Emergence and genomic characterization of hypervirulent ST23/K1 <i>Klebsiella pneumoniae</i>: local epidemiology and global context

<h4>Introduction</h4>Hypervirulent <i>Klebsiella pneumoniae</i> (hvKp) of the K1/ST23 lineage is an emerging global threat associated with invasive community-acquired infections. Increasing reports of virulence-resistance convergence highlight the need for genomic surveillance, particularly within Europe where data remain limited. This study characterizes clinical K1/ST23 KP isolates circulating in the Czech Republic and compares them to a global genomic background to evaluate virulence architecture, resistance acquisition and plasmid evolution.<h4>Methods</h4>From 2017 to 2025, 570 <i>K. pneumoniae</i> isolates from a tertiary-care hospital were screened for hvKp markers. Ninety-six K1/ST23 isolates were subjected to long-read whole-genome sequencing and plasmid reconstruction. Genomes were analyzed alongside 2,463 international ST23 datasets using core-SNV phylogenomics, virulence/resistance profiling, and structural plasmid mapping. Chromosomal integrations were examined through analysis of flanking insertion-sequence contexts.<h4>Results</h4>The Czech K1/ST23 KP population exhibited high virulence uniformity (95/96 isolates scoring 9/9) without evidence of a single-clone outbreak, instead forming multiple phylogenetic lineages consistent with recurrent introductions. Eighty-three isolates carried pLVPK-like virulence plasmids; however, structural plasticity was prominent. The <i>iro</i> cluster was relocated to conjugative IncFII/rep_cluster_1418 plasmids in two isolates-one carrying additional AMR genes-and was chromosomally integrated via IS1-mediated recombination in three others. Iut was chromosomally integrated via IS903 (IS5 family) with either classical target-site duplication or recombination-associated insertion. Nine virulence-resistance fusion plasmids (IncFIB-IncFII-IncHI1B or IncC-based) were identified, representing early convergence toward MDR-hvKp.<h4>Conclusion</h4>K1/ST23 KP circulating in the Czech Republic is highly virulent yet genomically diverse, driven by active plasmid exchange, insertion-sequence-mediated chromosomal integration, and emerging virulence-resistance fusion plasmids. Although carbapenemase genes were absent, ESBL determinants and transmissible virulence loci indicate strong evolutionary potential toward MDR-hvKp. Continuous genomic surveillance and early intervention strategies are essential to mitigate future clinical impact.