Detection of Salmonella with the BioEnzabead™ Enzyme Immunoassay Technique

The performance of the double-antibody (MOPC 467 and 6H4) BioEnzabead™ enzyme linked immunosorbent assay was evaluated with pure cultures and naturally contaminated foods. The immunoassay detected all but four (1.6%) of the 250 Salmonella test strains and showed high levels of cross-reactivity (30.7%) among the 75 strains of non salmonellae examined. Citrobacter freundii figured prominently as a source of erroneous results. Although the BioEnzabead™ system identified the 41 foods found to be contaminated by a standard cultural procedure, a high rate of false positive reactions (46%) was nevertheless encountered with high moisture foods. Attempt at method brevity through application of the immunoassay at the preenrichment level was unsuccessful resulting in the detection of only 24 (58.5%) of the 41 contaminated foods. Greater recoveries were obtained with tetrathionate brilliant green enrichment broth incubated at 43°C than at 35°C.