Staphylococcus aureus

Some S. aureus strains are capable of producing a highly heat-stable protein toxin causing Staphylococcal food poisoning.

The onset of symptoms is usually rapid, depending on individual susceptibility to the toxin, the amount of contaminated food eaten, the amount of toxin in the food ingested, and the general health of the victim.

Common symptoms may include nausea, vomiting, retching, abdominal cramping, and prostration.

In severe cases, headache, muscle cramping, and transient changes in blood pressure and pulse rate occur. Recovery takes two days, but may take longer in severe cases.

A toxin dose of less than 1.0 microgram in food will produce symptoms of staphylococcal poisoning.

To diagnosis staphylococcal food borne illness, interviews with the victims and gathering and analysing data is important. Suspect foods should be collected and examined for staphylococci. The presence of relatively large numbers of enterotoxigenic staphylococci is good circumstantial evidence that the food contains toxin. The most conclusive test is the linking of an illness with a specific food or in cases where multiple vehicles exist, the detection of the toxin in the food sample(s). In cases where the food may have been treated to kill the staphylococci, as in pasteurisation or heating, direct microscopic observation of the food may helpful.

Serological tests to determine the enterotoxigenicity of S. aureus isolated from foods as well as methods for the separation and detection of toxins in foods have been used. Phage typing may also be useful when viable staphylococci can be isolated from the incriminated food, from victims, and from suspected carrier such as food handlers.

Foods associated with staphylococcal food poisoning include meat and meat products; poultry and egg products; salads such as egg, tuna, chicken, potato, and macaroni; bakery products such as cream-filled pastries, cream pies, and chocolate éclairs; sandwich fillings; and milk and dairy products. Also foods that require considerable handling during preparation and that are kept at slightly elevated temperatures after preparation.

Staphylococci exist in air, dust, sewage, water, milk, and food or on food equipment, environmental surfaces, humans, and animals. Humans and animals are reservoirs where staphylococci are in the nasal passages and throats and on the hair and skin of 50 percent or more of healthy people. Food handlers are the main source of food contamination in food poisoning outbreaks, but equipment and environmental surfaces are also sources of contamination with S. aureus .

Human intoxication is caused by the enterotoxins produced by some strains of S. aureus , usually because the food has not been kept hot enough (60°C, 140°F, or above) or cold enough (7.2°C, 45°F, or below).

Death from staphylococcal food poisoning is very rare, although such cases have occurred among the elderly, infants, and severely debilitated persons