Structural genomics of pNDM-BTR harboring In191 and Tn6360, and other bla _NDM-carrying IncN1 plasmids

Aim: To characterize a conjugative bla NDM-1-carrying plasmid pNDM-BTR from a clinical Escherichia coli isolate. Materials & methods: The complete nucleotide sequence of pNDM-BTR was determined using next-generation sequencing technology. Comparative genomic analysis of bla NDM-carrying IncN1 plasmids, including pNDM-BTR, was performed, and the antimicrobial resistance phenotypes were determined. Results: pNDM-BTR contained three accessory modules, namely IS26, a novel Tn3-family transposon Tn6360 and the dfrA14 region composed of In191, ecoRII–ecoRIImet and ΔIS1X2. The relatively small IncN1 backbones could integrate massive accessory modules, most of which were integrated at two ‘hotspots’. These IncN1 plasmids contained distinct profiles of accessory modules, which included those carrying various resistance genes. Conclusion: This study provides a deeper insight into horizontal transfer of resistance genes among IncN1 plasmids.