Nancy Stehulak
Staphylococcus aureus is the most common cause of foodborne illness. Commonly called "staph," this bacterium produces a poison/toxin that causes the illness.
Symptoms of staphylococcal food poisoning are usually rapid and in many cases serious, depending on individual response to the toxin, the amount of contaminated food eaten, the amount of toxin in the food ingested, and the general health of the victim. The most common symptoms are nausea, vomiting, abdominal cramping, and prostration. Some individuals may not always demonstrate all the symptoms associated with the illness. In more severe cases, headache, muscle cramping, and changes in blood pressure and pulse rate may occur. Recovery generally takes two days. It is not unusual for complete recovery to take three days and sometimes longer.
Foods that are frequently a problem 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 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.
Staph may also be present in raw milk and raw milk products. Staph can cause mastitis in dairy cows, and other infections in meat animals. In this way, such meat sources may cause staph outbreaks in people.
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 methods of transport. 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 staph. People can contract the illness by eating food that is contaminated with any one of many strains of staph, usually because the food has not been kept hot enough or cold enough. Staph bacteria grow and reproduce at temperatures from 50 degrees F to 120 degrees F, with the most rapid growth occurring near body temperature (about 98 degrees F).
The toxin produced by staph bacteria is very heat-stable - it is not easily destroyed by heat at normal cooking temperatures. The bacteria themselves may be killed, but the toxin remains. Careful handling of food that is prepared ahead is important. This is especially important of foods left over after one meal and planned to be used again at a later meal. Quick cooling and refrigeration, or holding at or above 140 degrees F, can help ensure that toxin has no chance to be formed.
It is hard to determine how often staph food poisoning has occurred because many persons do not report it or it is confused with flu symptoms. Death from staphylococcal food poisoning is rare, although such cases have occurred among the elderly, in infants, and ill persons.
The objective of treatment is to replace fluids, salt, and minerals that are lost by vomiting or diarrhea.
Wash hands thoroughly before and after all food preparation. Any food service worker who has skin infections should not be handling food. Food preparation equipment must be thoroughly washed before it is used. Refrigerate meats and leftovers promptly. Keep hot foods hot (over 140 degrees F) and cold foods cold (below 40 degrees F).
1. Christian, Janet and Greger, Janet, Nutrition for Living. Benjamin/Cummings Publishing Company, Fourth Edition, 1994.
2. U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, The Bad Bug Book.
For more information on foodborne illness, contact your local county Extension Agent. See also the additional fact sheets on other foodborne illness.
Recently, 1,364 children became ill out of a total of 5,824 who had eaten lunch served at 16 elementary schools in Texas. The lunches were prepared in a central kitchen and transported to the schools by truck. Studies revealed that 95% of the children who became ill had eaten a chicken salad. The afternoon of the day preceding the lunch, frozen chickens were boiled for three hours. After cooking, the chickens were deboned, cooled to room temperature with a fan, ground into small pieces, placed into 12-inch deep aluminum pans and stored overnight in a walk-in refrigerator at 42 to 45 degrees F.
The following morning, the remaining ingredients of the salad were added and the mixture was blended with an electric mixer. The food was placed in thermal containers and transported to the various schools at 9:30 AM to 10:30 AM, where it was kept at room temperature until served between 11:30 AM and noon. Upon examination of the chicken salad, large numbers of S. aureus were found.
Contamination of the chicken probably occurred when it was deboned. The chicken was not cooled rapidly enough because it was stored in 12-inch deep layers. Growth of the staphylococcus probably occurred also during the period when the food was kept in the warm classrooms. Prevention of this incident would have entailed screening the individuals who deboned the chicken for carriers of staphylococcus, more rapid cooling of the chicken, and adequate refrigeration of the salad from the time of preparation until it was eaten.
Source: U.S. Food and Drug Administration, The Bad Bug Book, Staphylococcus aureus from the World Wide Web.
This material is based on work supported by the Extension Service, U.S. Department of Agriculture, under special project number 96-EFSF-0-3500.
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