Phenotypic and genomic characteristics of clinical IMP-producing Klebsiella spp. Isolates in China

IMP-producing Klebsiella spp. (IMPKsp) strains have spread globally, including in China. Currently, the prevalence and genomic characterization of IMPKsp is largely unknown nationwide. Here we aimed to provide a general overview of the phenotypic and genomic characteristics of IMPKsp strains.

61 IMPKsp strains were obtained from 13 provinces in China during 2016-2021. All strains were tested for their susceptibility to antimicrobial agents by the microdilution broth method and sequenced with Illumina next-generation sequencing. We performed conjugation experiments on thirteen representative strains which were also sequenced by Oxford nanopore sequencing technology to characterize bla_IMP-encoding plasmids.

We find that all IMPKsp strains display multidrug-resistant (MDR) phenotypes. All strains belong to 27 different STs. ST307 emerges as a principal IMP-producing sublineage. bla_IMP-4 is found to be the major isoform, followed by bla_IMP-38. Seven incompatibility types of bla_IMP-encoding plasmids are identified, including IncHI5 (32/61, 52.5%), IncN-IncR (10/61, 16.4%), IncFIB(K)-HI1B (7/61, 11.5%), IncN (5/61, 8.2%), IncN-IncFII (2/61, 3.3%), IncFII (1/61, 1.6%) and IncP (1/61, 1.6%). The strains carrying IncHI5 and IncN plasmids belong to diverse ST types, indicating that these two plasmids may play an important role in the transmission of bla_IMP genes among Klebsiella spp. strains.

Our results highlight that multi-clonal transmission, multiple genetic environments and plasmid types play a major role in the dissemination process of bla_IMP genes among Klebsiella spp. IncHI5 type plasmids have the potential to be the main vectors mediating the spread of the bla_IMP genes in Klebsiella spp.