AOAC-RI ERP Micro June 2016

OMAMAN-29/OMAMAN-30 Combined Collaborative Study Protocol OMA ERP - June 2016 ERP Use Only

3M MDA 2 Listeria species and L. monocytogenes Collaborative Study OMA-2016-MONTH-XXX

performed starting with the secondary enrichment steps. The recovered isolates will be identified by the API Listeria Identification System or the VITEK 2 GP (AOAC OMA 2012.02). One additional control (negative) test portion will be provided to each collaborator for each matrix to determine the total plate count on the day of analysis. 3.6 Most Probable Number (MPN) Analysis. To determine the level of Listeria spp. in the inoculated food test portions on the day of initiation of analysis, a 5- tube MPN determination is performed by the coordinating laboratory following the appropriate reference method. The level of Listeria will be determined by Most Probable Number (MPN) on the day of analysis by analyzing 5 x 50 g, 20 x 25 g (reference method test portions) and 5 x 10 g inoculated test samples for raw chicken breast. For the 125 g deli turkey test portion analysis, 5 x 250 g, 20 x 125 g (reference method test portions) and 5 x 60 g test portions will be analyzed. Each test portion will be enriched with the appropriate reference method enrichment broth at a 1:10 dilution and analyzed by the reference method procedure. The number of positives from the three test levels will be used to calculate the MPN using the MPN calculator. ( http://www.lcfltd.com/customer/LCFMPNCalculator.exe)[1 ]. Report MPN as MPN/test portion. For the detection of Listeria species from: 4.1.1 Beef hot dogs (25 g and 125 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.2 Cold smoked salmon (25 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.3 Deli turkey (25 g and 125 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.4 Full fat cottage cheese (25 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.5 Queso fresco (25 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.6 Vanilla ice cream (25 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.7 Bagged raw spinach (25 g): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.8 Cantaloupe (whole melon): 24-30 hours of enrichment in Demi Fraser broth at 37°C 4.1.9 Raw chicken leg pieces (25 g): 28-32 hours of enrichment in Demi Fraser broth at 37°C AOAC Research Institute Expert Review Panel Use Only 3M MDA2 - Listeria species 4.1 Applicability

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5/4/16