Fig. 1

Transfer of the mobilizable MDR plasmid pKPHS3 (p3) and the virulence plasmid pRJF293 (pV), both lacking relaxase genes, with the help of the conjugative CR plasmid pKPHS2 (p2). a Schematic diagram of the two rounds of conjugation assays. The green square denotes the tra gene cluster on pKPHS2. The green square with white slashes denotes the incomplete tra gene cluster on pKPHS3. The red line indicates the transconjugants generated from K. pneumoniae RJF293-p2 conjugated with K. variicola KvBSI002A. b The conjugation frequencies of pKPHS2, pKPHS3 and pRJF293. The donor strains were HS11286, RJF293-p2, and RJF293-p2-p3. The recipient strains were RJF293 and KvBSI002A. Detailed data are available in Additional file 6: Table S5. c XbaI PFGE and S1-PFGE of transconjugants and their parental strains. M represents the molecular weight marker Salmonella serotype Braenderup H9812. Strains with the same symbol on the PFGE image represent the progeny derived from the same parental strain. The red lines present the transconjugants generated from RJF293-p2 with KvBSI002A. The CR plasmid, MDR plasmid, and virulence plasmid on the S1-PFGE image are indicated by blue triangles, purple triangles, and red triangles, respectively. The plasmids and strains were further confirmed by PCR