Microbiology Methods for ERP Review 3-2020

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Results of Collaborative Study

The collaborative study involved a method comparison evaluation of the Solus One Salmonella immunoassay to the FDA/BAM Chapter 5 reference method for instant non-fat dry milk. A total of 14 participants throughout the continental United States, Mexico, South Africa, Germany and the United Kingdom participated in this study. In 2 of the laboratories, 2 separate analysts participated, while the remaining 12 laboratories each had 1 participating analyst. Out of the 14 participants, 12 participants submitted data. One laboratory voluntarily withdrew from participation prior to initiating testing. Another laboratory was unable to participate due to a delay with customs, resulting in missing the deadline to initiate testing. The final laboratory had unacceptable data due to gross cross contamination for all test portions that were analyzed. The root cause of the contamination was not determined. For the laboratories that did participate, each participant analyzed 36 unpaired test portions for the Solus One Salmonella assay and the FDA/BAM Chapter 5 reference method: 12 inoculated with a high level of Salmonella , 12 inoculated with a low level of Salmonella , and 12 uninoculated controls. In addition to the test portions, all participants set up an aerobic plate count (APC) to determine the total microbial load of test matrix and the appropriate incubation conditions for the TT broth. The average APC result obtained by the collaborators was 5.2 x 10 2 CFU/g. The highest count documented out of all of the participants was 2.2 x 10 3 CFU/g and the lowest was 1.0 x 10 2 CFU/g. A background screen, following the FDA/BAM Chapter 5 reference method, of the matrix indicated an absence of indigenous Salmonella species. Ten (10) replicate 375-gram test portions (randomly sampled from 50% of the total packages used in the analysis) were screened for the presence of Salmonella . All test portions produced negative results for the target analyte. Table 2020.01A summarizes the inter-laboratory results. As per criteria outlined in Appendix J of the AOAC Validation Guidelines, fractional positive results were obtained. Detailed results for each laboratory are presented in Tables 2020.01B . The level of Salmonella was determined by MPN on the day of initiation of analysis by the coordinating laboratory. The MPN levels obtained, with a 95% confidence interval, were 0.45 CFU/test portion (0.34, 0.59) for the low inoculum level and 5.44 CFU/test portion (2.50, 19.54) for the high inoculum level. MPN results are presented in the second column of Table 2020.01B . Detailed results of the LPOD statistical analysis are presented in Table 2020.01B and Figures 1A-1B. For the low inoculation level, 57 out of 132 test portions (LPOD CP of 0.43) were reported as presumptive positive by the Solus One Salmonella with 58 out of 132 test portions (LPOD CC of 0.44) confirming positive (following both the alternative confirmation and the FDA/BAM Chapter 5 reference method). For samples that produced presumptive positive results by the Solus One Salmonella , 57 out of 132 samples confirmed positive (LPOD C of 0.43; value include Instant Non-Fat Dry Milk

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