December 17, 2009

ARS develops new test for Staph toxin

Researchers from the USDA Agricultural Research Service (ARS) have developed a new rapid method for the testing of staphylococcal enterotoxin A in chicken, beef and dairy products.

Most people need about two days to recover from being sickened by foods contaminated with what's known as staphylococcal enterotoxin A, or "SEA". Produced by Staphylococcus aureus bacteria, the toxin is a leading cause of food-borne illness in the US and worldwide, according to ARS researcher, Reuven Rasooly.

The ARS test can detect the toxin at levels that are one billion times lower than the current 'gold standard' assay for SEA. The researchers' experiments with chicken, beef and milk indicate that the assay reliably distinguishes active from inactive toxin and yields reproducible results.

The test takes advantage of the fact that the toxin has a double life. Besides causing nausea, vomiting, diarrhoea and other gastroenteritis symptoms, SEA also acts as a superantigen - a molecule that activates large numbers of immune system cells. The assay exploits this trait by measuring proliferation of splenocytes, which are immune system cells produced in the spleen. For the assay, the cells are kept alive in laboratory petri dishes.

The SEA assay is practical, comparatively fast and relatively inexpensive. Experienced technicians can quickly learn how to perform the test using equipment that is standard in laboratories across the nation.