[Determination of staphylococcal enterotoxins A, B, C and D in foods using sandwich ELISA with labeled antibody].

Abstract

The noncompetitive Sandwich-ELISA (polystyrene balls) with labelled antibody for staphylococcal enterotoxins (SE) A, B, C, and D according to Fey et al. (1984), which have recently been introduced commercially, was applied to analysis of foods. The effect of various food ingredients on the quantitative determination and recovery of SE was investigated. The unspecific effect of food components which, in some cases, caused false-positive results in the competitive ELISA was less frequent. Nevertheless, the differences in binding of unlabeled antigen between buffer and food were still observed. Using ELISA microtiter plates the effect of food components was less pronounced. Enterotoxin type A or a mixture of A and D were dominant in foods which were involved in food poisoning (about 150 samples). In meat the recovery of SE added (1-10 ng/g) ranged from 30-60%. The assay sensitivity in buffer ranged from 0.1 ng/ml for enterotoxins A, B, C and D (5 ml sample) to 0.2 ng/ml for enterotoxins A-D (1 ml sample) using polystyrene balls and was 1 ng/ml for enterotoxins A-D using ELISA plates. In foods the detection limit was occasionally higher. The required sensitivity for enterotoxin A (maximum limit 1 ng/g) could mostly be reached. Because of the differences in antigen binding in buffer and in various food extracts the determination of the enterotoxin content in this range is laborious.