Evaluation of 3M™ loop-mediated isothermal amplification-based kit and 3M™ ready-to-use plating system for detection of Listeria in naturally contaminated leafy vegetables, chicken, and their related processing environments

The effectiveness of two different rapid methods involving the 3M™ molecular detection assay Listeria and the 3M™ Petrifilm environmental Listeria Plate were evaluated for the rapid detection of Listeria from naturally contaminated vegetables and chicken-processing environments against the standard culture-based method. A total of 178 samples were examined for the presence of Listeria. A total of 47/178 (26.4%) by standard ISO culture-based method (EN ISO 11290-1), 42/178 (23.6%) by 3M™ MDA Listeria and 40/178 (22.5%) by 3M™ Petrifilm EL Plate showed positive results, respectively. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for 3M™ MDA Listeria and 3M™ Petrifilm EL Plate were 97.2, 89.4, 99.3, 97.7, 96.4% and 96.1, 85.1, 100.0, 100.0, 94.9%, respectively. Based on the Cohen's Kappa value, there was a complete and robust concordance between 3M™ MDA Listeria (0.911) and 3M™ Petrifilm EL Plates (0.894) as compared to the standard culture-based method.