Staphylococcus (Staph) Aureus
What is Staphylococcus aureus?
Staphylococcus aureus is the most common cause of foodborne illness. Commonly called "staph," this bacterium produces a poison/toxin that causes the illness.
What are the symptoms of "staph?"
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.
What foods could make me sick?
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.
Where do staphylococci come from?
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.
How frequently do people get sick?
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.
What is the treatment for staph?
The objective of treatment is to replace fluids, salt, and minerals that are lost by vomiting or diarrhea.
How can I prevent spreading staph?
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).
A Case in Point ...
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.