Genomic characteristics and nosocomial transmission patterns of different capsular serotypes of Klebsiella pneumoniae sequence type 11 in a Chinese hospital

ABSTRACT Carbapenem-resistant Klebsiella pneumoniae , particularly sequence type 11 (ST11), has become the dominant epidemic clone in Asia. In this study, we collected 113 clinical ST11 isolates from a tertiary hospital in Beijing, China. Whole genome sequencing was performed, followed by capsular serotyping, resistome, and virulome analysis, and core-genome single nucleotide polymorphism-based phylogenetic and nosocomial transmission analysis. The aim was to elucidate the distribution of antimicrobial resistance genes, hypervirulence-associated genes, plasmid replicons, and phylogenetic relationships across different capsular serotypes within ST11 K. pneumoniae . Associations between the carriages of resistance and virulence genes and plasmid types were also investigated. The dominant capsular serotypes were KL64 (43, 38.1%), KL47 (37, 33.6%), and KL25 (29, 25.7%). The carbapenem resistance gene bla KPC-2 was nearly ubiquitous (93.8%) across all serotypes, while extended-spectrum β-lactamase genes showed serotype-specific patterns. The carriage of virulence genes differed markedly among serotypes and was linked to distinct plasmid profiles: KL64 isolates frequently harbored iucA (83.7%) and peg-344 (67.4%), whereas KL47 showed a higher prevalence of rmpA and rmpA2 , and KL25 rarely carried virulence genes. These virulence gene profiles were strongly associated with specific plasmid replicons, particularly IncFIB, IncHI1B, and IncR. Phylogenetic analysis revealed clear clustering by serotype, with varying intra-serotype diversity. We identified 20 potential nosocomial transmission events; KL25 was responsible for the majority of within-ward transmissions, while the Respiratory Medicine ward served as a central hub for both intra- and inter-ward spread across serotypes. Our findings reveal substantial genomic and epidemiological heterogeneity among ST11 capsular serotypes. IMPORTANCE Capsular polysaccharide (K antigen) serotypes are critical virulence determinants that influence clonal evolution and the emergence of carbapenem-resistant hypervirulent Klebsiella pneumoniae . The convergence of resistance and virulence determinants on mobile genetic elements represents a major evolutionary advantage for sequence type 11 (ST11) strains. In this study, our analyses of the distribution of antimicrobial resistance genes, hypervirulence-associated genes, plasmid replicons, and their associations across different capsular serotypes further highlighted the genomic diversity and potential molecular mechanisms associated with the different patterns of resistance and virulence genes across these serotypes. Our findings provide further evidence and suggest that different capsular serotypes may represent distinct evolutionary trajectories within the ST11 lineage. These serotypes also exhibited different patterns during transmission. The acquisition of diverse plasmids might drive the convergence of resistance and virulence and shape serotype-specific transmission dynamics. These results underscore the necessity of integrated genomic surveillance to monitor high-risk clones in healthcare settings.