Huang, Ying-ChiYing-ChiHuangHuang, Tzu-WenTzu-WenHuangRahi, PraveenPraveenRahiKuo, Shu-ChenShu-ChenKuoChen, Yan-RuYan-RuChenCHI-TAI FANG2026-03-232026-03-232026-12https://scholars.lib.ntu.edu.tw/handle/123456789/736561Extensively drug-resistant gram-negative bacteria harbouring dual resistance to carbapenems and colistin represent a critical global health threat. A total of 929 population-representative isolates were systematically collected from 29 hospitals across four regions of Taiwan between 2010 and 2020. Forty-one isolates (4.4%) were nonsusceptible to carbapenems and underwent whole-genome sequencing, resistance gene profiling, plasmid analysis, and antimicrobial susceptibility testing (AST). Among them, 35 isolates (85.4%) exhibited dual resistance to carbapenems and colistin; however, only half (17/35) were detectable by standard phenotypic AST. Colistin resistance was primarily mediated by activation of the chromosomal operon, which was frequently inducible and often undetected by standard testing, rather than by or . A conserved IncHI2 plasmid carrying and persisted and circulated across species for over a decade. Species-specific resistance patterns were observed: typically exhibited colistin resistance despite lacking carbapenemases, whereas commonly carried and occasionally lacked the operon. Both species exhibited comparable imipenem nonsusceptibility, complicating therapeutic decision-making. The convergence of carbapenem and colistin resistance in a substantial proportion of isolates at the population level makes this genus an emerging priority for hospital infection control and antimicrobial resistance surveillance. These findings underscore the urgent need for improved diagnostics, strengthened antimicrobial resistance surveillance, and optimized treatment strategies.enEnterobacter sppIncHI2 plasmidarn operoncarbapenem resistancecolistin resistancemcr-10mcr-9journal article10.1080/22221751.2026.262369341665622