Rapid Detection of Listeria spp. from Environmental Samples Using a New Immunomagnetic Assay

Introduction: Ubiquitous Listeria species are the microbial targets of most Food Quality Management Programs, particularly those due to L. monocytogenes. This species is among the most important causes of death from foodborne infections in all industrialized countries. The preventive activity requires the rapid detection of this pathogen or its indicator to guarantee the production of safe food.

Purpose: The aim of this study was to validate FoodChek^TMListeria spp. assay and to compare its efficacy to the reference method MLG 8.08.

Methods: The performance of the new immunomagnetic lateral flow assay was evaluated using ACTERO™ Listeria Enrichment Media allowing a 24-hour single enrichment step, and following the Guidelines of the AOAC for the Performance Tested Methods^SM. The evaluation included a matrix study of Listeria spp. detection from environmental samples. There were 121 environmental samples from stainless steel and plastic food contact surfaces tested by the new assay and these were compared with 52 samples analyzed using the USDA-FSIS reference cultural method. The Chi square analysis was performed to evaluate the difference between both methods.

Results: The Listeria spp. assay detected the five species most frequently isolated from food (L. monocytogenes, L. ivanovii, L. innocua, L. seeligeri, L. welchimeri). None of the 30 non-Listeria strains tested reported a positive signal.

Listeria spp. was more frequently detected from plastic samples by the new assay (χ² = 4.4; P < 0.05) as compared to MLG 8.08. However, no differences (χ² = 2.0) were observed when stainless steel samples had been analyzed. The original assay allows for the detection of Listeria spp. from environmental surfaces in less than 25 h, including enrichment and detection steps.

Significance: The new immunomagnetic Listeria spp. assay provides food processors with a rapid and reliable tool to monitor and to control Listeria spp.