[Pangenome analysis on plasmids carried by hypervirulent Klebsiella pneumoniae]

Objective: To analyze the pangenome, pan drug resistance genes, pan virulence genes, pan replicons, and others of the plasmids carried by hypervirulent Klebsiella pneumoniae (hvKP) in the world and their evolutionary trends over time, and provide evidence for more comprehensive understanding of the evolution of genetic diversity, drug resistance genes, and virulence genes of the plasmids. Methods: From the National Center for Biotechnology Information database, a total 1 738 plasmids were screened from 524 strains with completed genome sequences in 2 136 strains of hvKP carrying plasmids. Through pangenome, pan drug resistance gene, and pan-virulence gene composition and functional analyses, the curves of pangenome size and new gene size against plasmid isolation time were established, revealing the diversity of the plasmid pangenome and its evolutionary patterns. Results: The homologous genes, homologous drug resistance genes, homologous virulence genes, and replicons of the plasmids carried by hvKP comprised of 12 906, 149, 107 and 89 types, respectively. The fitting curves for the number of new genes, new drug resistance genes and new replicons increased with the increase of plasmids in an open state, while the curve for novel virulence genes was in a closed state. A obvious increase in new drug resistance genes was observed during 2018-2019. Among the newly added drug resistance genes during 2021-2023, beside those conferring aminoglycoside resistance, they were mainly new subtypes conferring carbapenem resistance. Conclusions: The pangenome of plasmids carried by hvKP exhibited high diversity, with the plasmid pan genes, pan drug resistance genes, and pan replicon types gradually expanding, while the pan virulence genes remains stable. The increase in novel drug resistance genes in specific years and the emergence of new carbapenem-resistant gene subtypes during 2021-2023 suggested the need for strengthened drug resistance surveillance and prevention efforts, with particular attention to carbapenem resistance.