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The prominence of S. Heidelberg and S. Kentucky among poult<P>ry, and their increased association with human disease, raises concerns that these are the next emerging poultry-associated Salmonella serovars of human health importance. Our long-term goal is to understand changes in the Salmonella populations associated with food production animals as a result of changes in selection pressure, management practices, and intervention strategies along the "farm-to-table" food supply chain.<P> The central hypothesis of the proposed research is that S. Kentucky and/or S. Heidelberg are the next emergent Salmonella serovars of poultry and human health importance.<P> The overall objectives of this work are to determine the following: 1) why S. Kentucky and S. Heidelberg are the prominent Salmonella serovars in poultry; 2) if these serovars present a human health risk; 3) how these serovars can be eliminated from poultry.
Non-Technical Summary: Certain Salmonella serovars have recently emerged as apparently dominant in poultry, without reasonable explanation of the mechanisms by which these strains are able to persist. The subset of in vivo induced genes identified here will provide specific targets on which we can focus in future work, aimed at understanding what makes a Salmonella strain an efficient colonizer of poultry. Also, the IVET approach could be extended to study other aspects of Salmonella persistence in poultry, such as survival in litter or retail meat products. This work will begin to address the objective pertaining to "why" S. Heidelberg and S. Kentucky are so successful in broilers and commercial broiler facilities. This will facilitate future studies assessing the risk of this phenomenon to human health, and the means by which these serovars can be reduced or eliminated from poultry. <P> Approach: We will focus on Salmonella chicken colonization, since these serovars have been shown to colonize broiler chickens more efficiently than other Salmonella serovars (unpublished data). Here, we will use in vitro expression technology (IVET) as a positive selection tool to identify genes that are induced during chicken colonization. We will follow modified procedures for use of a nonchromosomal integration system with a low copy number plasmid for large-scale screening of promoter traps. We will also perform a comprehensive in silico genomic comparison of sequenced Salmonella strains to determine "avian-specific" subset of genes potentially important for persistence in poultry or the poultry farm environment. From this work, a subset of S. Heidelberg and S. Kentucky genes induced exclusively during chicken colonization and "avian-specific" Salmonella genes/loci will be identified and used for subsequent characterization in future proposals. In itself, this work will provide valuable data pertaining to the propensity of certain Salmonella serovars to persist among poultry and poultry farms.