Validation of the Applied Food Diagnostics, Inc. Molecular Environmental Monitoring Program (MEMP) Listeria Assay for Detection of Listeria Spp. in Environmental Surface Samples: AOAC Performance Tested MethodSM 052003.

Abstract

The Molecular Environmental Monitoring Program (MEMP) Listeria Assay is a quick, reliable method for detecting Listeria species in environmental samples. The assay incorporates a real-time PCR approach to identifying Listeria cells expressed from the swab sample. The assay does not require an enrichment step, leading to much faster time to a negative result. This report details the method validation study to validate the MEMP using environmental surface swabs for stainless steel, plastic, rubber, ceramic tile, and sealed concrete. Matrix studies, inclusivity/exclusivity, product consistency and stability, and robustness testing were conducted to assess the method's performance. In the matrix studies, this method was compared to the US Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Chapter 10 for environmental surface sponges and swabs. Inclusivity and exclusivity testing showed that the MEMP Listeria Assay was able to detect all 75 Listeria strains tested while excluding the 30 non-Listeria species. There were no statistically significant differences found between the candidate and reference methods. Small variations in critical test parameters (volume of extraction reagent and volume of extracted DNA sample) did not adversely affect the assay's performance, and stability testing indicated consistent results for at least 1 year. The data presented in this report show that the candidate method performed as well as the reference method and can therefore be used in place of the reference method for detecting Listeria species. The MEMP Listeria Assay requires no enrichment for detecting Listeria on environmental surfaces.