Abstract
BACKGROUND: Multiple incompatibility (Inc) groups of plasmids have been identified in Enterobacteriaceae species, but there are still quite a few sequenced plasmids that could not be assigned to any known Inc groups. METHODS: One IncFII(pKF727591)β plasmid p205880-qnrS and two Inc(pKPHS1) plasmids p11219-CTXM and p205880-NR1 were fully sequenced in this work. Detailed genomic comparison was applied to all available sequenced plasmids of IncFII(pKF727591) or Inc(pKPHS1) group. RESULTS: p205880-qnrS carried a novel transposon Tn6396, which was an ISKpn19-compsite transposon and represented a prototype transposable element carrying a minimum core qnrS1 module. p11219-CTXM harbored a novel transposon Tn6559, which was generated from integration of a truncated IS903D-bla (CTX-M-14) -ISEcp1 unit into the Tn3-family cryptic unit transposon Tn1722. Two Inc groups, IncFII(pKF727591) and Inc(pKPHS1), of plasmids from Enterobacteriaceae species were proposed, and IncFII(pKF727591) was further grouped into two subgroups IncFII(pKF727591)α and IncFII(pKF727591)β. Each of the 11 IncFII(pKF727591) plasmids carried multiple accessory modules including at least one resistance module, and the relatively small IncFII(pKF727591) backbones could acquire a wealth of foreign genetic contents. The modular structures of plasmid backbones were conserved within each of IncFII(pKF727591)α and IncFII(pKF727591)β subgroups but dramatically different, although with similar gene organizations, between these two subgroups. The Inc(pKPHS1) backbones were conserved with respect to modular structures, and only four of the 14 Inc(pKPHS1) plasmids carried accessory modules, two of which contained resistance genes. CONCLUSION: A genomic comparison of sequenced Inc(pKPHS1) or IncFII(pKF727591) plasmids provides insights into modular differences and genetic diversification of these plasmids, some of which carries antimicrobial resistance genes.