The arsenal of virulence factors deployed by Listeria monocytogenes to promote its cell infection cycle

Listeria monocytogenes is an intracellular Gram-positive pathogen and the etiological agent of listeriosis, a human foodborne disease potentially fatal for certain risk groups. The virulence of L. monocytogenes is supported by a highly complex and coordinated intracellular life cycle that comprises several crucial steps: host cell adhesion and invasion, intracellular multiplication and motility, and intercellular spread. The completion of each stage is dependent on the orchestrated activity of specialized bacterial factors, in turn tightly controlled by a specific set of regulators. Some virulence factors and modulators also assume an important role in bacterial resistance and evasion to host defense mechanisms. In the last years, the advent of genomics promoted an increasingly prolific identification and functional characterization of new Listeria virulence factors. In this review, we summarize the current knowledge on nearly 50 molecules deployed by L. monocytogenes to promote its cell infection cycle.