ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Antimicrobials, Resistance and Chemotherapy
This article is part of the Research TopicDefending the Last Line: Combatting Carbapenem-Resistant PathogensView all 17 articles
Coexistence of blaNDM-1 and blaIMP-4 in an IncHI5 Plasmid Harboured by Carbapenem-resistant Raoultella ornithinolytica
Provisionally accepted
- Henan Provincial Cancer Hospital, Zhengzhou, China
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Background Raoultella ornithinolytica is an emerging pathogen. This study aimed to characterise the genomic and molecular features of a carbapenem-resistant R.ornithinolytica strain co-harbouring blaNDM-1 and blaIMP-4. Methods Strain he2023 was identified and subjected to antimicrobial susceptibility testing using the BD Phoenix-M50 fully automated system. The strain was verified using MALDI-TOF. Carbapenemase genes were confirmed by PCR. Whole-genome sequencing (WGS) was performed to identify resistance genes and plasmid types. Conjugation experiments were conducted to assess transferability, and plasmid stability was evaluated through serial subculturing. 2 Results The BD Phoenix-M50 system misidentified strain he2023 as Klebsiella pneumoniae, whereas MALDI-TOF and WGS correctly identified it as R.ornithinolytica. The strain was resistant to most antimicrobial agents, remaining susceptible only to amikacin ,Tigecycline and polymyxin B. The blaNDM-1 and blaIMP-4 genes were both located on the plasmid pNDM-IMP, which belongs to the replicon type IncHI5. The blaNDM-1 was embedded within the transposon TnAS3, with the genetic context ISCR1-sul1-aph(3')-VI-ISAba125-blaNDM-1-bleMBL-trpF-dsbC-ISCR1. The blaIMP-4 was located downstream of blaNDM-1 within a novel class 1 integron (In1965) carrying the structure sul1-qacE-arr-3-ltrA-blaIMP-4-IntI1. Conjugation and transformation assays showed that the plasmid pNDM-IMP was non-transferable but exhibited high structural stability. Conclusion This study is the first to report an IncHI5 plasmid co-harbouring blaNDM-1 and blaIMP-4 in R.ornithinolytica. Non-transferable plasmids may serve as reservoirs or initial carriers for antibiotic resistance genes.Our findings highlights the importance of mobile genetic elements in the formation of multidrug resistance.
Keywords: blaIMP-4, BlaNDM-1, carbapenemase, IncHI5 plasmid, Raoultella ornithinolytica
Received: 11 Nov 2025; Accepted: 20 Jan 2026.
Copyright: © 2026 Qu, Xiao, Chang, Sun, Li and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Qingxia Xu
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