Global epidemiological and genetic characteristics of carbapenem-resistant Escherichia coli carrying blaIMP.

Carbapenem-resistant Escherichia coli (CREC) is a serious global health threat. While blaNDM-positive and blaKPC-positive CRECs are well-characterized, the genomic and epidemiological features of blaIMP-positive CRECs remain poorly understood. This study provides a comprehensive analysis of blaIMP-positive CRECs by integrating local and global surveillance data. We characterized nine blaIMP-4-positive CRECs from 94 CRECs collected from four tertiary hospitals in Zhejiang, China (2017-2024), using whole-genome sequencing and assays for antimicrobial susceptibility, plasmid transfer, stability, and fitness. The nine isolates were multidrug-resistant but susceptible to colistin, tigecycline, and amikacin. Seven diverse sequence types (STs) were identified, with high-risk ST1193 clones being first detected. The isolates had similar blaIMP-carrying IncN plasmids with high conjugation frequencies (5.3 × 10-2 to 8.7 × 10-1), 100% stability after 100 generations, and minimal fitness cost, facilitating regional dissemination. In addition to plasmids, other mobile genetic elements, like class 1 integrons, transposons, and insertion sequences, can also facilitate the horizontal transfer of blaIMP genes. Global analysis of 340 blaIMP-positive CRECs revealed high genetic diversity (82 STs), with ST131 predominant (36.18%). Clonal spread was observed for ST131 and ST216. Significant positive correlation existed between antibiotic resistance genes and plasmid replicons (r = 0.5205, P < 0.001), highlighting plasmids' role in resistance transmission. China, Japan, and Australia were the top 3 contributing countries, which also showed relatively diverse resistance genes but similar virulence factors. These findings emphasize the evolving risk of blaIMP-positive CRECs and underscore the need for sustained genomic surveillance. IMPORTANCE: Compared with blaNDM-positive and blaKPC-positive carbapenem-resistant Escherichia coli (CREC), blaIMP-positive CRECs are often overlooked. This study emphasized IncN plasmids, which, with their strong transferability, stability, and low fitness cost, can serve as vectors for the widespread dissemination of blaIMP genes. Additionally, the study elucidated the global epidemiological status, transmission features, and potential threats of blaIMP-positive CRECs through a large-scale analysis of publicly available genomic data. These findings not only facilitate a better understanding of the genetic dynamics and transmission pathways of blaIMP but also help develop effective regulatory measures and antibiotic stewardship programs to alleviate the increasingly severe burden of antimicrobial resistance.