Many staphylococcal strains produce enterotoxin, the toxin that is the cause of staphylococcal food poisoning. If a strain is enterotoxigenic it is possible for it to be involved in food poisoning. The gel diffusion methods were the first methods developed for detection of the enterotoxins and were thought adequate to detect their production. However, they were not adequate to detect enterotoxin in foods involved in food poisoning. When researchers began using the sensitive methods, such as enzyme-linked immunosorbent assay (ELISA) and reversed passive latex agglutination (RPLA), to check strains for enterotoxin production, some strains produced nanogram quantities of enterotoxin. When it was reported that several coagulase-negative species produced less than 10 ng/ml of enterotoxin, it was imperative to determine whether these strains produced enough enterotoxin in foods to cause food poisoning. At the present time research is under way to determine whether these strains produce enough enterotoxin in foods to cause food poisoning.