Convergence of Plasmid‐Mediated tmexCD‐toprJ With Critical Resistance Genes Fuels Spread of Multidrug Resistant Bacteria

ABSTRACT

The plasmid‐mediated tigecycline resistance cluster tmexCD‐toprJ is an emerging clinical threat whose convergence with carbapenemase and colistin resistance determinants may compromise multiple last‐line therapies. We analyzed 1227 tmexCD‐toprJ ‐positive genomes from 42 countries and 16 genera, including 1189 public genomes and 38 newly sequenced clinical isolates. The increase was most pronounced in China, where tmexCD‐toprJ prevalence rose from 0.282% before 2011 to 1.504% after 2020, and approximately half of post‐2015 Chinese isolates were classified as dual‐positive, co‐harboring bla _NDM , bla _KPC , or mcr . tmexCD‐toprJ was mainly plasmid borne and distributed across diverse Klebsiella and Pseudomonas lineages and plasmid backbones. Dual‐positive plasmids showed distinct contexts: acquisition of tmexCD‐toprJ by pre‐existing bla _KPC ‐ or mcr ‐positive IncF backbones, and remodeling of multiple resistance regions in tmexCD‐toprJ ‐ bla _NDM IncU/IncHI1B plasmids. Ecological distributions also differed; bla _NDM combinations spanned human, animal, and environmental sources, whereas bla _KPC and mcr combinations were mainly human and animal associated, respectively. Clinical isolates experiment confirmed resistance to the corresponding antibiotic classes, stable maintenance of dual‐positive plasmids, and transferability of a subset of plasmids. Under antibiotic pressure, the tmexCD‐toprJ region was mobilized across plasmids into a bla _KPC plasmid. These findings reveal multiple evolutionary routes driving convergence of last‐line resistance determinants and highlight the need for integrated genomic and phenotypic surveillance.