Comparison of Two Enzyme Immunoassays for Recovery of Salmonella spp. from Four Low-Moisture Foods

Abstract

Two enzyme immunoassays (Salmonella-Tek™ and Report™) were compared with the standard culture method of the Association of Official Analytical Chemists (AOAC) and the Food and Drug Administration's Bacteriological Analytical Manual (BAM) for the recovery of Salmonella spp. from four low-moisture foods. Two protocols were used to compare the effectiveness of the two immunoassays: i) foods were contaminated in the dry state; or ii) serial tenfold dilutions of Salmonella spp. were inoculated into the postenrichments after incubation. Of three hundred 25-g test portions inoculated in the dry state, 199 gave confirmed positive reactions with the Salmonella-Tek™ assay, 193 with the Report™ assay, and 206 with the AOAC/BAM method. There were seven false-negative reactions with Salmonella-Tek™ and 13 false negatives with the Report™, a false negative being defined as one that was negative by the enzyme immunoassay but was confirmed positive by the AOAC/BAM culture method. When the postenrichments were inoculated after incubation, a lower number of cells gave a positive assay result with the Salmonella-Tek™ system than with the Report™ system, indicating greater sensitivity