Staphylococcal food poisoning is the most common bacterial food poisoning observed in the all the world. Foods may produce illness in three ways: They may become contaminated with microorganisms or their products, they may themselves be poisonous, or they may contain noxious chemicals. It is caused by the ingestion of a preformed exotoxin produced in contaminated food. Because it characteristically produces only brief illness, staphylococcal food poisoning often goes unnoticed and is brought to the attention of public health authorities only when it occurs in outbreaks involving large numbers of people. Most people on some occasion are victims of this intoxication.
Etiology and Pathogenesis.
Only certain strains of coagulase-positive Staphylococcus produce the extracellular enterotoxin responsible for food poisoning. Most enterotoxigenic strains belong to phage groups III and IV and particularly to phage types 42D or 6/47. Coagulase-negative strains do not elaborate enterotoxin. The toxin itself is a protein of low molecular weight, and four types, A, B, C, and D, are currently recognized. The toxin is relatively heat-stable and has produced symptoms of food poisoning after exposure to a temperature equivalent to that of boiling water.
Foods are generally contaminated with enterotoxigenic strains of staphylococci from the hands of workers preparing them. Often the responsible individual has only a minor skin infection or is simply found to be a nasal carrier of an enterotoxigenic strain. Occasionally, a cow or goat with mastitis is the source of contaminated milk. In the United States’, custard or cream-filled bakery goods are the foods most commonly responsible for staphylococcal food poisoning. Ham, tongue, and other processed meats, cheese, ice cream, potato salad, hollandaise sauce, chicken salad, and human and goat’s milk are foods often implicated. Foods containing enterotoxin have normal appearance, odor, and taste.Enterotoxin has been produced by viable staphylococci in contaminated foods after only four to five hours’ incubation at a temperature of 86° F., but it is not formed at refrigerator temperatures (38° to 42° F.).
Here Is Complete Guide About Food Poisoning And Staphylococcal Food Poisoning
Symptoms characteristically appear one to six hours after the ingestion of the contaminated food. The illness may have a sudden onset, with severe, cramping abdominal pain, nausea; retching, vomiting, and diarrhea. Sweating, increased salivation, and headache are sometimes seen. Fever is not a common feature. In some cases prostration may be severe, and shock may occur. However, recovery is generally rapid, symptoms usually disappearing within six to eight hours and rarely lasting longer than 24 hours. Both the incubation period and the severity of symptoms may be influenced by the amount of enterotoxin ingested, but individuals vary considerably in susceptibility to staphylococcal enterotoxin.
Diagnosis. The short incubation period and the presence of similar illness in others who have eaten the same food usually make the clinical diagnosis of staphylococcal food poisoning relatively straightforward. It must be differentiated from other bacterial food poisonings, and an isolated case must be differentiated from acute cholecystitis, appendicitis, and other intra abdominal surgical emergencies. The rapid onset and absence of high fever are helpful clues. The neurologic symptoms noted with botulism help differentiate it from staphylococcal food poisoning. Poisonings caused by other foods and chemical agents usually cause symptoms within an hour and are often accompanied by neurologic signs that are absent in staphylococcal food poisoning.
By taking a careful food history it is often possible to decide which food was implicated in the poisoning. If possible, portions of it should be obtained for bacteriological examination. Gram stains and cultures should be performed. Cultures may yield few staphylococci because the food may have been heated sufficiently to kill the microorganisms but not to destroy the enterotoxin. In such cases the Gram stain may still show clumps of gram-positive cocci. Definitive diagnosis rests on the demonstration of enterotoxin in the suspected food or the production of enterotoxin by strains isolated from the food. This has proved to be a difficult task, for most laboratory animals are quite insensitive to enterotoxin; the most reliable test must be performed on either human volunteers or monkeys. Recently, immunological assays utilizing gel diffusion techniques have shown promise for demonstrating enterotoxin in contaminated foods.
Treatment arid Prognosis. In most cases no specific treatment is needed. Occasionally, a patient with severe vomiting and diarrhea becomes dangerously dehydrated and requires intravenous replacement of fluids containing sodium chloride and potassium. Antimicrobial therapy is not indicated.Elderly, debilitated persons or young infants may die; otherwise, the prognosis is excellent.
Prevention measures must be directed against heavy contamination of foods with Staphylococcus. Food handlers should be trained to observe strict personal hygiene and should be forbidden to work when they have active staphylococcal lesions. Because enterotoxin is not produced at temperatures below 42.8° F. (6° C.), the best preventive measure is careful refrigeration of all perishable foods. Foods should be reheated immediately before serving and should not be allowed to stand for long periods at room temperature.