A genome-wide screen inex vivogallbladders identifiesListeria monocytogenesfactors required for virulencein vivo

Abstract

ABSTRACTListeria monocytogenesis a Gram-positive pathogen that causes the severe foodborne disease listeriosis. Following oral infection of the host,L. monocytogenesdisseminates from the gastrointestinal tract to peripheral organs, including the gallbladder, where it replicates to high densities. The gallbladder then becomes the primary bacterial reservoir and source of fecally excreted bacteria. Despite its importance in pathogenesis, little is known about howL. monocytogenessurvives and replicates in the gallbladder. In this study, we assessed theL. monocytogenesgenes required for growth and survival inex vivonon-human primate gallbladders using a transposon sequencing approach. The screen identified 43 genes required for replication in the gallbladder, some of which were known to be important for virulence, and others had not been previously studied in the context of infection. We evaluated the roles of 19 genes identified in our screen bothin vitroandin vivo, and demonstrate that most were required for replication in bilein vitro, for intracellular infection of murine cells in tissue culture, and for virulence in an oral murine model of listeriosis. Interestingly, strains lacking the mannose phosphoenolpyruvate-dependent phosphotransferase system (PTS) permeases Mpt and Mpo exhibited no defects in intracellular growth or intercellular spread but were significantly attenuated during murine infection. While the roles of PTS systemsin vivowere not previously appreciated, these results suggest that PTS permeases are necessary for extracellular replication during infection. Overall, this study demonstrates thatL. monocytogenesgenes required for replication in the gallbladder also play broader roles in disease.