Global epidemiological trend of Klebsiella pneumoniae ST23: Emergence of KL57 lineage carrying dual carbapenemases.

Klebsiella pneumoniae is an opportunistic pathogen responsible for both hospital and community-acquired infections. It is broadly classified into classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp), with the latter being linked to increased mortality owing to its capacity for invasive and metastatic infections. The recent global emergence of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKp) strains poses a serious and escalating public health threat worldwide. In this study, we conducted a comprehensive genomic analysis of all publicly available ST23 genomes (n = 1,622) from the NCBI database, collected between 1980 and 2024, to investigate the evolutionary dynamics and global dissemination of this emerging high-risk clone. We systematically analysed antimicrobial resistance profiles, virulence factors, plasmid content, and phylogenetic relationships, with particular emphasis on the emerging CR-hvKp ST23-KL57 lineage. ST23 strains were identified in 42 countries, including 263 CR-hvKp ST23 strains (16.2% of the total), which were detected in 22 countries. Although both ST23-KL1 (n = 1,577) and ST23-KL57 (n = 45) belong to the same sequence type, phylogenetic analysis revealed substantial single-nucleotide polymorphism (SNP) divergence, classifying them into two distinct sublineages (SLs): ST23-KL1 (SL23) and ST23-KL57 (SL218). The newly emerged ST23-KL57 strains exhibited higher levels of antimicrobial resistance, smaller genome sizes, lacked key chromosomal virulence loci (GIE492 and all_island), and were predominantly distributed in Europe. Notably, 77.8% of ST23-KL57 strains were identified as CR-hvKp, underscoring the alarming convergence of carbapenem resistance and hypervirulence. These findings reveal the emergence of a highly adaptive international clone and highlight the urgent need for enhanced global surveillance efforts and more granular sublineage-level genomic characterisation to inform public health responses and clinical management.