A Comparative Evaluation of the 3M™ Molecular Detection Assay Listeria for the Detection of Listeria species in Foods

Introduction: Listeria is frequently associated with food and environmental surface contamination and is a significant food safety concern. The 3M^™ Molecular Detection Assay Listeria is designed for rapid and specific detection of these adulterants in food samples after only 26 hours incubation.  Using the 3M^™Modified Listeria Recovery Broth (mLRB) as the enrichment medium, the assay uses a combination of isothermal amplification of unique DNA target sequences and bioluminescence to analyze and detect the amplified sequences.

Purpose: The purpose of the study was to evaluate the ability of the MDA Listeria to detect Listeria species in a variety of foods in comparison to the FDA BAM Chapter 10, AOAC 993.12 and USDA/FSIS MLG 8.07 methods.

Methods: This new method and comparative reference methods were analyzed by testing 4 food matrices at 3 separate inoculum levels; 20 replicates were inoculated at a low inoculum level of 0.2-2.0 CFU/test portion, 5 replicates were inoculated at a high inoculum level of 2-5 CFU/test portion, and 5 replicates at an uninoculated control level of 0 CFU/test portion. The test portions were analyzed by the new method after 26 hours of incubation.

Results: Statistical analysis was conducted using the Probability of Detection (POD) statistical model and there were no significant differences between the candidate method and the reference method for each of the four matrices tested at the low inoculum level after 26 hours incubation.

Significance: The Molecular Detection Assay Listeria offers the capability of detecting Listeria species in foods after only 26 hours of incubation, thereby reducing the amount of time until presumptive detection in comparison to traditional reference methods.