Background: Klebsiella pneumoniae resistant to both carbapenems and colistin imposes severe challenges for management. In this study, we report a cluster of 5 carbapenem-resistant K pneumoniae clinical strains belonging to ST1 and K57 types, 4 of which were also resistant to colistin, from 2 hospitals.
Methods: The 5 strains were subjected to whole-genome sequencing (WGS) using the short-read Illumina HiSeq platform, and 2 strains were also selected for long-read WGS using MinION. Clonal relatedness of the 5 strains was determined based on single-nucleotide polymorphisms (SNPs). Conjugation experiments were performed to obtain self-transmissible plasmids.
Results: All 5 strains carried the carbapenemase-encoding gene blaNDM-1, whereas the 4 colistin-resistant strains also harbored a new variant of the mcr-8 colistin resistance gene, namely, mcr-8.2. MCR-8.2 differs from MCR-8.1 by four amino acid substitutions (A51V, A232S, N365Y, and N480K). mcr-8.2 was located on a large, hybrid, nonself-transmissible plasmid containing IncQ, IncR, and IncFII replicons, whereas blaNDM-1 was carried by self-transmissible IncX3 plasmids. Phylogenetic analysis based on SNPs revealed that the 5 strains were likely to have a common origin.
Conclusions: Both the intra- and interhospital transfer of strains carrying mcr-8 and blaNDM-1 were identified, which represents an emerging threat for clinical management and infection control.
Keywords: Klebsiella pneumoniae; mcr; colistin resistance; plasmid.
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