Whole-genome sequence analysis of a clinical hypervirulent Klebsiella variicola strain recovered from a hospital in Ningxia, China.

Klebsiella variicola (KV) infections are being increasingly reported across diverse geographic regions and linked to high mortality. KV displays substantial geographical heterogeneity in antimicrobial resistance profiles, virulence phenotypes, and genetic backgrounds; genetic variants further promote its adaptability to varied environments. In this study, we isolated a strain designated KV7 from the sputum sample of an ICU patient at a tertiary hospital in Ningxia, China, with species confirmation achieved via whole-genome sequencing. Antimicrobial susceptibility testing was performed using the VITEK 2 Compact automated microbial system. String test, immune cell phagocytosis assay, serum resistance assay, and mouse infection model were applied to evaluate virulence phenotypes. Genomic characterization revealed that KV7 belongs to ST8223 with an unassigned KL type and exhibits hypervirulence while remaining susceptible to tested antibiotics. Its hypervirulence is associated with the virulence plasmid pKV7-vir, which carries numerous virulence factor genes. Multiple mobile genetic elements were also detected on pKV7-vir. Moreover, comparative genomic analysis of KV isolates from China and other countries was performed, laying a theoretical foundation for regional surveillance of this pathogen.