A sandwich ELISA method for detection of Staphylococcus aureus enterotoxins

Staphylococcus aureus enterotoxins A, B, and C, were detected by means of a four-layer sandwich ELISA method. With toxin produced in broth supernatants, this ELISA method had a detection limit of 0.5 ng enterotoxin per ml. Conjoint with enterotoxin, S. aureus most often produces protein A. The protein A will interfere and produce false positive reactions in a sandwich ELISA, by binding nonspecifically the IgG in different layers, simulating the immunospecific toxin binding. With rabbit IgG coupled to Sepharose CL-4B gel, 99% of protein A could be removed from solutions, bringing the level under the interfering limit in the ELISA.