AOAC ERP MICRO AUGUST 2018

94 B ird et al .: J ournal of AOAC I nternational V ol . 100, N o . 1, 2017 assay for any Inspect samples. If the result continues to read “Inspect,” proceed to the confirmation test using your preferred method or as specified by local regulations.

but were unable to conduct the analysis, and, therefore, no data submitted. All other collaborating laboratories submitted data for both methods under evaluation. The MPN levels obtained for this matrix with 95% confidence intervals were 0.63 CFU/test portion (0.49, 0.80) for the low inoculum level and 4.52 CFU/test portion (3.19, 6.42) for the high inoculum level. For the low inoculum level, 68 of 132 test portions (POD CP of 0.52) were reported as presumptive positive by the 3M MDA 2– Listeria method, with 66 of 132 test portions (POD CC of 0.50) confirming positive. For samples that produced presumptive positive results on the 3M MDA 2– Listeria method, 66 of 132 samples confirmed positive (POD C of 0.50). For test portions evaluated by the USDA/FSIS MLG 8.09 reference method, 60 of 132 test portions produced positive results. A dLPOD C value of 0.04 with 95% confidence intervals of (–0.08, 0.17) was obtained between the candidate and reference methods, indicating the difference between methods was not statistically significant at the 0.05 probability level. A dLPOD CP value of 0.02 with 95% confidence intervals of (–0.11, 0.14) was obtained between presumptive and confirmed results, indicating the difference between presumptive and confirmed results was not statistically significant at the 0.05 probability level. For the high inoculum level, 132 of 132 test portions (POD CP of 1.00) were reported as presumptive positive by the 3M MDA 2– Listeria method, with 132 of 132 test portions (POD CC of 1.00) confirming positive. For samples that produced presumptive positive results on the 3MMDA2– Listeria method, 132 of 132 samples confirmed positive (POD C of 1.00). For test portions evaluated by the USDA/FSIS MLG 8.09 reference method, 132 of 132 test portions produced positive results. A dLPOD C value of 0.00 with 95% confidence intervals of (–0.03, 0.03) was obtained between the candidate and reference methods, indicating the difference between the methods was not statistically significant at the 0.05 probability level. A dLPOD CP value of 0.00 with 95% confidence intervals of (–0.03, 0.03) was obtained between presumptive and confirmed results, indicating the difference between presumptive and confirmed results was not statistically significant at the 0.05 probability level. For the uninoculated controls, 0 of 132 samples (POD CP of 0.00) produced a presumptive positive result by the 3M MDA 2– Listeria method with 0 of 132 test portions (POD CC of 0.00) confirming positive. For samples that produced presumptive positive results on the 3M MDA 2– Listeria method, 0 of 132 samples confirmed positive (POD C of 0.00). For test portions evaluated by the USDA/FSIS MLG 8.09 reference method, 0 of 132 test portions produced positive results. A dLPOD C value of 0.00 with 95% confidence intervals of (–0.03, 0.03) was obtained between the candidate and reference methods, indicating the difference between methods was not statistically significant at the 0.05 probability level. A dLPOD CP value of 0.00 with 95% confidence intervals of (–0.03, 0.00) was obtained between presumptive and confirmed results, indicating the difference between presumptive and confirmed results was not statistically significant at the 0.05 probability level. Detailed results of the POD statistical analysis are presented in Table 2016.07C and Figure 1A and B. (b)  Raw chicken breast fillet (25 g test portions) . — Raw chicken breast fillet test portions were inoculated at a low and high inoculum level and analyzed for the detection of Listeria spp. Uninoculated controls were included in each analysis. Laboratory 11 did not participate in the evaluation of this matrix. Laboratory 10 submitted data that indicated cross-contamination

Results of the Collaborative Study

For this collaborative study, the 3M MDA 2– Listeria method was compared with the USDA/FSIS MLG 8.09 reference method for deli turkey and raw chicken breast fillet. A total of 13 laboratories throughout the United States and Canada participated in this study, with 11 laboratories submitting data for the deli turkey and 12 laboratories submitting data for the raw chicken breast fillet. See Table 2 for a summary of laboratory participation for each matrix. Each laboratory analyzed 36 test portions for each method per matrix: 12 inoculated with a high level of Listeria , 12 inoculated with a low level of Listeria , and 12 uninoculated controls. A background screen of the matrix indicated an absence of indigenous Listeria species in both matrixes. Ten replicate test portions (randomly sampled from 50% of the total packages used in the analysis) were screened for the presence of Listeria species. All test portions produced negative results for the target analyte. Results for the heat-stress analysis of the inoculum for the deli turkey are presented in Table 1. The raw chicken breast fillet was not heat-treated, therefore it was not necessary to injure the cells. Tables 2016.07A and 2016.07B summarize the interlaboratory results for all foods tested, including POD statistical analysis. As per criteria outlined in Appendix J of the AOAC validation guidelines (4), fractional positive results were obtained. Detailed results for each laboratory are presented in Tables 2016.07C and 2016.07D . For each matrix, the level of Listeria was determined by MPN on the day of initiation of analysis by the coordinating laboratory. MPN results are presented in Tables 2016.07C and 2016.07D . The individual laboratory and sample results are presented in Tables 1 and 2 in Supplemental Information . (a)  Deli turkey (125g test portions) . — Deli turkey test portions were inoculated at a low and high level and were analyzed for the detection of Listeria spp. Uninoculated controls were included in each analysis. Laboratories 8 and 10 received test portions Table 2. Participation of each collaborating laboratory a,b Lab Deli turkey Raw chicken breast fillet 1 Y Y 2 Y Y 3 Y Y 4 Y Y 5 Y Y 6 Y Y 7 Y Y 8 N Y 9 Y Y 10 N Y 11 Y N 12 Y Y 13 Y Y a  Y=The collaborator analyzed the food type. b  N=The collaborator did not analyze the food type.

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