How the bacterium Listeria monocytogenes survives in the environment and interacts with mammalian cells during infection has been, during the last three decades the object of intense investigation. This bacterium is still responsible for severe food borne infections leading to gastroenteritis, meningitis and abortions, with a mortality rate of 30%. The recent epidemics in South Africa has demonstrated that epidemics can still occur and lead to an important number of deaths. The capacity of Listeria to produce an infection is due to its ability to cross three tight host body barriers : the intestinal barrier, the blood brain barrier,and the placental barrier. An arsenal of « virulence factors » allows Listeria to survive and persist in the intestinal lumen, to enter into cells and disseminate in the various tissues that it infects, exploiting cellular signaling pathways and components to its own profit in order to escape host defence mechanism. To identify and characterize these factors, we have used a combination of targeted and genome wide approaches coupled to cutting edge technologies e.g. fluorescence microscopy, live cell imaging and mass spectrometry. The talk will give an overview of both well established concepts and recent data, e.g. presence of bacteriocins that contribute to the interaction of Listeria with the gut microbiome.