The term food poisoning in its wider sense includes all illnesses which result from ingestion of food containing non-bacterial or bacterial products. But the term is usually restricted to acute gastroenteritis due to the bacterial infection of food or drink.
Causes:
(I) Poisoning due to bacteria and toxins.
(II) Poisons of vegetable origin (natural food poisons):
(1) Lathyrus sativus.
(2) Poisonous mushrooms.
(3) Rye, oats, barley, etc.
(4) Poisonous berries, such as atropa belladonna.
(5) Lolium temulentum.
(6) Paspalam scrobiculatum.
(7) Argemone mexicana.
(8) Cotton seeds.
(9) Ground nuts.
(10) Vitia fava.
(11) Cabbage.
(12) Solanine.
(13) Soya bean.
(14) Sweet clover.
(III) Poisons of animal origin:
(1) Poisonous fish.
(2) Mussel.
(IV) Chemical:
(1) Intentionally added, such as flavoring agents in processed food, coloring agents, preservatives, extraction of fat by solvents like hydrocarbons.
(2) Accidentally added, such as pesticides and insecticides.
(3) Products of food processing, e.g. Smoking of fleshy foods.
(4) Radionucleides.
BACTERIAL FOOD POISONING:
Bacterial food poisoning is divided into two groups:
(1) -the infection type, which follows the multiplication within the body of pathogenic organisms contained in the food.
(2) the toxin type, which follows the ingestion of food in which poisonous substances have been formed due to bacterial proliferation. In the infection type the organisms belong mainly to the salmonella group, e.g. S. enteritidis of Gaertner, S. typhimurium, S.cholerasuis, and less commonly the paratyphoid bacilli. Salmonella invade and destroy mucosa of small intestine. Watery diarrhea stained with blood or mucus occurs in 12 nours to two days. Other organisms like Proteus, Coli. group, Streptococci, Sh.flexneri, and Sh. sonnei are also involved, and also certain poisonous food, such as fish, toadstools, eggs, ergot, etc. Vibrio parahaemolyticus contained in sea food invades intestinal mucosa and produces watery diarrhea and vomiting in 6 hours to four days.
Bacterial food poisoning results from the ingestion of contaminated food, uncooked food or imperfectly cooked food. Diarrhea in several patients after twenty-four to forty-eight hours of eating the same meal indicates ingestion of the salmonella.
The toxic type is due to ingestion of preformed toxin in prepared food, such as canned or preserved food. Exotoxins, e.g. enterotoxin of staphylococci and the botulinum toxin, produce intoxication. Bacillus cereus also produces enterotoxins. The materials usually affected are meat, milk, fish or egg. Less frequently, vegetables and cereals, and very rarely fruits are affected. Cheese, meat, fish, sandwiches, and other canned and preserved meats and imperfectly cooked and uncooked food often serve as vehicles. The food may not be altered in look, smell or taste. Meat and other food materials may be infected due to disease in the animal, e.g., sick cattle or pigs.
Enterotoxin, which resists boiling for thirty minutes and the action of intestinal enzymes, is an important cause of food poisoning. Symptoms such as diarrhea, nausea, abdominal cramps, and vomiting occur for a short time and the patient recovers as soon as the enterotoxins have been neutralized and metabolized, usually within twenty-four hours of poisoning. Extraneous infection may occur by a human carrier transmitting it during slaughtering of animals or during preparation of the food. Rats and mice harboring infection may contaminate the food by their excreta before or after preparation.
Food poisoning is common in summer, because the warm temperature favors multiplication of microorganisms. It may occur as isolated cases or small outbreaks. The main diseases spread by infected food are:
(1) The enteric group.
(2) Cholera.
(3) Bacillary dysentery.
(4) Staphylococcal and other bacterial infections.
(5) Amoebic dysentery and other protozoal infections.
(6) Acute infective hepatitis.
(7) Brucellosis.
(8) Various worm infestations.
(9) Schistosomiasis.
(10) Traveler’s diarrhea (due to pathogenic E.coli). E. Coli invade intestinal mucosa and elaborate enterotoxin. Infection occurs through water and meat. Incubation period is 1 to 3 days. Symptoms resemble dysentery or cholera.
At autopsy, the mucosa of the stomach and intestines is swollen and often intensely congested and there may be minute ulcers. Microscopic examination shows fatty degeneration of the liver. The causative organism can be isolated from the blood and viscera.
