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Staphylocococcus aureus (food poisoning)

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Staphylococcal food poisoning is an acute intoxication that occurs when food contaminated with enterotoxin produced by this bacterium is consumed. Although precise data regarding the exact number of cases is lacking, staphylococcal food poisoning is considered to be among the most common causes of gastroenteritis worldwide. The presence of staphylococcal enterotoxin in food is usually due to cross contamination of ready to eat food with either raw food or, most likely, contamination from a food handler that is carrying Staphylococcus aureus. To prevent food becoming contaminated, good food safety practices should be followed, such as practicing frequent hand washing, wearing gloves when handling foods, and ensuring separation between the areas where raw and cooked products are handled.

Illness caused by Staphylococcus aureus is an acute intoxication that develops after the ingestion of food contaminated with the enterotoxin produced by this bacterium. S. aureus is also associated to other health problems ranging from skin infections to severe invasive infections of the lungs or the heart. Drug resistant strains are common, especially in hospital settings. This summary refers solely to staphylococcal food poisoning.

 

Symptoms include:

  • vomiting
  • nausea
  • diarrhea, usually watery but sometimes with blood
  • cramps
  • other symptoms may include mild fever, weakness, dizziness and chills.

Symptoms usually start 1 to 10 hours after exposure and go away in 1 to 2 days. In some cases, the illness may be more severe. If you have serious symptoms, you should see your doctor. 

 

For staphylococcal food poisoning to occur following the ingestion of a given food, two conditions are necessary. First, S. aureus has to be present in the food; second, foods stored at incorrect temperatures and time allow growth of this pathogen and the production of enterotoxin.


Although S. aureus can be found in food-producing animals and raw foods, humans are considered the main reservoir for this pathogen. S. aureus can be present in healthy individuals, usually on the skin and mucous membranes, for example in the nasal cavity. Food can become contaminated during preparation if the food handler is a carrier of S.aureus and this is transferred to the food through direct contact with contaminated skin or by coughing and sneezing.


The growth of S. aureus in food to a sufficient level as to allow enterotoxin production is possible only under certain conditions. For example, it needs temperatures of between 7°C and 48°C to be able to grow, with an optimum temperature of 37°C. Enterotoxin production will only take place once the levels of this microorganism are large (greater than 10,000 S. aureus per gram of food).


The foods that have been most frequently implicated in cases of staphylococcal food poisoning are poultry and cooked meat products such as ham or corned beef. Other foods implicated were milk and milk products, canned food and bakery products.

 

Staphylococcal food poisoning is usually self-limiting, resolving within one or two days. In a small percentage of cases it can be more severe, especially in infants, the elderly and immunocompromised patients.

 

Staphylococcal food poisoning can be confirmed if the enterotoxin or large numbers of S. aureus are found in the food. S. aureus can also be detected in stool samples from patients.   

 

Most people recover without treatment. The administration of fluids is recommended if the diarrhoea or vomiting is severe. Antibiotics are not indicated as the symptoms are caused by the enterotoxin and not the bacteria.

 

Control measures should be applied first to avoid contaminating the food with S. aureus and also to prevent growth and the formation of enterotoxin in the food.


To avoid contaminating the food with S. aureus, handle and prepare food safely:

  • Ensure raw foods of animal origin are obtained following good hygienic practices, to reduce the possibility of S. aureus contamination.
  • Food handlers should use appropriate protective clothing (e.g. gloves) and thoroughly wash hands.
  • Food handlers with skin lesions should have them properly covered prior to handling food. If this is not possible, they should not work while handling food until the lesions have healed.
  • Avoid cross-contamination by keeping work surfaces clean and ensuring separation between areas where raw and cooked foods are manipulated.

To prevent growth of S. aureus and the formation of enterotoxin:

  • Ensure food is maintained either at a temperature above 60°C or refrigerated below 4°C.
  • Cool cooked foods that will not be immediately consumed to below 4°C within 6 hours.
  • When reheating food, ensure that the temperature reaches at least 74°C.
 

SOURCE: Staphylocococcus aureus (food poisoning) ( )
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