Carbapenem-resistant Klebsiella pneumoniae (CRKP) transfers conjugative plasmids containing blaNDM-5 and mcr-1 genes via outer membrane vesicles (OMVs)

Abstract A carbapenem-resistant Klebsiella pneumoniae (CRKP) strain, NFYY0065, was isolated from a fecal sample obtained from hospitalized patients in Nanfang hospital. By performing whole genome sequencing (WGS), we revealed that NFYY0065 harbored blaNDM-5 and mcr-1 genes, which were located on the IncX3 plasmid (pAN65-3) and IncHI2 plasmid (pAN65-1), respectively. Transfer of the blaNDM-5-bearing plasmid and mcr-1-bearing plasmid from NFYY0065 to Escherichia coli J53 conferred resistance to common beta-lactams and colistin on the transconjugants, respectively. Outer membrane vesicles (OMVs) obtained from the NFYY0065 strain were confirmed by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Purified vesicles harboring the blaNDM-5 and mcr-1 genes were confirmed by PCR/sequencing, and these OMVs derived from the NFYY0065 strain were transformed into ATCC700603 strains. The transformants were grown on co-antimicrobial plates (4 µg/ml meropenem and 4 µg/ml colistin), and further PCR/sequencing demonstrated that transformants carried the IncX3 plasmid and IncHI2 plasmid consistent with the plasmids of the original strain. This study highlights two points. It is the first report of co-expression of the blaNDM-5-IncX3 plasmid and mcr-1-IncHI2 plasmid in CRKP, and of the transfer of plasmids containing blaNDM-5 and mcr-1 genes via OMVs.