P3-38 Validation of a Commercial Real-time PCR Test Kit for Screening Salmonella in Produce, Meats, Seafood, Dairy, Spices, Infant Formula, Pet Food and Environmental Surfaces

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Morgan Wallace, DuPont Nutrition and Health, Wilmington, DE
Bridget Andaloro, DuPont, Wilmington, DE
Stephen Varkey, DuPont, Wilmington, DE
Daniel DeMarco, DuPont, Wilmington, DE
Dawn Fallon, DuPont, Wilmington, DE
Nisha Corrigan, DuPont, Wilmington, DE
Andrew Farnum, DuPont Qualicon, Wilmington, DE
Monica Tadler, DuPont, Wilmington, DE
Steven Hoelzer, DuPont Nutrition and Health, Wilmington, DE
Julie Weller, DuPont Nutrition and Health, Wilmington, DE
George Tice, DuPont, West Deptford, NJ
Patrick Bird, Q Laboratories, Inc., Cincinnati, OH
Erin Crowley, Q Laboratories, Inc., Cincinnati, OH
Introduction: Salmonella is found in many food and environmental sources and causes serious illness. Since its isolation can be long and difficult non-culture, rapid methods for its detection are needed.

Purpose: This study evaluated the DuPont™ BAX<sup>®</sup> System Real-Time PCR Assay for Salmonella for detecting Salmonella spp. across a diverse range of food and environmental matrices. 

Methods: A total of 24 sample types were evaluated from categories including produce, meats, seafood, eggs, dairy, spices, infant formula, pet food and environmental surfaces. Most matrices were spiked at a level sufficient to give fractional results, while two matrices (poultry rinsates and chicken wings) were naturally contaminated with Salmonella at fractional levels. For samples for which the enrichment protocols differ between the test method and the reference FDA-BAM, USDA-MLG and/or Health Canada Compendium methods, the reference culture method was also performed on comparable samples enriched using the appropriate reference method enrichment protocol. Most test samples were evaluated with the PCR method before and after a 3-hour secondary enrichment (re-growth) in BHI broth to help ensure that variants of each food type could be tested using this method, even if the grow-back step is required.

Results: In this study 788 presumptive positive results were obtained from 1815 total tests with the PCR test method from either the primary enrichment or the BHI re-growth. Sensitivity and specificity were calculated to be >99.9% for the alternative PCR method when compared against the appropriate culture method results.  Analysis using the AOAC International POD model demonstrated no statistically significant difference between alternative and reference culture methods.  

Significance: This study demonstrates that the Assay for Salmonella is a rapid and sensitive alternative method for detecting Salmonella in these matrices using both standard and alternative enrichment methods. Test method results demonstrated no significant difference when compared with the corresponding reference culture methods.