Methods to Detect pathogen and toxin in Food

Methods Detect Pathogens and Toxins in Food
Antibodies are protein molecules that bind to antigens—such as bacteria—and remove them from the body. Researchers can use antibodies to isolate pathogens or chemicals in food products as well.

There is a procedure that combines immunomagnetic capture with TRF to simultaneously detect Escherichia coli and Salmonella in ground beef, ground turkey, alfalfa sprouts, and seeds. The procedure uses magnetic beads that are coated with pathogen-specific antibodies. The antibodies bind to the bacteria, and the magnetism pulls them out of complex mixtures of food. Once extracted, the bacteria can be more easily detected.

A luminescence-based method coupled with an ELISA (enzyme-linked immunosorbent assay) is to detect and confirm E. coli O157:H7. An ELISA is a sensitive laboratory test that uses antibodies and enzymes to detect and measure specific antigens in samples. The test can be completed in 8 hours and can detect 1-10 bacteria per gram of ground meat. USDA's Food Safety Inspection Service (FSIS) would ultimately like to be able to detect 1 bacterium in 25 grams of meat.

There is a biosensor immunoassay using surface plasmon resonance (SPR) to detect Staphylococcus aureus enterotoxin A (SEA) and B (SEB)-toxins that cause gastroenteritis—in foods such as ham, milk, and eggs. Conventional heating and processing kills the bacterium but not its toxins. Bacteria produce toxins under stressful conditions, such as when they are too crowded or denied food or when they're fighting back against antibiotics.
SPR uses light reflected off thin metal films. Toxin molecules in the sample bind to the sensor surface, and the refractive index at the surface changes. The time it takes for a response from the interaction provides a measure of how much toxin, if any, is actually present in the food sample.

Latex particle agglutination assay is developed for detection of SEA and SEB that causes the toxins to clump together. The method takes advantage of an antibody's ability to bind to a unique antigen in pathogen cells. The assay is simpler to use than other methods and can detect as little as 10 parts per billion of toxin per gram of sample.