Preliminary Characterization of TnphoA Mutants of Salmonella Enteritidis with Reduced Invasiveness in vivo
Several groups have studied the genetic basis of epithelial cell entry by Salmonella species using an in vitro system of cultured monolayers.1,2,3 The aim of this study was to examine the molecular basis of in vivo invasivness as opposed to in vitro invasiveness of a phage type 4 strain of S.enteritidis. Using the day old chicken model the genetic basis for in vivo invasiveness was studied by identifying mutations which affect this phenotype. In vivo invasiveness was defined as the ability of organisms to penetrate the intestinal epithelial cells following oral inoculation and localise in the spleen within 24h. Approximately 500 TnphoA insertion mutants of S.enteritidis S13 were examined. Seven TnphoA mutants were identified as being less invasive by a low rate of isolation of the organisms from the spleen 24h after oral inoculation (13% -47% of chicks inoculated) compared to the parent strain and an invasive TnphoA mutant (76%-87% respectively).