Purpose: The purpose of this evaluation was to perform inclusivity/exclusivity and an inter-laboratory comparison of the new method in comparison to the reference methods, VRB agar with MUG overlay and alternatively AOAC 991.14 in ground meat, liquid eggs and carcass rinses.
Methods: Methods Peel Plate EC and AOAC 991.14 were evaluated at 35°C for inclusivity using 56 coliform strains. In the exclusivity study, 31 non-coliform strains were studied. In sample comparisons ground-beef, ground-turkey, liquid-egg, chicken rinse and hog-carcass- rinse were fortified at low, medium and high concentrations and split into 5 replicates. Extractions of meats 50 g/450 ml and eggs 100 g/900 ml and rinses were tested in duplicate and compared to reference methods BAM (VBRA/MUG-overlay) and USDA-MLG3.01(AOAC 991.1).
Results: The method detected 55 of 56 coliform strains including all 15 E. coli strains, compared to 41 of 56 coliform, and 14 of 15 E. coli strains, by OMA 991.14. In exclusivity, the new method excluded 28, compared to 26 by the reference, of 31 strains. E. coli strains not producing GLU, mainly hemorrhagic type, were excluded as E .coli but detected as coliform by both methods. For the method comparison, results were evaluated for repeatability (Sr) and by paired t-test for statistical difference, > 0.5 log. The method results were not significantly different from AOAC 991.1 in detecting E. coli and/or coliform. The new method was not significantly different from BAM except with chicken rinse in which E.coli were non-fluorescent because of background flora acidification of plates.
Significance: The method demonstrates high selectivity with comparable E. coli /coliform detection to reference methods for meat and egg matrices.