Enzyme immunoassay of staphylococcal enterotoxins in dairy products with cleanup and concentration by immunoaffinity column

Two different immunoaffinity columns (IACs) were prepared for detection of staphylococcal enterotoxins (SETs) from dairy products. First, a specific I AC for staphylococcal enterotoxin A (SEA)., IAC-1, was prepared by coupling monoclonal antibody (mAb) directed against SEA; second, a polyspecific IAC for SEA, staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SECs), and staphylococcal enterotoxin D (SED), IAC-2, was prepared by coup ling a mixture of mAbs against SEA, SECs, and SED, and rabbit IgG against S EB. These columns were applied for detection of SETs in dairy products, aft er extraction, immunoaffinity chromatography, and enzyme immunosorbent assa y (EIA). Overall recoveries from dairy products spiked with 1 ng SEA/25 g a veraged 81.2% (range, 76-85%) on IAC-1. The repeated use of IAC-1 was then determined with good efficiency of 91.5%, in more than 10 runs. On the othe r hand, a recovery yield of 77% of SETs (SEA, SEB, SEC, and SED) from dairy products spiked with 2.5 ng of each enterotoxin per 25 g, was obtained wit h IAC-2. IAC-2 was also successfully subjected to the chromatography of nat urally contaminated foods implicated in staphylococcal food poisoning outbr eaks. This new extraction-concentration-immunoaffinity-chromatography metho d (ECIC) is very useful for improving staphylococcal enterotoxin detection and eliminating matrix effect in EIA of dairy products.