A Matrix Extension and Method Modification of the 3M™ Molecular Detection Assay Salmonella for the Detection of Salmonella Species in a Variety of Foods and Environmental Surfaces

Introduction: Salmonella has been implicated as a main causes of foodborne outbreaks and detection can be time consuming and expensive which results in a strong need for rapid and reliable methods.  The 3M^™ Molecular Detection Assay Salmonella (AOAC OMA 2013.09) is designed for the rapid and specific detection of Salmonella in enriched food, feed and environmental samples, utilizing a combination of isothermal amplification and bioluminescence. This method has been modified to expand its matrix claim and provide same day detection of Salmonella in certain food products.

Purpose: The purpose of this AOAC OMA matrix extension and method modification was to add 11 additional matrices to the method claim (raw ground chicken 25g & 375g, chicken carcass rinsates & sponges, pasteurized American cheese, dry dog food 375g, creamy peanut butter, raw head on shrimp, sprout irrigation water 375g, concrete, ceramic tile and stainless steel) and add a new enrichment protocol to the method: 10 hour enrichment at 41.5°C for raw ground beef (25g, 325g & 375g).

Methods: Each matrix was evaluated by the new method and the FDA/BAM or USDA/FSIS-MLG at the following inoculation levels: 20 replicates at 0.2-2 CFU/test portion, 5 replicates at 2-5 CFU/test portion, and 5 replicates at 0 CFU/test portion. New matrices were evaluated after 18 hours of primary enrichment. Raw ground chicken was analyzed at 14 hours for 325g and 10 hours for 25g test portions. Raw ground beef test portions were evaluated after 10 hours of enrichment at 41.5°C. Results for each matrix were analyzed using the POD statistical model.

Results: No statistically significant differences were observed between the new method and reference methods for each new food or for the method modification.

Significance: The new method demonstrated high sensitivity and specificity for the detection of Salmonella in the new matrices and with the new enrichment protocol.