Performance of a Molecular Detection System for the Detection of Salmonella and Escherichia coli O157 in Food and Carcass Samples

Introduction: Testing for Salmonella and E. coli O157:H7 is a critical component of food safety programs as contamination by these pathogens can result in significant adverse health conditions and economic loss. The 3M™ Molecular Detection Assay Salmonella and the 3M™ Molecular Detection Assay E. coli O157 (including H7) were developed for the rapid and specific detection of these organisms after enrichment. The assay uses a combination of isothermal amplification of unique DNA target sequences and bioluminescence to detect the amplified sequences.

Purpose: To evaluate the performance of detection methods using a variety of foods and poultry and beef carcasses.

Methods: Salmonella and E. coli O157 were used to artificially contaminate > 95 food samples with 5-13 CFU of target pathogen per sample size. Additional > 140 samples beef and poultry carcasses were also tested. Two test periods were conducted: 1) one sample was enriched blank and one was artificially contaminated with ~10 CFU of the target organism and 2) samples were enriched blank to evaluate for native contamination. Enrichments were tested using detection molecular assays and selective and differential agar &/or quantitative PCR.

Results: Compared to agar or qPCR, accuracy, specificity and sensitivity were: 97.6%, 100%, and 93.9% for the molecular detection assay Salmonella, and 95%, 100%, and 92% for the 3M Molecular Detection Assay E. coli O157 (including H7).

Significance: The methods demonstrated comparable results to the other methods for the rapid, automated detection of these organisms.