In the quest for reliable tools to explore the virulence potential of Listeria monocytogenes clonal complexes

Introduction and objective: Listeria monocytogenes is a foodborne pathogen that causes human listeriosis. This pathogen is characterized by an intra-species heterogeneity so its strains can be grouped into clonal complexes (CCs) that are defined either as hypervirulent – mainly associated with clinical cases or hypovirulent – associated with food or food processing environments and with infections in susceptible groups [1]. The impact of L. monocytogenes extends beyond health concerns to economic implications since detection of contaminated food results in production interruptions and product recalls. Considering the persistence of L. monocytogenes in the food industry, there is an urgent need to define reliable biomarkers and to determine whether CC characterization is robust enough to discriminate high-risk strains. Listeria monocytogenes has a typical β-hemolytic profile, which is outlined by crucial virulence factors (hly and prfA genes), however, some strains exhibiting non- hemolytic or attenuated hemolysis have been reported [2]. The aim of this work was to investigate if these phenotypes could be associated with hypovirulent CCs.