Genomic characterisation of ST11-KL19 carbapenem-resistant Klebsiella pneumoniae carrying dual carbapenemases and hypervirulence-associated markers.

OBJECTIVES: The global convergence of multidrug resistance and hypervirulence in Klebsiella pneumoniae poses a critical public health threat. While ST11-KL64 has historically dominated in China, the evolutionary dynamics driving the emergence of novel high-risk sublineages remain poorly understood.

METHODS: We analysed 304 non-duplicate carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates collected in Zhejiang Province, China, during 2024-2025 using antimicrobial susceptibility testing, whole-genome sequencing, plasmid analysis, and phylogenetic reconstruction. Publicly available genomes were incorporated for comparative genomic and phylogenetic analyses.

RESULTS: ST11 was the dominant sequence type, and KL19 showed a higher detection frequency in 2025 than in 2024 in this single-centre collection. A distinct ST11-KL19 clade predominated among dual-carbapenemase isolates, mainly co-harbouring blaKPC-2 and blaNDM-1, with a significant increase in blaNDM-1 carriage in 2025. Most dual-carbapenemase ST11-KL19 isolates also carried multiple hypervirulence-associated markers and exhibited very high resistance rates to polymyxin B and frequent resistance to tigecycline. In dual-carbapenemase-producing ST11-KL19 isolates, plasmid analysis suggested that virulence-associated genes were linked to IncHI1B-FIB(K)-like plasmids, whereas blaKPC-2 and blaNDM-1 were linked to IncFII(pHN7A8)-IncR-like and IncN-like plasmids, respectively. Correlation analyses demonstrated coordinated accumulation of resistance and virulence determinants specifically in rmpA-intact ST11-KL19 isolates. In the global ST11-KL19 phylogeny, the C2e subcluster showed a higher burden of antimicrobial resistance genes and hypervirulence-associated markers than other subclusters.

CONCLUSIONS: ST11-KL19 represents a CRKP background with increased local detection and frequent carriage of dual carbapenemases, hypervirulence-associated markers, and resistance to last-line agents. These findings support enhanced genomic surveillance of ST11-KL19, while multicentre longitudinal studies and functional assays are required to define its transmissibility, virulence phenotype, and evolutionary trajectory.