Insight into the genetic diversity, resistance, and virulence of Listeria from the marine environment: reveal the risk of hypervirulent isolates

Listeria monocytogenes is a major human foodborne pathogen and a ubiquitous environmental saprophyte. In this study, we investigated the prevalence and characteristics of Listeria spp. from beach sand in the coastal environment. Three different Listeria spp., Listeria monocytogenes (n=16), Listeria fleishmanii (n=7), and Listeria aquatica (n=3) were isolated from 769 beach sand samples and demonstrated diverse biofilm forming capacity. The L. monocytogenes isolates belonged to four distinct sequence types (ST87, ST121, ST35, and ST85) and contained the majority of virulence genes, some isolates were hypervirulent clones or had close phylogenetic relatedness with clinical cases. The ST87 isolates showed higher ability of biofilm formation in seawater than other STs strains. As a reservoir of microbes from marine environments and human/animal excrement, coastal sand would play an important role in the spread of L. monocytogenes and is an environmental risk for human listeriosis.