STUDIES OF INHIBITION BETWEEN SALMONELLA STRAINS INFLUENCED BY A MUTATION IN THE CYDA GENE OF SALMONELLA-TYPHIMURIUM F98PHON

Previous investigations have demonstrated inhibition between salmonell a strains in broth cultures and in colonised caeca of young chickens. Stationary phase salmonella broth cultures and salmonella present in c aeca at high counts inhibit growth and colonisation, respectively, of secondary inoculated isogenic salmonella. This inhibition phenomenon c ould have considerable practical implications for the prevention of sa lmonella infection in poultry using live-attenuated salmonella vaccine s for day old chicks that are effective by an exclusion effect in the first days of life and then establish a long lasting immunity. Studies of the genetic basis of this inhibition problem are necessary in orde r to understand in greater detail its full practical protential. Tnpho A-mutants were created to knock out inhibition between isogenic field strains and to determine the influence of genes by identifying the ins ertion locus of the transposon. S. typhimurium F98 phoN Nal' cyd::Tnph oA (STM F98 GM129) is a strain with an insertion of TnphoA in the cydA gene which showed reduced inhibition in vitro. In vivo inhibition rem ained almost unaltered. The cyd operon encodes cytochrome-bd-ubiquinol oxidase, a membrane protein involved in energy provision under microa erophilic conditions.