Detection of Salmonella in Powdered Gelatin: Comparison of 3M Molecular Detection Assay – Salmonella and 3M Molecular Detection Assay 2 – Salmonella to the Australian Standard Method (ISO 6579)

Introduction: The 3M Molecular Detection System utilizes a combination of isothermal DNA amplification and bioluminescence to detect targeted pathogens. A new generation of the assay utilizes proprietary nanotechnology to bind inhibitory substances, allowing for faster assay times and improved workflows. Previously the system has been shown to provide equivalent results to standard methods when testing food and environmental samples, however, no data is available for the performance of the system with gelatin.

Purpose: To evaluate the 3M Molecular Detection Assay – Salmonella and the new 3M Molecular Detection Assay 2 - Salmonella for screening animal based powdered gelatin and comparing the results to those obtained using the Australian standard method (ISO 6579)

Methods: The 3M Molecular Detection Assay methods required the enrichment of samples in Buffered Peptone Water for 18-24 h then processing and analysis as per the manufacturer’s instructions. The Australian standard method requires overnight enrichment in Buffered Peptone Water then subculturing into MKTTn and RVS for selective enrichment. After 24 hours, the selective enrichments are then plated onto XLD agar plus an alternative. The samples analyzed in the study were as provided by the manufacturer, and then a portion was artificially inoculated with 3 different Salmonella serovars at low levels to provide positive results.

Results: Of the 45 samples tested for Salmonella using each system, 36 were positive by each 3M Molecular Detection Assay and the Australian standard method while 9 were negative in each method. The results showed 100% agreement between the three methods under the test conditions used.

Significance: The 3M Molecular Detection Assay - Salmonella and the 3M Molecular Detection Assay 2 - Salmonella both provide presumptive positive results for the presence of Salmonella in gelatin, within 24 hours, allowing for more timely reporting of results and release of product without compromising accuracy.