Purpose: The purpose of this AOAC OMA Collaborative Study was to compare the assay to the FDA/BAM for wet pet food (375 g) and the USDA/FSIS-MLG for raw ground beef (25 g).
Methods: This new method was compared in a multilaboratory collaborative study to the FDA/BAM Chapter 5 method and the USDA MLG 4.05 method. Each matrix was artificially contaminated with Salmonella at 3 inoculation levels: a low-level inoculum of 0.2-2 CFU/test portion, a high-level inoculum 2-5 CFU/test portion and an un-inoculated control level 0 CFU/test portion. A total of 20 laboratories representing government, academia and industry, throughout the United States, participated.
Results: In this study, 1,512 samples were analyzed, of which 756 were analyzed by the assay and 756 were analyzed by either the USDA/FSIS-MLG or FDA/BAM reference method. Of the 1,512 unpaired replicates, 387 were presumptive positive by the MDA Salmonella method, with 383 confirmed positive samples. There were 389 confirmed positive replicates by the USDA/FSIS-MLG or FDA/BAM reference methods. Statistical analysis was conducted according to the Probability of Detection (POD) and the Relative Limit of Detection (RLOD) and no statistically significant difference was observed between the new and reference methods.
Significance: For all foods evaluated, the MDA Salmonella assay demonstrated comparable results to the reference methods for the rapid detection of Salmonella in as little as 18 hours of enrichment.