Convergence of Plasmid-Mediated tmexCD-toprJ With Critical Resistance Genes Fuels Spread of Multidrug Resistant...

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.