Intestinal Colonization of Mice and Chickens by Salmonella Enteritidis

NON-TECHNICAL SUMMARY: Salmonella enteritidis causes a large number of cases of human infection in the United States. The majority of human infections of S. enteritidis are caused by contaminated chicken products (especially the chicken eggs), and chickens are believed to be infected by rodents infesting poultry farms. S. enteritidis often does not cause symptoms in infected chickens or mice. Instead it infects the intestinal track and silently spreads through fecal shedding. We hypothesize that S. enteritidis has a specific set of genetic factors responsible for its infection of the intestinal tract of hosts. We will identify the factors by a genetic screening to select mutants that are unable to infect the intestinal tract in mice and chickens. Once these bacterial factors are identified, we will study the functions of the factors and analyze why they are important for intestinal infection. Through the experiments in this proposal, we hope to improve our understanding of how food-borne pathogens such as Salmonella infect the host intestinal tract. The bacterial factors and mechanisms of Salmonella infection identified in this study can be used as targets to reduce the spread of Salmonella in farm animals and to the human population.

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APPROACH: Using infections of mouse and chicken as the experimental systems, the proposed study is to identify the bacterial genes required for S. enteritidis to colonize the intestinal tissues by a signature-tagged mutagenesis coupled with negative selection approach. Bacterial mutants that are defective in colonizing Peyers patches and ceca of mice and chickens will be isolated, the genes that are mutated will be identified, and the pathogenicity of the mutants will be investigated.