Genome-wide insight into the evolution and global transmission of tigecycline resistant tet(X4)-carrying Klebsiella species across reservoirs.

OBJECTIVES

The emergence of plasmid mediated tet(X4) gene compromises the clinical utility of tigecycline and underscores growing concerns regarding its environmental reservoirs and potential for interspecies transmission, particularly within Klebsiella species. The aim of this study is to elucidate the dissemination patterns and evolutionary relationships of tet(X4)-harbouring plasmids across clinical and environmental Klebsiella isolates.

METHODS

We conducted a comprehensive phylogenetic analysis integrating both newly sequenced plasmids and publicly available datasets from the NCBI Plasmid database. Conjugation assays were performed to assess the horizontal transfer potential of tet(X4)-harbouring plasmids. Furthermore, globally sourced genomic data of tet(X4)-carrying Klebsiella strains were subjected to infer their spatiotemporal distribution, transmission dynamics, and the time to the most recent common ancestor (tMRCA) using BEAST.

RESULTS

The tet(X4) gene was located on conjugative plasmids ranging from 5.7 kb to 19.3 kb, predominantly embedded within a conserved abh-tet(X4)-ISCR2 structure flanked by mobile genetic elements such as IS26 and IS1, which likely facilitate horizontal gene transfer and plasmid integration. These plasmids commonly co-harboured multiple ARGs, including aadA1, floR, and tet(A). The tet(X4)-carrying Klebsiella isolates exhibited substantial genetic diversity, with ST534 and ST3393 identified as the most prevalent lineages. The tet(X4)-carrying K. pneumoniae strains exhibited clonal dissemination across clinical and environmental reservoirs, with the estimated tMRCA dating back to 1873. Moreover, the co-occurrence of tet(X4) with carbapenemase or colistin resistance genes highlights the significant public health threat posed by these high-risk strains.

CONCLUSIONS

These findings highlight the urgent need for coordinated genomic surveillance under a One-Health framework to monitor and mitigate the global spread of multidrug-resistant tet(X4)-carrying Klebsiella isolates.