Genomic characterization of a multidrug-resistant Citrobacter portucalensis isolate co-harboring blaKPC–2 and blaNDM–1 on distinct plasmids

作者：Junwei Huang, Kai Shen, Keqiang Chen, Junliang Wu, Yijun Zhu, Jingchao Shi · 发表于：Frontiers in Microbiology · 年份：2025 · DOI：10.3389/fmicb.2025.1633493 · 被引用次数：2 · 研究领域：Antibiotic Resistance in Bacteria、Vibrio bacteria research studies、Enterobacteriaceae and Cronobacter Research

Background Citrobacter portucalensis is an emerging multidrug-resistant (MDR) pathogen within the Citrobacter genus. Although individual occurrences of bla KPC– 2 or bla NDM– 1 have been sporadically reported, the coexistence of both carbapenemase genes in a single strain remains extremely rare. Methods We performed whole-genome sequencing and conjugation assays on a bloodstream isolate of C. portucalensis (JH112) obtained from a critically ill patient. Plasmid structure, resistance determinants, and transferability were comprehensively analyzed using in vitro assays and bioinformatic pipelines. Results JH112 exhibited an extensively drug-resistant phenotype and carried two major carbapenemase genes, bla KPC– 2 and bla NDM– 1 , located on distinct plasmids. The bla KPC– 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 bla NDM– 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 bla CMY– 49 and qnrB1 , contributing to broad-spectrum resistance. Conclusion We report a rare clinical C. portucalensis isolate co-harboring two carbapenemase genes on genetically di...