Localization by insertion mutagenesis of a virulence-associated region on the Salmonella typhimurium 96 kilobase pair plasmid.

The virulence-associated plasmid pEX102 of Salmonella typhimurium line TML R66 was tagged with the transposon Tn5 and the virulence of the mutants obtained was assayed in the mouse salmonellosis model. Out of 36 independent insertion mutants tested two isolates had clearly reduced virulence in (CBA x C57B1/6)F1 mice. The corresponding Tn5 elements were positioned on the restriction endonuclease map of pEX102 and found to be some 4 kilobases apart (kb) on the 96 kb virulence plasmid.