Clonal transmission of blaIMP-4-carrying ST196 Klebsiella pneumoniae isolates mediated by the IncN plasmid in China

Objectives

To investigate the clinical and molecular epidemiological characteristics of bla_IMP-4-carrying Klebsiella pneumoniae in a tertiary hospital in China.

Methods

Ten carbapenem-resistant K. pneumoniae (CRKP) isolates carrying the bla_IMP-4 gene were collected. Molecular characteristics were analysed using whole-genome sequencing. Plasmid conjugation experiments were used to analyse conjugation of the plasmids. We compared and analysed K. pneumoniae-carrying bla_IMP-4 genomic datasets obtained from the National Center for Biotechnology Information (NCBI) with the strains in this study.

Results

All 10 CRKP isolates carrying bla_IMP-4 were collected from 10 adult patients in the respiratory intensive care unit. These strains were only sensitive to polymyxins and tigecycline due to them simultaneously carrying multiple resistance genes, namely bla_OKP-A-5, fosA, oqxA, and oqxB. Notably, R29 harboured two carbapenemase genes (bla_NDM-1 and bla_IMP-4). These strains had similar drug-resistant phenotypes and genes, all belonging to sequence type (ST)196. Additionally, the patients had experienced spatiotemporal intersection during hospitalization, suggesting that these strains underwent clonal transmission, but they belonged to different clonal clusters from the bla_IMP-4-positive K. pneumoniae currently published in the NCBI. Among the 10 strains, bla_IMP-4 was located on the IncN plasmid, and six strains had successfully transferred the plasmid to the recipient strain EC600 through plasmid conjugation.

Conclusions

The bla_IMP-4-positive ST196 CRKP isolate showed clonal distribution in the respiratory intensive care unit, which was mediated by the IncN plasmid. Consequently, there should be increased monitoring of carbapenem-resistant strains in clinical settings to prevent and control its transmission.