Colorimetric and fluorometric substrate immunoassays for detection of Salmonella in all foods: comparative study

Two modified fluorescent enzyme immunoassays for the detection of Salmonella in food have been developed. Both of the new procedures, which substitute a colorimetric substrate for the fluorescent substrate and in which results are read visually or with a photometer, are modifications of AOAC method 989.15. The visually read procedure uses the same antibody-coated wells as in method 989.15. The colorimetric end point of the assay is determined by comparing the solution color to a color chart. The assay result may also be read in a photometer, if the solution is first transferred to a transparent microtiter well. The second procedure designed to be read in a photometer substitutes clear, antibody-coated wells for those used in the fluorescent assay. The colorimetric assays employ identical monoclonal antibodies for capture and detection of Salmonella as used in the fluorescent assay. In this comparative study, the performance of each new assay was consistent with the performance of method 989.15. These methods have been adopted official first action by AOAC as alternative methods for the detection of Salmonella in foods.