Making Sense of the Biodiversity and Virulence of Listeria monocytogenes

Listeria monocytogenes is a foodborne opportunistic bacterial pathogen. Classical genetic approaches in reference strains allowed identification of core virulence genes. Investigation of the species diversity of L. monocytogenes allowed uncovering of hypo- and hypervirulent strains and new virulence genes. Hypervirulent strains are host associated, whereas hypovirulent strains are associated with food-processing environments. Accumulation of loss-of-function mutations in virulence pathways leads to niche restriction and obligate saprophytism. Listeria monocytogenes is a foodborne pathogen responsible for listeriosis, an infection that can manifest in humans as bacteremia, meningoencephalitis in immunocompromised patients and the elderly, and fetal-placental infection in pregnant women. Reference strains from this facultative intracellular bacterium have been instrumental in the investigation of basic mechanisms in microbiology, immunology, and cell biology. The integration of bacterial population genomics with environmental, epidemiological, and clinical data allowed the uncovering of new factors involved in the virulence of L. monocytogenes and its adaptation to different environments. This review illustrates how these investigations have led to a better understanding of the bacterium’s virulence and the driving forces that shaped it. Listeria monocytogenes is a foodborne pathogen responsible for listeriosis, an infection that can manifest in humans as bacteremia, meningoencephalitis in immunocompromised patients and the elderly, and fetal-placental infection in pregnant women. Reference strains from this facultative intracellular bacterium have been instrumental in the investigation of basic mechanisms in microbiology, immunology, and cell biology. The integration of bacterial population genomics with environmental, epidemiological, and clinical data allowed the uncovering of new factors involved in the virulence of L. monocytogenes and its adaptation to different environments. This review illustrates how these investigations have led to a better understanding of the bacterium’s virulence and the driving forces that shaped it.