Validation of PhageDx(™)Salmonella Assay in Raw Ground Turkey and Powdered Infant Formula: AOAC Performance Tested Method(SM) 121904

BACKGROUND: The PhageDx(™)Salmonella Assay is based on the infection of Salmonella spp. by specific bacteriophages and expression of a luciferase reporter gene. Results are generated in as little as 9.5 h for raw ground turkey and 18.5 h for milk-based powdered infant formula (PIF). OBJECTIVE: An AOAC Performance Tested Methods(SM) (PTM) study was conducted to validate the PhageDx Salmonella Assay for the detection of Salmonella in 25 g raw ground turkey and 100 g PIF test portions. METHOD: The performance of the PhageDx Salmonella Assay was compared to that of the U.S. Department of Agriculture (USDA), Food Safety and Inspection Service (FSIS) Microbiology Laboratory Guidebook (MLG) 4.10 for raw ground turkey and the U.S. Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Chapter 5 for PIF. Inclusivity/exclusivity, product consistency and stability, and robustness testing were conducted. RESULTS: There was no significant difference between the 25 g raw ground turkey and 100 g PIF PhageDx Salmonella Assay and the USDA/FSIS MLG 4.10 and FDA/BAM Chapter 5, respectively. The reporter bacteriophages were specific for Salmonella and infected 108 strains in inclusivity testing. They did not infect 30 non-Salmonella bacteria in exclusivity testing. Robustness testing showed that the method performed well with specific deviations from the standard protocol. Consistency and stability testing demonstrated that the recombinant phage gave consistent results across three production lots and was stable when stored under appropriate conditions for at least eight months. CONCLUSIONS: The data collected in the validation study demonstrate that the PhageDx Salmonella Assay meets the qualifications for PTM status. HIGHLIGHTS: The PhageDx Salmonella Assay is a rapid, specific, sensitive assay capable of detecting a wide range of Salmonella spp. with a significantly shorter turn around time than the USDA/FSIS and FDA reference methods.