Genetic Characterization of an ST5571 Hypervirulent Klebsiella pneumoniae Strain Co-Producing N DM-1, MCR-1, and OXA-10 Causing Bacteremia

Purpose: To investigate the phenotypic and genomic characteristics of the multi-drug resistant and hypervirulent Klebsiella pneumoniae strain recovered from bacteremia. Methods: Antimicrobial susceptibility testing (AST) was performed by the microdilution method. Antimicrobial resistance genes, virulence-associated genes, multilocus sequence typing (MLST), and plasmid replicon were characterized by next-generation sequencing (NGS) and nanopore sequencing. S1 nuclease-pulsed field gel electrophoresis (S1-PFGE) and Southern blotting were performed to characterize the plasmid profile. Results: The hypervirulent colistin- and carbapenem-resistant K. pneumoniae strain DY2009 was identified as ST5571, co-carrying mcr-1, bla(NDM-1), and bla(OXA-10). In silico analysis found that it was K2 serotype. AST results revealed that DY2009 was resistant to carbapenems, cephalosporins, ciprofloxacin, chloramphenicol, and colistin but remained susceptible to aztreonam, gentamicin, amikacin, and tigecycline. Through the whole-genome analysis, a variety of virulence determinants were identified, including rmpA. Plasmid analysis confirmed that the mcr-1 and bla(NDM-1) gene harbored a similar to 33 kb IncX4 plasmid and a similar to 44 kb IncX3 plasmid. In contrast, bla(OXA-10) was encoded by chromosome. Conclusion: To the best of our knowledge, we first report the clinical hypervirulent K. pneumoniae isolate co-producing MCR-1, NDM-1, and OXA-10 causing bacteremia. We found that mcr-1 and bla(NDM-1) genes were located on two self-conjugative epidemic plasmids, contributing to the widespread MCR-1 and NDM-1 in China. The results of this work improve our understanding of the genetic background of colistin- and carbapenem-resistant K. pneumoniae isolate from bacteremia and the resistance mechanisms. Our findings highlight the urgent need for infection control of such strain to prevent it from becoming an extensive-drug resistant clone.