A large panel of chicken cells are invaded in vivo by Salmonella Typhimurium even when depleted of all known invasion factors
Poultry are the main source of human infection by Salmonella. As infected poultry are asymptomatic, the identification of infected poultry farms is difficult. Controlling animal infections is thus of primary importance. As cell tropism is known to govern disease, our aim was therefore to identify the infected host-cell types in chicks and the role of the three known invasion factors in this process (T3SS-1, Rck and PagN). Chicks were inoculated with wild-type or isogenic fluorescent Salmonella Typhimurium mutants via the intraperitoneal route. Our results show that liver, spleen, gall bladder and aortic vessels could be foci of infection and that phagocytic and non-phagocytic cells, including immune, epithelial and endothelial cells, are invaded in vivo in each organ. Moreover, a mutant defective for the T3SS-1, Rck and PagN remained able to colonize organs as the wild-type strain and invaded non-phagocytic cells in each organ studied. As the infection of gall bladder was not really described in chicks, invasion of gall bladder cells was confirmed by immunohistochemistry and infection was shown to last several weeks after inoculation of chicks. All together, these findings provide new insights into the dynamics of Salmonella spread in vivo in chicks at the organ and cellular levels.