Multiplex PCR assay simplifies serotyping and sequence typing of Listeria monocytogenes associated with human outbreaks

Listeria monocytogenes serotypes 1/2a and 4b are responsible for the majority of cases of human listeriosis worldwide. In this study, a multiplex PCR assay was developed to allow rapid identification and easily interpretable differentiation of serotypes 1/2a and 4b from other serotypes of L. monocytogenes by simultaneously targeting two virulence genes (inlB and inlC) and two serotype-specific genes (ORF2372 and lmo0171). A subsequent gel extraction and sequence typing analysis of the highly polymorphic intragenic regions in inlB and inlC simplified a previously developed multi-virulence-locus sequence typing scheme and provided discriminatory power for subtyping L. monocytogenes similar to pulsed-field gel electrophoresis analysis.