Assurance Escherichia coli O157:H7 : A comparative validation study

A wide variety of food products, with emphasis on raw meat products, were analyzed simultaneously by 3 methods: the Assurance Escherichia coli O157:H7 (EHEC) enzyme immunosorbent assay (EIA), the EHEC visual immunoprecipitate assay (VIP), and a modified Bacteriological Analytical Manual (BAM) culture method. This paper reports results of a comparative study of the Assurance and modified BAM methods. In this comparative study, 1050 samples and controls gave false-negative rates of 1.0 and 0%, respectively, for the Assurance EIA and the modified BAM culture methods. The overall agreement between the 2 methods was 99.4%. Cultural confirmation of presumptive positive samples was problematic because competitive flora were present in higher levels than EHEC in the enrichment broth after incubation and the target organism had nondescript characteristics on the primary selective agar, hemorrhagic coli agar, which necessitated picking of additional colonies in many instances.