Multiple invasion mechanisms and different intracellular Behaviors: a new vision of Salmonella-host cell interaction

Salmonella is a facultative intracellular bacterium found within a variety of phagocytic and nonphagocytic cells in vitro and in vivo. For decades, it has been accepted that Salmonella can enter cells only through a Trigger mechanism mediated by a type three secretion system, called T3SS-1. However, recent researches have shown that this bacterium can use other invasion pathways mediating either Trigger or Zipper entry processes. Following eukaryotic cell invasion, Salmonella has to ensure its survival and proliferation within host cells. To do so, this bacterium resides either within a membrane-bound vacuole or freely within host cell cytosol. It is not clear why Salmonella has developed these alternate mechanisms for cell invasion and proliferation, but this provides a new insight into the mechanisms leading to Salmonella-induced diseases. Thus, the aim of this review is to show the evolution of Salmonella-host cell interaction paradigms by summarizing the different strategies used by Salmonella serotypes to invade and proliferate into eukaryotic cells.