S. aureus is found on the skin and in the nostrils of many healthy individuals. These bacteria often give rise to minor superficial diseases, including the formation of pustules or boils in hair follicles. S. aureus infections are characterized by the presence of pus and formation of abscesses. In addition to skin pustules, boils, and carbuncles, S. aureus is responsible for impetigo, infections of wounds and burns (particularly in a hospital environment), breast abscesses, whitlow (inflammation of a finger or toe near the nail), osteomyelitis, bronchopneumonia, septicemia, acute endocarditis, food poisoning, and scalded skin syndrome. Scalded skin syndrome occurs in newborns and is due to infection by toxigenic strains of S. aureus. The toxins cause the skin to exfoliate, which leaves an appearance of having been scalded.

S. epidermis does not usually cause infection, occurring universally in a harmless symbiotic relationship. It is usually present on most areas of the skin, in the nostrils, mouth, external ear, and urethra. However, S. epidermis can take advantage of a host with a suppressed immune system and can aggravate an existing condition. Following heart surgery, S. epidermis may cause endocarditis. S. epidermis may turn an existing abnormality in the urinary tract into cystitis.

What disease does Staphylococcus cause?

Staphylococcal food poisoning (staphyloenterotoxicosis; staphyloenterotoxemia) is the name of the condition caused by the enterotoxins which some strains of S. aureus produce.

What are the symptoms?

The onset of symptoms in staphylococcal food poisoning is usually rapid and in many cases acute, 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. The most common symptoms are nausea, vomiting, retching, 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 transient changes in blood pressure and pulse rate may occur. Recovery generally takes two days, However, it us not unusual for complete recovery to take three days and sometimes longer in severe cases.Infective dose--a toxin dose of less than 1.0 microgram in contaminated food will produce symptoms of staphylococcal intoxication. This toxin level is reached when S. aureus populations exceed 100000 per gram.

How is it diagnosed?

In the diagnosis of staphylococcal foodborne illness, proper interviews with the victims and gathering and analyzing epidemiologic data are essential. Incriminated 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 pasteurization or heating, direct microscopic observation of the food may be an aid in the diagnosis. A number of serological methods for determining the enterotoxigenicity of S. aureus isolated from foods as well as methods for the separation and detection of toxins in foods have been developed and used successfully to aid in the diagnosis of the illness. 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.

Where is it found?

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