A collaborative study comparing three ELISA systems for detecting Staphylococcus aureus enterotoxin A in sausage extracts

Three ELISA's for the detection of staphylococcal enterotoxin A (SEA) were evaluated by a collaborative test in five laboratories for possible use in quality control laboratories. Two ELISA's gave quantitative results using polyclonal antibodies (PCA) or monoclonal antibodies (MCA); the third was the commercially available qualitative FEY ELISA test using PCA. Test samples comprised ripened and unripened sausage alone or spiked with 10 μg or 1 μg SEA/100 g, the latter representing a minimum emetic dose. The quantitative MCA ELISA gave more reliable and sensitive results with lower non-specific background responses, lower standard deviations and coefficients of variation than the PCA ELISA; however, the recovery of enterotoxin concentrations from extracts was lower, which was more distinct in unripened than in ripened sausage. The MCA ELISA gave lower values of absolute response but more reliable results for extracts from sausage spiked with 1 μg SEA/100 g. The FEY ELISA gave sufficient reliable results in our experiments with sausage extracts and looks adequate for controlling suspicious raw materials and food products.