Identification of high-risk Listeria monocytogenes serotypes in lineage I (serotype 1/2a, 1/2c, 3a and 3c) using multiplex PCR

AimsUsing molecular subtyping techniques, Listeria monocytogenes is divided into three major phylogenetic lineages, and a multiplex PCR method can differentiate five L.monocytogenes subgroups: 1/2a-3a, 1/2c-3c, 1/2b-3b-7, 4b-4d-4e and 4a-4c. In this study, we conducted genome comparisons and evaluated serotype-associated genes for their utility as a multiplex PCR-based method for distinguishing high-risk serotypes 1/2a and 1/2c in lineage I from low-risk serotypes 3a and 3c. Methods and ResultsPrimer sets were developed that are specific for serotype 1/2c (LMOSLCC2372_0308) and serotype 3a (LMLG_0742). These primers were then tested in a multiplex format with primers specific for serotype 1/2a (flaA) to separate serotypes 1/2a, 1/2c, 3a and 3c using 25 strains of lineage I L.monocytogenes. ConclusionsHere, for the first time, we report primers specific for L.monocytogenes serotype 1/2c and serotype 3a, and we demonstrate a multiplex PCR method for separating the four serotypes of lineage I L.monocytogenes. Significance and Impact of the StudyThe described multiplex PCR assay consistently showed successful separation of 1/2a and 1/2c strains from 3a and 3c strains. PCR is routinely performed in many diagnostic and epidemiologic investigations for L.monocytogenes, and these primers should increase the feasibility and accessibility of L.monocytogenes serotyping.