Micro December 2018

b. ISO defines coliforms by their ability to grow in method-specific, selective media. ISO 48324 enumerates typical coliform colonies on Violet Red Bile Lactose (VRBL) agar, with confirmation of atypical colonies. Enumerate red colonies with and without gas production. The total coliform count is indicated by red colonies with or without gas production and blue colonies with and without

1 2 3 4 5 6 7 8 9

gas production, the countable range is 1-100 CFU.

9. Multiply the count by the dilution factor to get final coliform and E. coli count.

Results of the Collaborative Study 10 In this collaborative study, the 3M Petrifilm Rapid E. coli /Coliform Count Plate was compared to 11 the FDA BAM Chapter 4, ISO 4832-1 and 16649-2 for the enumeration of E. coli and coliform. 12 A total of 9 participants across 8 laboratories throughout the United States, Canada, Mexico and 13 Switzerland participated in the evaluation. All participants who received samples performed 14 analysis and submitted results. 15 16 The candidate method results along with the reference method results reported by each 17 laboratory were converted to logarithmic values for statistical analysis and were plotted using a 18 Youden’s plot. The Log 10 individual laboratory results are presented in Tables 1-5. Figures 1-5 19 present the Youden plots of each matrix. The transformed data were analyzed for outliers by the 20 Cochran and Grubb’s tests. No outliers were identified. The difference of means (including 95% 21 confidence intervals), repeatability (s r ) and reproducibility (s R ) were determined for each 22 contamination level. The results of the interlaboratory data analyses are presented in Table 23 2018.1A-1B. In addition to the test portions, each participant that performed testing submitted 24 results for an Aerobic Plate Count (APC) test to determine the total microbial load of the test 25 matrix. The average APC result obtained by the collaborators was 1.8 x 10 5 CFU/g (low to high 26 range of 3.4 x 10 4 CFU/g to 5.2 x 10 5 CFU/g). Table 6 presents the results of the APC for each 27 collaborator. Four contamination levels were evaluated (uninoculated, low, medium and high) by both the 32 candidate and reference method. Nine collaborators submitted data, and all data sets were 33 included in the statistical analysis. 34 35 3M Petrifilm Rapid E. coli/Coliform Count Plate & BAM Coliform 38 and high contamination levels, indicated that no statistically significant difference existed 39 between the candidate and reference method. Repeatability (0.00, 0.22, 0.12 and 0.10) and 40 reproducibility (0.00, 0.25, 0.16 and 0.17) values for each contamination level indicate that the 41 method performed similarly within sample replicates and between laboratories throughout the 42 range of contamination levels. 43 44 3M Petrifilm Rapid E. coli/Coliform Count Plate & BAM E. coli 47 and high contamination levels, indicated that no statistically significant difference existed 48 36 37 Difference of means values (0.00, -0.28, 0.28 and 0.17) for the uninoculated, low, medium 45 46 Difference of means values (0.00, -0.02, -0.01 and -0.02) for the uninoculated, low, medium 28 29 30 31 Dry Dog Kibble

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