4. AOACRIMicroMethods-2018Awards

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B ird et al .: J ournal of AOAC I nternational V ol . 100, N o . 2, 2017  465

Figure 2016.08B 

(randomly sampled from 50% of the total packages used in the analysis) were screened for the presence of L. monocytogenes . All test portions produced negative results for the target analyte. Results for the heat stress analysis of the inoculum for deli turkey are presented in Table 1. A 60.8% injury rate was determined. The raw chicken breast fillet is not heat-treated; therefore, it was not necessary to injure the cells. Tables 2016.08A and 2016.08B summarize the interlaboratory results for all foods tested, including LPOD statistical analysis. As per the criteria outlined in Appendix J of the AOAC INTERNATIONAL Methods Committee Guidelines for Validation of Microbiological Methods for Food and Environmental Surfaces (4), fractional positive results were obtained. Detailed results for each laboratory are presented in Tables 2016.08C and 2016.08D . For each matrix, the level of L. monocytogenes was determined by MPN testing on the day of initiation of analysis by the coordinating laboratory. MPN results are presented in Tables 2016.08C and 2016.08D . The individual laboratory and sample results are presented in supplemental Tables 1 and 2. The APC results for each collaborating laboratory are presented in supplemental Table 3. Deli turkey (125 g test portions) . — Deli turkey test portions were inoculated at a low and a high level and analyzed for the detection of L. monocytogenes . Uninoculated controls were included in each analysis. Laboratories 8 and 10 received test portions but were unable to conduct the analysis and, therefore, Table 2. Participation of each collaborating laboratory a Laboratory 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 = Collaborating laboratory analyzed the food type; N = collaborating laboratory did not analyze the food type.

Always dispose of sealed reagent tubes by soaking in a household bleach solution (1–5%, v/v in water; 5250–6500 ppm) for 1 h and away from the assay preparation area.

J. Results and Interpretation

An algorithm interprets the light output curve resulting from the detection of the nucleic acid amplification. Results are analyzed automatically by the software and are color-coded based on the result. Apositive or negative result is determined by analysis of a number of unique curve parameters. Presumptive positive results are reported in real time, whereas negative and “inspect” results will be displayed after the run is completed. Presumptive positive samples should be confirmed as per the laboratory’s standard operating procedures or by using the current version of the appropriate reference method confirmation (FDA/BAM or USDA/FSIS-MLG), beginning with transfer from the primary enrichment to the secondary enrichment broth (if applicable), followed by subsequent plating and confirmation of isolates using appropriate biochemical and serological methods. Note : Even a negative sample will not give a zero reading because the system and 3M MDA 2 – Listeria monocytogenes amplification reagents have a “background” relative light unit reading. In the rare event of any unusual light output, the algorithm labels this as inspect. 3M recommends the user to repeat the assay for any inspect samples. If the result continues to be inspect, proceed to confirmation testing using your preferred method or as specified by local regulations. For this collaborative study, the 3M MDA 2 – Listeria monocytogenes method was compared to the USDA/FSIS MLG 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 L. monocytogenes , 12 inoculated with a low level of L. monocytogenes , and 12 uninoculated controls. A background screen of the matrix using the USDA/FSIS MLG reference method indicated an absence of indigenous L. monocytogenes in both matrixes. Ten replicate test portions Results of Collaborative Study

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