Analysis of Alternative Methods of Environmental Monitoring for Listeria in Food Production Facilities

Validated alternative test methodologies may be used in place of culture-based methods recommended for environmental monitoring programs (EMPs) for Listeria in food production facilities. In order to help guide decisions on which testing method to use to simplify Listeria EMP implementation in food production facilities, alternative methods were compared to the culture-based method in actual EMPs for Listeria. Seventy-two samples collected from two facilities of souzai production businesses that use meat and meat products as ingredients, one facility of processed meat product production business, and one facility of processed meat product and souzai production business were applied to EMPs for Listeria using the culture-based method, 3M^TM Molecular Detection System (MDS), and InSite L. mono Glo (InSite). The kappa coefficient in MDS was 0.65 for Listeria monocytogenes and 0.74 for Listeria spp., both of which were deemed substantial compared with the culture-based method. The kappa coefficient in InSite was -0.01 for L. monocytogenes and 0.50 for Listeria spp., which indicated poor and moderate reproducibility, respectively. When the medium of InSite was smeared on agar medium, 7 of the 19 samples tested positive only for Listeria spp. (negative for L. monocytogenes) but L. monocytogenes was cultured, indicating that the sensitivity of detecting L. monocytogenes via fluorescence may be low. MDS was considered a useful alternative for both L. monocytogenes and Listeria spp. as targets, and InSite was not possible as a substitute for detecting L. monocytogenes; however, it is considered a helpful alternative method for detecting Listeria spp. EMPs for Listeria often target Listeria spp. as an indicator of L. monocytogenes. The alternative methods studied in this study are rapid, simple, and useful in EMPs for Listeria. However, the data in this study were a comparatively small sample set and impacted by variability, so more robust comparisons are desirable in the future.