Rapid detection and differentiation of Listeria monocytogenes and Listeria species in deli meats by a new multiplex PCR method

Abstract

Listeria monocytogenes is an important foodborne pathogen. To effectively control this pathogen, it is necessary to have a method that can detect and differentiate L. monocytogenes from other Listeria species in food, environmental, and clinical samples. A new multiplex PCR method using new primers targeting the iap gene was developed to detect and differentiate L. monocytogenes and other Listeria species, and the method was applied to examine deli meat samples. Sixteen Listeria strains (8 L. monocytogenes, 2 Listeria innocua, 1 Listeria seeligeri, 3 Listeria welshimeri, 1 Listeria ivanovii, and 1 Listeria grayi) from the American Type Culture Collection were tested using the new PCR method in comparison to 16S rRNA sequencing assay and a previously described PCR method based on the detection of iap gene with other primers. The new PCR method was able to differentiate L. monocytogenes from the other Listeria species, while the 16S rRNA sequencing assay could not distinguish L. welshimeri from L. monocytogenes and the previously published multiplex PCR assay was not able to distinguish L. monocytogenes from L. innocua or L. ivanovii. Furthermore, 150 deli meat samples were analyzed by the newly developed multiplex PCR in comparison to ISO11290-1 method and 16S rRNA sequencing assay to detect L. monocytogenes and differentiate it from the other 5 species of Listeria. The developed PCR provided the same results as the ISO method. Out of 150 samples, 16 (10.7%) samples and 5 (3.3%) samples were tested positive and confirmed for Listeria spp. and L. monocytogenes, respectively. The multiplex PCR method is capable of discriminating between L. monocytogenes and other Listeria species. The method is simple and specific when combined with simplified enrichment procedures.