Characterization of an NDM-5-producing hypervirulent Klebsiella pneumoniae sequence type 65 clone from a lung transplant recipient.

The emergence of New Delhi Metallo-β-lactamase (NDM)-producing Klebsiella pneumoniae has aroused critical concern worldwide. Herein, we reported the first emergence of NDM-5-producing K. pneumoniae isolates in a 68-year-old lung transplant recipient, who died of septic shock 13 days after surgery. The K. pneumoniae strain KP22937 isolated from the bloodstream of the patient was analyzed for phenotypes and genotypes. KP22937 belonged to sequence type (ST) 65 and capsule serotype K2, contained iucABCDiutA and iroBCDN virulence clusters, showed high virulence to mice, and was therefore considered a hypervirulent K. pneumoniae. The blaNDM-5 gene was located on a genomic island region of the IncX3-type plasmid pNDM22937, which was successfully transferred to Escherichia coli EC600 with insignificant fitness costs. The transconjugant demonstrated similar antimicrobial susceptibility and growth kinetics to the recipient E. coli EC600. The plasmid pNDM22937 was almost identical to the blaNDM-5-carrying IncX3 plasmids previously reported in K. pneumoniae strains with different ST types and in other species. Our findings raise concerns about the horizontal spread of blaNDM-5 gene mediated by IncX3 plasmid, where hypervirulent K. pneumoniae strains are also involved. Stricter control measures are needed to prevent the dissemination of the novel clone in hospital settings.