A Comparative Evaluation of the 3M™ Molecular Detection Assay Salmonella for the Detection of Salmonella in a Variety of Foods

Introduction: The 3M^™ Molecular Detection Assay Salmonella is designed for rapid and specific detection of Salmonellain food, feed and food process environmental samples after 18-24 hours of enrichment. The assay uses a combination of isothermal amplification of unique DNA target sequences and bioluminescence to detect the amplified sequences. Presumptive positive results are reported in real-time while negative results are displayed upon completion of the assay.

Purpose: The purpose of this internal evaluation was to compare the 3M^™ Molecular Detection Assay Salmonellamethod to the FDA/BAM for raw shrimp, bagged spinach and wet-pet food and the USDA/FSIS-MLG method for raw ground beef, cooked breaded chicken and pasteurized liquid whole egg.

Methods: The method comparison was conducted on 6 food matrices by the new method and the FDA/BAM or USDA/FSIS-MLG. Each matrix was inoculated with a different strain of Salmonellaand 20 replicates were analyzed at one inoculum level: 0.2-2 CFU/test portion. Five control replicates were analyzed at 0 CFU/test portion. For the new method, replicates were enriched in BPW (ISO formulation) for 18-24 hours at 37 ± 1°C, DNA was extracted and analyzed by the new assay, and replicates confirmed by the reference methods.

Results: No significant differences were observed between the new method and the reference methods as indicated by McNemar’s X² (> 3.84) for all 6 foods. For foods compared to the FDA/BAM, X² = 1.00 for raw shrimp, 0.41 for bagged spinach and 1.00 for wet pet food. For foods compared to the USDA/FSIS-MLG, X²= 1.71 for raw ground beef, 0.10 for cooked breaded chicken, and 3.49 for pasteurized liquid whole egg.

Significance: For all foods evaluated, the 3M^™ Molecular Detection Assay Salmonella demonstrated comparable results to the reference methods for the rapid, automated detection of Salmonella.