Performance of the 3M™ Molecular Detection Assay Listeria monocytogenes as Compared to the Canadian Reference Method MFHPB-30

Introduction: In recent years, 132 cases of Listeriosis on average were reported annually in Canada. Listeria monocytogenes is usually associated with environmental contamination within food production facilities and is a significant food safety concern and cost. The 3M™ Molecular Detection Assay Listeria monocytogenes is used with the 3M™ Molecular Detection System for the rapid and specific detection of Listeria monocytogenes in food and environmental samples. The 3M™ Molecular Detection Assays employs isothermal amplification of nucleic acid sequences to achieve specificity, efficiency and rapidity, utilizing bioluminescence to detect the amplification of the target.

Purpose: The objective of this study was to evaluate the performance of the 3M™ Molecular Detection Assay Listeria monocytogenes against the Compendium of Analytical Methods MFHPB-30 in a variety of food matrices for the inclusion in the Compendium of Analytical Methods.

Methods: The 3M™ method and comparative reference method (MFHPB-30) were analyzed by testing 5 food categories with 3 matrices per category (RTE Meat and Poultry, Fish and Seafood, Dairy, Fruit and Vegetable Products, Raw Poultry). Three separate inoculum levels were used; 20 samples at 1 - 5 CFU/25 g, 20 samples at approximately 1 log CFU/25 g higher, and 5 negative controls.

Results: Statistical analysis was conducted using the Probability of Detection statistical mode. This showed a relative sensitivity of 99.5%, relative specificity of 98.2%, false positive rate of 1.8%, and false negative rate of 0.5% for a total test efficacy of 99.0%. This exceeded the criteria outlined by the Health Canada MMC. Level of Detection results showed a range of 0.5 - 6.375 MPN/25 g. 

Significance: The 3M™ Molecular Detection Assay Listeria monocytogenes showed excellent performance and exceeded the MMC requirements. This new method offers the capability of detecting Listeria monocytogenes in foods after only 24 - 48 hours of incubation, thereby significantly reducing presumptive reporting times over the reference method.