Food poisoning may be classified as follows: (a) Chemical food poisoning.
(b) Food poisoning from plants and animals. In relation to this accidental or deliberate ingestion of poisonous substances that have been mixed with articles of food or drink are not discussed. (c) Food poisoning by bacteria and their toxins.
(a) Chemical Food Poisoning:
It usually occurs by the use of cheap enamel wares which may contain antimony and if the enamel comes in contact with acidic foods it may dissolve antimony and cause poisoning. Other chemicals which may cause food poisoning include arsenic, cadmium, cyanide, copper sulphate and flourides. Fertilizers, pesticides and adulterants used in agriculture may be another major source of food poisoning.
(b) Food Poisoning from Plants and Animals:
Ingestion of certain varieties of poisonous mushrooms may cause food poisoning. Similarly ingestion of certain kinds of fish (Shellfish), meat of infected animals or stale meat may cause food poisoning.
(c) Food Poisoning by Bacteria and their Toxins:
Food poisoning by bacteria and their toxins is the commonest cause of food poisoning which is generally caused by ingestion of food and drinks contaminated with bacteria or their products. The bacterial food poisoning is of following types: (i) Salmonella food poisoning (ii) Staphylococcal food poisoning (iii) Botulism (i) Salmonella Food Poisoning: Salmonella food poisoning is caused by salmonella group of microorganisms out of which Sal. typhimurium and Sal. enteritidis are the commonest which cause the poisoning.
The poison is produced within the body of the bacteria. They are non-sporing and are destroyed by heat but the endotoxins are not killed by heat and can withstand a temperature of I00°C. Foods like milk, milk products, egg, egg products, meat, fish and stored food get contaminated with these bacteria and when ingested, the micro-organisms multiply in the intestine and cause illness in about 12 to 24 hours. The prominent symptoms include acute gastro-intestinal irritation i.e. nausea, vomiting, diarrhoea, pain in the abdomen weight loss, severe dehydration and sometimes death of the patient. (ii) Staphylococcal Food Poisoning: It is the most common cause of food poisoning.
The enterotoxins are produced by staphylococci in foods as a result of the multiplication of bacteria before ingestion. The toxin produced by the bacteria is termed as enterotoxin because of its ability to cause gastroenteritis or inflammation of the lining of the intestinal tract. The organism involved is S.
aureus which produces a heat-stable enterotoxin. Due to its heat resistant nature, the toxin cannot be inactivated during normal cooking, and thus causes food poisoning. Staphylococcal food poisoning spreads from ice-creams, milk, milk products, pastries, cakes and when meat in taken in an uncooked or partially cooked form. The symptoms of food poisoning usually appear 2 to 4 hours after the ingestion of contaminated food which include nausea, vomiting, headache, sweating, and abdominal cramps. In severe cases there is blood and mucous in stools, muscular cramps, a weak pulse and shallow respiration. There may be dehydration due to which patient may die. In severe dysentery and vomiting, a saline solution should be administered intravenously to restore the body fluids and the electrolyte balance. (iii) Botulism: It is a fatal form of food poisoning which is caused by the ingestion of food contaminated with neurotoxins produced by Clostridium botulinum which is found in under-processed, tinned (preserved) foods, preserved pickles, fruits and vegetables etc.
The toxin in produced in preserved foods containing proteins and never in fresh foods. The optimum temperature for the growth of these bacteria and for the production of toxin is considered to be 37°C. The botulinum toxin is thermolabile whereas spores of Clostridium botulinum can withstand storage conditions and remain present in pre-cooked frozen foods.
The modern food processing techniques are designed in such a way as to eliminate the heat resistant botulinum spores in food and thus the disease is no longer common now. The symptoms of botulism appear within 12-20 hours after the j consumption of food. The symptoms include nausea, vomiting, diarrhoea headache, dryness of mouth, double vision and decreased salivary secretions.
Death may occur in 4-6 days due to heart failure or respiratory failure. The incidence of bacterial food poisoning is the highest in summer and rainy months due to high temperature and moisture content present in the atmosphere which are quite favourable for bacterial growth.