ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Infectious Agents and Disease
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1633493
Genomic Characterization of a Multidrug-Resistant Citrobacter portucalensis Isolate Co-harboring bla KPC-2 and bla NDM-1 on Distinct Plasmids
Provisionally accepted
- Jinhua Central Hospital, Jinhua, China
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Citrobacter portucalensis is an emerging multidrug-resistant (MDR) pathogen within the Citrobacter genus. Although individual occurrences of blaKPC-2 or blaNDM-1 have been sporadically reported, the coexistence of both carbapenemase genes in a single strain remains extremely rare.We performed whole-genome sequencing and conjugation assays on a bloodstream isolate of C. portucalensis (JH-112) obtained from a critically ill patient. Plasmid structure, resistance determinants, and transferability were comprehensively analyzed using in vitro assays and bioinformatic pipelines.JH-112 exhibited an extensively drug-resistant phenotype and carried two major carbapenemase genes, blaKPC-2 and blaNDM-1, located on distinct plasmids. The blaKPC-2 gene resided on an IncFII(Yp)-type plasmid (~110 kb) with a complete conjugation module and was successfully transferred to a recipient strain. This plasmid also harbored an O-antigen biosynthesis gene cluster, potentially enhancing host adaptation. In contrast, the blaNDM-1 gene was located on a 340 kb IncHI2/HI2A-type megaplasmid with incomplete conjugation machinery and failed to transfer under standard conditions. Both plasmids showed unique structural arrangements compared to known references. The chromosome also carried blaCMY-49 and qnrB1, contributing to broadspectrum resistance.We report a rare clinical C. portucalensis isolate co-harboring two carbapenemase genes on genetically distinct plasmids with divergent mobility. This highlights the species' potential role as a resistance gene reservoir and the need for enhanced molecular surveillance in both clinical and environmental settings.
Keywords: Citrobacter portucalensis, blaKPC-2, BlaNDM-1, Plasmid-mediated resistance, antimicrobial resistance, conjugation
Received: 22 May 2025; Accepted: 01 Jul 2025.
Copyright: © 2025 Huang, Shen, Chen, Wu, Zhu and Shi. 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:
Yijun Zhu, Jinhua Central Hospital, Jinhua, China
Jingchao Shi, Jinhua Central Hospital, Jinhua, China
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