Update on Food Poisoning (S. aureus)
It’s summertime and that means picnics, barbeques and food potentially left out to spoil. Know how to protect yourself and your loved ones, so you can have a carefree and healthy fun summer.
Staphylococcus aureus is one of the oldest recognized sources of foodborne illness, and is the cause of what was once called “ptomaine poisoning.”
Foods that are frequently incriminated in 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 eclairs; sandwich fillings; and milk and dairy products. Foods that require considerable handling during preparation and that are kept at slightly elevated temperatures after preparation are frequently involved in staphylococcal food poisoning.
Staphylococci exist in air, dust, sewage, water, milk, and food or on food equipment, environmental surfaces, humans, and animals. Humans and animals are the primary reservoirs. Staphylococci are present in the nasal passages and throats and on the hair and skin of 50 percent or more of healthy individuals. This incidence is even higher for those who associate with or who come in contact with sick individuals and hospital environments.
Although food handlers are usually the main source of food contamination in food poisoning outbreaks, equipment and environmental surfaces can also be sources of contamination with S. aureus. Human intoxication is caused by ingesting enterotoxins produced in food 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).
Staphylococcus aureus food poisoning has been studied since 1894. In 1914, an investigator deliberately drank milk that had been contaminated with a culture of the microbe in order to confirm its effect. Staphylococcus aureus enterotoxin first was detected in food in 1930.
What is Staphylococcus aureus, and where is its natural habitat?
Staphylococcus aureus is a gram-positive spherical bacterium (coccus) that grows in grape-like clusters. It is a common inhabitant of the skin, the nostrils, and around the perineal area of humans and many domesticated animals.
How is Staphylococcus aureus transmitted? What is the incubation period of the illness?
Staphylococcus aureus produces a heat-stable toxin (enterotoxin) when given the opportunity to grow under certain conditions of moisture, temperature, pH, and oxygen levels. When a person eats food containing enterotoxin, he or she will develop symptoms within 1-6 hours, depending on the amount of toxin present and the susceptibility of the victim.
What are the symptoms of Staphylococcus aureus food poisoning?
Food poisoning symptoms caused by staphylococcal enterotoxin develop suddenly and typically consist of nausea, vomiting and stomach cramps. Diarrhea and fever can also occur, but are less common.
What is the prognosis of Staphylococcus aureus food poisoning?
Symptoms of staphylococcal food poisoning typically are self-limiting and last 24-48 hours.
What foods carry Staphylococcus aureus?
Many foods of animal origin, including dairy products, may contain low numbers of Staphylococcus aureus; however, this microbe is more often introduced into food by human carriers through lapses in hygiene. If a contaminated food is held at improper temperature, Staphylococcus aureus will multiply and may produce sufficient enterotoxin to cause symptoms.
How can people protect themselves from Staphylococcus aureus?
First, by paying attention to food recall announcements and immediately discarding any recalled food or returning it to the store. Secondly, by not allowing any food to stand for extended periods of time at room temperature. Food that is not to be eaten immediately should be refrigerated or frozen promptly. A frozen, cooked food should be thawed in the refrigerator, and not at room temperature.