rpoS -Regulated Core Genes Involved in the Competitive Fitness of Salmonella enterica Serovar Kentucky in the Intestines of Chickens

Salmonella enterica serovar Kentucky has become the most frequently isolated serovar from poultry in the United States over the past decade. Despite its prevalence in poultry, it causes few human illnesses in the United States. The dominance ofS . Kentucky in poultry does not appear to be due to single introduction of a clonal strain, and its reduced virulence appears to correlate with the absence of virulence genesgrvA ,sseI ,sopE , andsodC1. S . Kentucky's prevalence in poultry is possibly attributable to its metabolic adaptation to the chicken cecum. While there were no difference in the growth rate ofS . Kentucky andS . Typhimurium grown microaerophilically in cecal contents,S . Kentucky persisted longer when chickens were coinfected withS . Typhimurium. Thein vivo advantage thatS . Kentucky has overS . Typhimurium appears to be due to differential regulation of coreSalmonella genes via the stationary-phase sigma factorrpoS . Microarray analysis ofSalmonella grown in cecal contentsin vitro identified several metabolic genes and motility and adherence genes that are differentially activated inS . Kentucky. The contributions of four of these operons (mgl ,prp ,nar , andcsg ) toSalmonella colonization in chickens were assessed. Deletion ofmgl andcsg reducedS . Kentucky persistence in competition studies in chickens infected with wild-type or mutant strains. Subtle mutations affecting differential regulation of coreSalmonella genes appear to be important inSalmonella 's adaptation to its animal host and especially forS . Kentucky's emergence as the dominant serovar in poultry.