food handling should be emphasized.

In the United States, the Center for Food Safety and Applied Nutrition of the Food and Drug Administration has published the Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, a valuable source for basic facts on this subject.