Purpose: The objective of this study was to evaluate the Pall GeneDisc® Plate STEC Top 7 (O157, O26, O45, O103, O111, O121 and O145), a PCR-based method for the detection of STEC in 375-g test portions of raw beef trim and ground beef in comparison to the USDA FSIS reference methods using the current AOAC-PTM guidelines.
Methods: The evaluation consisted of inclusivity/exclusivity studies, method comparison of 2 different food matrices (ground beef and beef trim), and ruggedness testing. The performances of the alternate assays were compared to USDA/FSIS MLG 5B.03 (detection of non-O157 STEC) and USDA/FSIS MLG 5.06 (detection of Escherichia coli O157:H7) reference methods. All samples enriched and assayed with the alternate STEC Top 7 method were culturally confirmed by the alternative method confirmation procedure and the USDA/FSIS reference methods.
Results: For the inclusivity study, 50 of the 50 STEC organisms were correctly identified. For the exclusivity study, 30 of the 30 organisms were correctly called negative. For the matrix study, the statistical analysis with POD (Probability of Detection) showed the alternate method to be as good as (for E. coli O157 target) or better than (for the non-O157 STEC targets) the USDA reference method. The complete alternate method was also rugged against variations in incubation temperature, volume of enrichment lysed, and time of lysis of the samples with no statistical difference in the number of positive samples detected.
Significance: This new molecular method was fast and accurate for the detection of STEC Top 7 in beef meat samples.