Presence of F-like OriT base-pair sequence on the virulence plasmids of Salmonella serovars Gallinarum, Enteritidis, and Typhimurium, but absent in those of Choleraesuis and Dublin.

The 90 kb virulence plasmids of Salmonella biosers Gallinarum and Pullorum (expressed as serovar Gallinarum) are non-conjugative. They were, however, found to be readily mobilized by IncFI and IncFIV plasmids, but not by conjugative IncA, IncB = C, IncH, IncL and IncM R plasmids. No virulence plasmids of serovars Choleraesuis, Dublin, Enteritidis, and Typhimurium were mobilized by any of these conjugative plasmids. The 90 kb virulence plasmid of Gallinarum was shown to hybridize to the Tra genes region of IncFI and IncFIV plasmids, suggesting it contains some F Tra genes region. It also hybridized with 75% homology to the virulence plasmid of Typhimurium, and, in decreasing order, to those of Dublin, Enteritidis, and Choleraesuis. A probe made of 319 basepairs of the F OriT region hybridized with approximately 45% homology to the virulence plasmid of Gallinarum, 63% to that of Typhimurium and 50% to that of Enteritidis. The probe, however, failed to hybridize to the plasmid DNAs of IncA, IncB = C, IncH, IncL and IncM, and to the virulence plasmids of Choleraesuis and Dublin.