The role of plasmid genes in the pathogenicity of Salmonella dublin

The virulence (expressed as LD50 values) for mice of two mutant strains of Salmonella dublin, both containing TnA insertions in the resident plasmid, was reduced by 10(4)-10(5) when infection was by the oral or intravenous or intraperitoneal route. When the plasmid was lost from one of the mutants no further decrease in virulence was observed. Results also suggested that plasmid genes are not involved in the ability of S. dublin to cross the gut wall.