DEVELOPMENT AND EVALUATION OF A RAPID ENZYME-LINKED IMMUNOFILTRATION ASSAY (ELIFA) AND AN ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA) FOR THE DETECTION OF STAPHYLOCOCCAL ENTEROTOXIN B

An enzyme-linked immunofiltration assay (ELIFA) and a microtitre plate enzyme-linked immunosorbent assay (ELISA) were developed and compared for their ability to detect staphylococcal enterotoxin B (SEB). The double antibody capture format was used for both assays. Factors which improved the sensitivity of the ELIFA system were (1) addition of casein and thimerosal to the antigen dilution buffer; (2) addition of polyethylene glycol (MW 6000) to the detection and conjugate antibody dilution buffers; and (3) washing with diethanolamine buffer prior to addition of the substrate/chromogen. The ELIFA system had a turnaround time of approximately 1 h and a detection limit of 1 ng/mL of purified SEB. The ELISA had a total turnaround time of 21 h, or 3 h using plates pre-coated overnight with the capture antibody. The detection limit of the ELISA for purified SEB was 0.05 ng/mL. The detection limit of SEB in cheese samples spiked with purified enterotoxin and subjected to a simple extraction procedure was 1 ng/mL and 0.1 ng/mL of extract, with the ELIFA and the ELISA, respectively.