SUMMARY: The virulence region of the 50 MDa plasmid shared homology with 678 of 1021 salmonellae tested in colony hybridization experiments. The majority of and isolates tested hybridized with the region whereas, with the exception of and , other serotypes did not. Homologous virulence regions were plasmid encoded. In a common 60 MDa plasmid was present in all phage types tested but not in DT4, DT37 and DT170. Smaller plasmids showing partial homology were found in DT12, DT18, DT193 and DT204C. In a distinct plasmid profile for each of eight phage types was observed. Hybridizing plasmids were found in DT3, DT4, DT8, DT9 and DT11 whereas DT7, which was plasmid free, and DT10 and DT14, which harboured plasmids, did not hybridize. The extent of homology shared between and virulence plasmids was about 10 MDa and appeared conserved. Virulence plasmids from and did not show homology with a region of the 50 MDa plasmid which was not associated with virulence functions whereas plasmids of about 24 MDa and 38 MDa in some phage types did. The association of conserved virulence regions upon differing plasmids within salmonellae is discussed with reference to possible mechanisms of distribution and evolution of virulence genes.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error