ARS develops technique to detect toxins, improve food safety

01/11/2005

A new technique to improve food safety that detects heat-resistant toxins in foods such as ham, milk and eggs has been developed by USDA's Agricultural Research Service (ARS). The technique may help researchers and inspectors detect toxins that cause gastroenteritis. In addition to detecting bacteria and their toxins, methods are being developed to screen, detect and confirm multiple chemical residues -- such as veterinary drugs and pesticides -- in food products.

Bacteria produce toxins under stressful conditions, such as when they are too crowded, denied food or fighting back against antibiotics. Generally, conventional heating and processing kill food-borne bacteria but do not destroy their toxins.

Marjorie B. Medina, a research chemist at the ARS Eastern Regional Research Center in Wyndmoor, Pa., developed a biosensor-based method that detects chemical signals from toxin-producing bacteria and provides information about their specific biological activities.

Medina focused on Staphylococcus aureus enterotoxins A and B. The biosensor test uses surface plasmon resonance (SPR) to detect toxins. SPR uses light reflected off thin metal films. Attached to these films are toxin or antitoxin antibody molecules. When these molecules bind to the film surface, they change the way light refracts. These changes in light intensity, monitored by an optical detector, provide a measure of how much toxin, if any, is present in a food sample.

Medina's semi-automated method will be able to detect several bacterial toxins in a single food sample.

For more information on this research, go to www.ars.usda.gov/is/AR/archive/jan05/food0105.htm