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AACC International Approved Methods - AACC Method 42-30.03. Enumeration of Staphylococcus aureus

AACC International Approved Methods

Microorganisms

AACCI Method 42-30.03
Enumeration of Staphylococcus aureus

VIEW METHOD

Objective
Staphylococcus aureus is a microorganism that can produce a heat-stable enterotoxin. Consumption of foods containing staphylcoccal enterotoxin has resulted in illness. The enumeration of S. aureus is important, but results need to be interpreted carefully. In most cases, large numbers of the pathogen must be present to produce enough enterotoxin to elicit a clinical response. Foods containing large numbers of S. aureus are not necessarily unsafe. It is therefore important to determine whether the isolated strain is enterotoxigenic or possesses markers that are linked to toxigenic strains (i.e., coagulase). Additionally, it is essential that the history of the suspect food be determined. Temperature abuse of foods, particularly those containing a protein source, and how the product was processed and handled must be reviewed. Understanding how the food was processed is important, since heating may destroy S. aureus cells but does not inactivate the heat-stable enterotoxin. In such a case, the levels of S. aureus would be low or not present, but the food would pose a health hazard if consumed. This has been shown with foods such as dried pasta and canned mushrooms. Coagulase-positive staph are also commonly used when developing microbiological specifications for foods and food ingredients. They can be a concern if that food or food ingredient contains protein or is destined for use in protein-containing foods. The method is applicable to all raw and processed foods and ingredients.