Evaluation of Environmental Sampling Methods and Rapid Detection Assays for Recovery and Identification of Listeriaspp. from Meat Processing Facilities

Studies that isolated Listeriaspp. from the environment of two meat processing facilities were conducted. Samples were collected in the processing environment of the facilities with three different sampling methods (cotton swab, sterile sponge, and composite-ply tissues) to evaluate their ability to recover Listeriaspp. A total of 240 samples for each sampling method were collected and tested. The cotton swab method of sampling was significantly (P< 0.01) less efficient in recovery of Listeriaspp. than the sterile-sponge and composite-ply tissue methods, which were similar (P> 0.05) in their ability to recover Listeriaspp. The specificity and sensitivity of four detection methods (conventional culture, Petrifilm Environmental ListeriaPlates [ELP], lateral-flow immunoprecipitation [LFI], and automated PCR) were evaluated for identification of Listeriaspp. Facilities were visited until a minimum of 100 positive and 100 negative samples per detection method were collected. The LFI and PCR methods were highly sensitive (95.5 and 99.1%, respectively) and specific (100%) relative to the culture method. The ELP method was significantly less efficient (P< 0.01) than LFI and PCR in detection of Listeriaspp., with lower sensitivity (50.6%) and specificity (91.5%). Kappa values indicated excellent agreement of the LFI and PCR assays and moderate agreement of the ELP method to the culture method. Overall, ELP was easy to use but less efficient in detection of Listeriaspp. from environmental samples, while the LFI and PCR methods were found to be excellent alternatives to culture, considering performance and time and labor inputs.