Abstract

Pathogenicity island excision is a phenomenon that has been described in several serovars of Salmonella enterica subspecies enterica. ROD21 is an excisable Pathogenicity Island found in the chromosome of S. Enteriditis that harbors several genes encoding associated virulence proteins. Our previous studies have shown that ROD21 excision may play a role in the ability of S. Enteritidis to cause systemic infection in the mouse because strains unable to excise ROD21 show reduced ability to colonize liver and spleen. In this work, we determined the dynamic of ROD21 excision in vivo across the stages of the infective cycle performed by S. Enteritidis in mice. After different times post-infection, bacterial load and excision frequency were determined in the gut and internal organs. We observed that S. Enteritidis colonize the gut during the first 24h, could be detected at 6h on mesenteric lymph nodes (mLN) and appear on internal organs, such as spleen and liver, after 48h. We observed that the excision of ROD21 is a dynamic process across the infective cycle in the evaluated organs. Interestingly, on mLN, the bacterial population had the high rates of ROD21 excision of all evaluated organs, during the first 96 h post-infection but contrary to that, excision remains lower or undetectable on liver and spleen at this time, increasing drastically after 14 h post infection. In contrast, a mutant strain, unable to excise ROD21, has a severe defect to colonize deeps organs after 96 hours postinfection.