Emergence of conjugative metallo-β-lactamase-encoding plasmids in the Klebsiella pneumoniae species complex: First identification of IMP-8-MCR-9.1 in K. quasipneumoniae and VIM-1 in K. variicola in Taiwan

Background: This study aims to investigate the prevalence of carbapenemase genes in the Klebsiella pneumoniae species complex (KpSC) in Taiwan. Methods: We analyzed 1226 carbapenem-resistant KpSC (CRKpSC) from three hospitals across Taiwan to assess carbapenemase gene prevalence and the distribution of carbapenem-resistant K. quasipneumoniae (CRKq) and carbapenem-resistant K. variicola (CRKv). Whole-genome sequencing, conjugation assays, and a larvae infection were used to characterize metallo-β-lactamase-carrying plasmids in CRKq and CRKv. Results: Among the CRKpSC isolates, 246 (20.1 %) carried bla_KPC, 42 (3.4 %) bla_OXA-48, and three carried both. Only 12 (1.0 %), 8 (0.7 %), and 6 (0.5 %) carried bla_IMP, bla_NDM, and bla_VIM, respectively. Of all CRKpSC isolates, six were Kq and one was Kv; only one Kq (NCKUH114) carried bla_IMP and one Kv (NTUH73) carried bla_VIM. pNCKUH114–1 (305,605 bp), an IncHI2/IncHI2A plasmid, encoded bla_IMP-8 and mcr-9.1, while pNTUH73–1 (284,771 bp), a repFIB/repHI5B plasmid, carried bla_VIM-1. The most similar plasmid in the NCBI database showed 94 % coverage for pNCKUH114–1 and less than 35 % for pNTUH73–1. Under our experimental conditions, both plasmids could be transferred only into E. coli EC359, but this did not enhance its virulence in larvae. Conclusions: We firstly report the presence of conjugative carbapenemase-carrying plasmids in Kq and Kv in Taiwan. The recombination and dissemination of these plasmids warrant close monitoring.