Listeria monocytogenes: Host-pathogen interactions and innate immune response.

Listeria monocytogenes is primarily a saprophytic bacterium, but it can transition into a pathogenic form when ingested by humans, vertebrates, or invertebrates, thereby initiating infection and proliferating within the host. This bacterium serves as a model for studying the molecular and cellular mechanisms by which environmental microorganisms adapt to mammalian and other host systems, thereby promoting the successful colonization and survival of these microorganisms. Environmental contamination is a significant factor in the transmission of listeriosis and other foodborne diseases. This review provides a comprehensive examination of the microbiological characteristics of L. monocytogenes. It systematically evaluates host-pathogen interactions, focusing on a range of clinically relevant isolates and their pathogenic mechanisms. Furthermore, it evaluates in vitro models employed to investigate the virulence factors of the pathogen while also considering the role of animal models, including Drosophila melanogaster and other insect species, in elucidating infection dynamics. In addition, it discusses the host's innate immune response, specifically highlighting the molecular and cellular pathways activated upon infection, thereby providing a comprehensive understanding of the pathogen's interactions with the host's immune system.