Abstract
PURPOSE: NDM-1-producing Citrobacter portucalensis and Citrobacter freundii simultaneously occurred in a hospital. This study aims to characterize the bla (NDM-1-)carrying plasmids in these Citrobacter strains. METHODS: Cf7303, Cf7308, and Cf7313 were recovered from three patients in a teaching hospital from September 24 to October 1, 2021. Bacteria were identified by MALDI-TOF mass spectrometry, and antibiotics susceptibility tests were determined by VITEK(®) 2 compact system. Whole-genome sequencing (WGS) was performed using the HiSeq Illumina and QNome platform to characterize the genomes. RESULTS: Cf7303 was identified as C. portucalensis Sequence Type 328 by WGS, and harbored two plasmids, namely pCf7303 and a novel IncFIB pNDM-Cf7303 on which antibiotic-resistant genes (bla (TEM-1), bla (CTX-M-14), bla (NDM-1), aac (3)-IId, aadA2, fosA3, sul1, sul2, catA2, tetD, dfrA12, qacEdelta1, mph(A), and ble (MBL)) are located. C. freundii strain Cf7308 and Cf7313 belonged to the same Sequence Type 98. Cf7308 contained two plasmids, pCf7308, and an IncN1 pNDM-Cf7308 with homology to pNDM-BTR in E. coli and pNDM-CWH001 in C. freundii. CONCLUSION: We characterized a putatively novel IncFIB plasmid carrying bla (NDM-1) in C. portucalensis. In addition, the closely related bla (NDM-1)-carrying IncN1 plasmids in E. coli and C. freundii suggest that interspecies or intraspecies horizontal transfer occurs in China.