A large-scale genomic analysis of 43,722 Klebsiella pneumoniae genomes collected from 112 countries between 2011 and 2022 identified a marked epidemiological shift favoring the ST11-KL64 subclone among carbapenem-resistant strains. The ST11-KL64 lineage expanded rapidly after 2016 and overtook the KL47 variant as the dominant carbapenem-resistant K. pneumoniae (CRKP) subtype in China (40.5% for KL64 vs. 28.9% for KL47). Regional hotspots included Zhejiang and Sichuan provinces, where KL64 accounted for 62.3% and 58.7% of isolates, respectively. The authors link this expansion to genetic features that confer a fitness advantage related to plasmid-mediated virulence.
The investigation combined established genomic tools and hybrid assemblies to characterize strain and plasmid features. Analyses used Kleborate for lineage and virulence profiling, RAST for genome annotation, and PlasmidFinder for plasmid identification. Hybrid assembly approaches were applied to resolve plasmid-chromosome interactions and to determine whether virulence plasmids remained extrachromosomal or had undergone structural changes such as fusion or chromosomal integration.
The study focused on differences between capsular types KL64 and KL47 within ST11 carbapenem-resistant K. pneumoniae. Key virulence determinants evaluated included genes associated with hypervirulence such as aerobactin and the RmpADC regulatory locus. A notable finding was that 94.8% of KL64 isolates retained intact pLVPK-like virulence plasmids, and KL64 displayed higher aerobactin carriage (60.5%). In contrast, KL47 isolates had substantially lower aerobactin positivity (27.3%), consistent with altered plasmid status in that group.
Temporal analysis revealed KL64’s competitive replacement of KL47 after 2016, with geographic clustering in several Chinese provinces. The data show KL64’s rapid epidemiological ascent nationally and in regional pockets, supporting the interpretation that genetic differences affecting plasmid maintenance contributed to this spread. The global dataset across 112 countries provided the context for observing ST11-KL64’s international emergence during the 2011–2022 window.
Genomic characterization indicated that KL47 isolates more frequently experienced structural alterations to their virulence plasmids. Two dominant patterns in KL47 were documented: plasmid fusion events, notably with IncFIB[pNDM-Mar] elements (58.8% of KL47 cases showed such fusion), and chromosomal integration of plasmid sequences (41.4%). These events were associated with reduced apparent virulence potential compared with strains retaining intact extrachromosomal pLVPK-like plasmids.
Quantitative measures of plasmid-associated gene retention demonstrated a clear difference between the two capsular subtypes. KL64 strains exhibited superior plasmid stability, retaining 71.2% of plasmid-borne genes, whereas KL47 retained 43.6%. The high stability of pLVPK-like plasmids in KL64 correlated with sustained carriage of virulence determinants, enabling coexistence of hypervirulence factors and carbapenem resistance within the same genetic background.
The study reports a clinical correlation between the KL64 subclone and more severe patient outcomes. Specifically, KL64 infection was associated with increased odds of severe outcomes (odds ratio 2.34, 95% confidence interval 1.67–3.28). This association aligns with the higher frequency of intact virulence plasmids and aerobactin carriage in KL64, suggesting that plasmid-mediated virulence contributes to clinical severity among CRKP infections.
The authors conclude that the epidemiological success of ST11-KL64 stems from stable maintenance of pLVPK-like virulence plasmids, which permits simultaneous carriage of carbapenem resistance and hypervirulence genes. This combined phenotype presents a heightened public health threat, particularly in settings where vulnerable patients concentrate, such as critical care units. The findings underscore the need for genomic surveillance strategies that specifically track plasmid-mediated virulence in CRKP outbreaks. The study highlights plasmid stability and plasmid-chromosome dynamics as important surveillance targets because horizontal gene transfer and structural plasmid changes may accelerate evolution of high-risk clones.
Details beyond the genomic and epidemiological observations reported in the abstract—such as patient-level clinical management, mechanistic experimental validation, or prospective intervention outcomes—were not provided in the source summary. The primary message is that sustained extrachromosomal maintenance of pLVPK-like plasmids underpins ST11-KL64’s fitness advantage and global spread, calling for focused genomic monitoring of plasmid-mediated virulence alongside resistance surveillance in clinical and critical care settings.