Visual immunoprecipitate assay (VIP) for detection of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in selected foods: collaborative study.

Five foods representative of a variety of food products were analyzed by the Visual Immunoprecipitate Assay (VIP) and the Bacteriological Analytical Manual (BAM) culture method for the presence of Escherichia coli O157:H7. A total of 21 laboratories representing state and federal government agencies, as well as private industry, in the United States and Canada participated. Food types were inoculated with strains of E. coli O157:H7, with the exception of one lot of poultry, which was naturally contaminated. During this study, a total of 1377 samples and controls were analyzed and confirmed, of which 508 were positive and 867 were negative by both methods. Two samples were positive by BAM and negative by VIP. Because of the study design, it was not possible for the BAM method to produce false-negative or false-positive results. The VIP assay for detection of EHEC in selected foods has been adopted first action by AOAC INTERNATIONAL.