Dose–response curves of MagPlex microspheres detecting E. coli in multiplexed assays in matrices: a PBST, b spinach, c chicken wash, and d milk. Concentrations are reported in colony forming units per milliliter. Microsphere sets are coated with antibodies to the antigens indicated using the following code: E. coli (square), Salmonella (diamond), Campylobacter (triangle), Listeria (circle), SEB (cross)