Distribution of Internalin Gene Profiles of Listeria monocytogenesIsolates from Different Sources Associated with Phylogenetic Lineages

Listeria monocytogenesis a human foodborne pathogen with a broad range of hosts. While the L. monocytogenesgenome encodes a number of internalins, which are leucine-rich repeat bacterial surface proteins with putative or confirmed roles in host cell attachment and invasion, the specific function of many internalins remains unclear. The distribution of 7 internalin genes (inlC, inlC2, inlD, inlE, inlF, inlG, and inlH) in 120 L. monocytogenesisolates from humans, foods, and animals was investigated to determine if the distribution of these proteins differed with respect to source or phylogenetic lineage. Isolates were classified into 6 different profiles based on internalin gene presence or absence, and a phylogeny based on one stress response (sigB) and two housekeeping (gapand prs) genes was used to correlate these profiles with L. monocytogenesphylogenetic lineages. All 69 isolates classified into L. monocytogeneslineage I, which is overrepresented among human disease cases, had the same internalin profile (presence of inlCand the inlC2DEoperon). Lineage II (48 isolates), which is common among food and environmental sources, represented 4 internalin gene profiles, with most isolates carrying inlGand inlFin addition to inlCand inlC2DE. Our data indicate that L. monocytogenesisolates show diverse and distinct patterns of internalin gene presenceabsence and L. monocytogenesinternalin profiles are associated with phylogenetic lineages.