AOAC RI ERP Final Action Recommendations eBook

Dupont BAX Salmonella Pre- Collaborative Study For Expert Review Panel Use Only Do Not Distribute

The BAX® System Real-Time PCR Assay for Salmonella was certified by the AOAC Research Institute in 1 August, 2012 and designated Performance Tested Method SM (PTM) #081201 for testing raw ground beef 2 (25 g and 375 g), chicken carcass rinses, cream cheese, fresh bagged lettuce, dry pet food, and stainless 3 steel. The results of the PTM study demonstrated no significant differences for detection of Salmonella 4 these matrices when comparing the BAX® System method to the standard reference culture procedures 5 described in the U.S. Department of Agriculture-Food Safety and Inspection Service Microbiological 6 Laboratory Guidebook (USDA-FSIS MLG) [1], U.S. Food and Drug Administration Bacteriological 7 Analytical Manual (FDA BAM) [2], and Health Canada Compendium of Analytical Methods (HC CAM) [3] 8 (see attachments “BAX RT Salm AOAC PTM Report Final”). After the PTM approval was achieved, a 9 procedure change was applied to this validation to incorporate an eight-cycle increase in processing 10 time in the BAX® System Q7 instrument (see attachment “Modification Report RT Sal plus 8 cycles Final 11 (3)”). 12 Following the completion of the PTM study and procedure change, a pre-collaborative study was 13 conducted on an additional 18 matrices. The results obtained using the test method indicate no 14 statistical difference when compared to the corresponding reference method results. 15 16 A pre-collaborative study was conducted in accordance with the AOAC INTERNATIONAL Methods 17 Committee Guidelines for Validation of Microbiological Methods for Food and Environmental Surfaces 18 [4] to evaluate the ability of the DuPont™ BAX® System Real-Time PCR Assay for Salmonella to detect 19 the target species in a variety of foods and environmental surfaces. This study was performed by DuPont 20 Nutrition & Health on 18 different sample types to demonstrate the reliability of the test method among 21 a wide variety of sample types. Sample types tested include ground beef with soy, beef trim, 22 frankfurters, shrimp, ground turkey, chicken wings, dried eggs, shell eggs, frozen peas, orange juice, 23 nonfat dry milk, ice cream, peanut butter, cocoa, white pepper, infant formula, ceramic tile, and plastic 24 surfaces. 25 26 Most sample types evaluated in this study were artificially inoculated with a Salmonella strain at levels 27 expected to produce low (0.2–2.0 cfu/test portion) or high (5 cfu/test portion) spike levels on the day of 28 analysis; chicken wings were naturally contaminated. A different Salmonella strain was used for each 29 matrix (see Table 1). All artificial inoculation strains were selected from the DuPont Qualicon Culture 30 Collection or the American Type Culture Collection. To artificially contaminate samples, a pure culture of 31 each strain was grown overnight in BHI broth at 35-37°C, then diluted in additional BHI broth to levels 32 expected to produce fractional positive results based on preparatory studies. Salmonella strains used to 33 inoculate processed foods were heated in a water bath at 55°C for 10 minutes to subject them to heat 34 injury before spiking test samples. 35 Study Design Test Sample Preparation

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