An Alternative Tool for Monitoring the Presence of Listeria spp. in the Industrial Environment

Introduction: Environmental monitoring is recognized as an important strategy to control Listeria spp. in food processing facilities. In addition to contamination at food-contact areas, the target pathogen can be found in many non-processing areas increasing the probability of the pathogen being transferred to the food products.

Purpose: The main goal was to evaluate FoodChek^TM Listeria spp., an immunomagnetic lateral flow assay, as a tool for monitoring Listeria spp. in industrial environment.

Methods: Non-food contact surfaces (180) were artificially contaminated with Listeria spp., dried overnight and swabbed. Half of the samples were tested by the new assay while the remaining were tested by the USDA-FSIS cultural method. The difference between both methods was evaluated by χ²-analysis.

The efficacy of the assay was evaluated using 48 sponge samples that were collected from non-food contact surfaces at the deli meat-slicing department. The sponges were then used in the laboratory, for sampling surfaces artificially contaminated with Listeria. All results were confirmed using the reference culture method.     

Results: Single-step enrichment with ACTERO™ Listeria medium at 32°C for 24–28 hours was determined as the most efficient for following detection of Listeria spp. by the assay. For ceramic and sealed concrete surfaces, no significant differences were found in the number of positive outcomes obtained by the assay when compared to the double-step enrichment reference method MLG 8.08. However, for rubber surfaces, the assay showed significantly higher performance (χ² = 5.6) as compared to MLG 8.08. Neither false negatives nor false positive outcomes were documented.

All sponge samples collected at the deli meat department were correctly detected using the assay. The results were confirmed by the transfer to double enrichment step. There were no cases of contamination of the samples with wild Listeria spp.       

Significance: The new assay presents accurate, rapid and simple alternative to standard culture methods for Listeria detection in industrial environment.