Performance of a New Molecular Platform for the Detection of Listeria monocytogenes in Thai Seafood Matrices

Introduction: Listeria monocytogenes is a widely recognized hazard in the food industry, associated with many types of food, (including seafood). Thailand’s exports of fresh, chilled and frozen seafood products stand at around 570,000 metric tons per annum with production centralized around the Samutsakorn and Samutsongkhram provinces. Pre-export certification and inspection is provided by the Samutsakorn Fish Inspection and Research Center (SFIRC) [part of the Department of Fisheries], however, current test methods for pathogens are perceived as complicated and lengthy. For the expansion of the Thai seafood export industry, SFIRC has prioritized the qualification of molecular methods for rapid Listeria monocytogenes detection.

Purpose: To evaluate the performance of a molecular method for the detection of Listeria monocytogenes through comparison with a cultural method for Thai seafood matrices, including [1] Raw Fish, [2] Raw Shrimp, & [3] Raw Octopus.

Methods: A total of 120 samples were analyzed; 60 samples were artificially contaminated with a cocktail of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli; 60 samples were tested with natural contamination. After enrichment in Demi Fraser Broth Base and Fraser Broth Base, the samples were analyzed by 3M™ Molecular Detection Assay Listeria monocytogenes, and a cultural method following the US FDA Bacteriological Analytical Manual (BAM). Presumptive positive molecular results were culturally and biochemically confirmed following BAM protocols.

Results: For the 120 samples tested, the molecular method showed 100% sensitivity, 100% accuracy, 100% specificity and no significant difference from the cultural method using the chi-square statistic.

Significance: Testing artificially and naturally contaminated seafood matrices from Thailand, the 3M Molecular Detection Assay Listeria monocytogenes was found to be sensitive and accurate. Other benefits were noted — including faster time-to-results — that demonstrate the significance of this evaluation for the Thai seafood export industry.