Recent data from our research group showed that null mutant strains of Salmonella enterica to genes encoding Naps (nucleoid-associated proteins) were attenuated for virulence and capable of inducing, in variable degrees, protection in the murine infection model. These results suggested an important role of different Naps in the bacterial virulence. During the development of our Postdoc project (Fapesp 2013/26073-4) we studied the biological role of the Nap IHF (integration host factor) for Salmonella Enteritidis (SE) in the chicken infection model. Our main intention was to assess the potential of SE single mutant strains ihfA and ihfB, and SE double mutant strain ihfAihfB to act as vaccine strains for poultry, in view of the superiority of live vaccines in comparison to bacterins.Only, SEihfA fulfilled the requirements of attenuation, and subsequent assays of vaccine potential has been carried out using this strain. Despite of this, a remarkable regulation of ihf genes in SE could be verified in chickens. According to our observations, ihfA and ihfB deletions were detrimental to SE systemic spread, probably by some effect of deletions in the bacteria access to avian reticuloendothelial system or survival into phagocytic cells. On the other hand, in the absence of ihfB or both ihfA and ihfB genes a beneficial effect in the ability of caecal colonization was observed. Therefore, we found that ihf genes might be playing divergent roles in set of genes responsible for intestinal colonization and systemic infection.This project aims to study in vitro the infection of avian phagocytic cell lines and chicken primary intestinal epithelial cells in order to corroborate our in vivo observations and increase information about mechanisms underlying intestinal colonization and systemic dissemination of SE.
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