In the toxin type, the incubation period is one to six hours. The symptoms resemble those of infection type but vomiting tends to be more violent, diarrhea is less, prostration is greater, fever may be absent and recovery more rapid, often within twenty-four hours. The mortality is very low, being about one percent.
Diagnosis:
This is made from: (1) History. (2) Clinical features. (3) Isolation of the organism from the remnants of suspected food and from vomit, faeces, blood, etc. from sick person. (4) The injection of portion of left off food into mice or guinea pigs should be performed. If the animals get sick, attempt should be made to isolate organisms from them.
Treatment and Prophylaxis:
Wash-out the stomach and give purgatives. Glucose-saline infusion should be given to promote elimination of the toxins from the system. Meat inspection at the slaughter house is very important. The rodents should be driven out from places where food industry is carried on. Carriers should not be employed in dairies and in food industry. Preserved foods and dried egg powder should be properly cooked.
Botulism:
This form of food poisoning differs from the other two types, in that there are no symptoms of gastroenteritis, although poisoning results from absorption of a specific toxin from the alimentary canal. Cl. botulinum does not grow in body, but produces a potent neurotoxin. It is normally present in the soil and by soil contamination, food may become infected, especially fruits and vegetables. Eight distinct strains (type A to G) of Cl. botulinum have been identified. Food contaminated by types A and B often appear putrefied due to the action of proteolytic enzymes.
Food contaminated with type E toxin may look and taste normal. The toxin inhibits acetylcholine. The toxin is destroyed by heat at 80°C for 30 min. or 100°C for 10 min.
Botulism is intoxication, not an infection. The causative organism Cl. botulinum multiplies in the food, e.g., sausages, tinned meat, fish, fruits, etc. before it is consumed, and produces a powerful exotoxin. The fatal dose for an adult is 0.01 mg. or even less. The toxin paralyses the nerve endings, by blocking the nerve impulses at the myoneural junctions. It blocks the action of acetylcholine. Its action is selective being confined to the cholinergic fibers of the autonomic nervous system.
Signs and Symptoms:
The incubation period varies from twelve to thirty hours, but may be prolonged to seventy-two hours. Symptoms are mainly due to the action of the toxin on the central nervous system. The initial Gl symptoms include nausea, vomiting, abdominal distension and pain.
Later symptoms are: dry-or sore mouth or throat. difficulty with visual accommodation, dysphonia, diplopia, descending bilaterally symmetrical motor paralysis initiated by abducent or oculomotor nerve palsy, dysphagia, constipation, respiratory insufficiency, and urinary retention. The patient is conscious until death, which is preceded by coma or delirium.
The temperature is usually subnormal. Death may occur within twenty-four hours from the onset of symptoms, but may be delayed for a week. In those who survive, complete recovery of ocular movements may not take place for six to eight months. Mortality varies from twenty-five to hundred percent. At autopsy, the kidneys, liver and meninges are congested. Histological examination of the organs may show thrombosis.
Diagnosis: This is made from: (1) History. (2) Clinical features. (3) Demonstration of the toxin in the suspected food. (4) Isolation of the bacillus, from the food. (5) Isolation of the toxin in the blood and tissues. (6) Isolation of the bacillus from the patient's faeces or vomit, intestinal contents and viscera.
Treatment: (1) Gastric lavage or emesis. (2) Activated charcoal. (3) Cathartic. (4) Whole bowel irrigation. (5) 50 ml. or more of polyvalent antitoxin serum is given i.v. daily, till the patient recovers. (6) Guanidine 15 to 30 mg/kg/day. (7) Adequate respiration. (8) Alcohol precipitates toxin; frequent small doses of brandy are beneficial.
Food Allergy:
It is not food poisoning, for in this the abnormality is not in the food but. in the allergic person. Some persons are hypersensitive to certain types of protein, e.g., meat, fish, eggs, milk, etc. which are ordinarily quite harmless and suffer from gastroenteritis, local urticarial rashes, or asthmatic attack.
Ptomaines:
These are alkaloidal bodies which are formed as the result of bacterial decomposition of protein. When they are formed in the dead tissues, they are known as cadaveric alkaloids. Alkaloids secreted by living cells during metabolism are called leucomaines, which are .slightly toxic when injected into an animal but have no action when ingested.
They are not bacterial poisons and are not derived from bacteria. They are found only when the food becomes too disagreeable to be eaten. Most of the ptomaines are non-poisonous except neurine and mydalein, which are produced in traces five to seven days after death. The symptoms resemble that of atropine. Ptomaines are not the causative agents of food poisoning.
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