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Genetic Characterization of bla NDM-1-Carrying Citrobacter portucalensis Sequence Type 328 and Citrobacter freundii
Lijun Wang1, Ziyao Li2, Nan Xiao1
1Department of Clinical Laboratory, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, Beijing, 102218, People's Republic of China.
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.
Insights
This study identified novel plasmids carrying the New Delhi metallo-beta-lactamase 1 (NDM-1) gene in Citrobacter bacteria. These findings highlight potential horizontal gene transfer contributing to antibiotic resistance in hospital settings.
Area of Science:
- Medical Microbiology
- Genomics
- Antimicrobial Resistance
Background:
- The emergence of carbapenemase-producing Enterobacteriaceae poses a significant global health threat.
- NDM-1 is a critical carbapenemase enzyme frequently associated with multidrug resistance.
- Co-occurrence of different NDM-1 producing bacteria in clinical settings necessitates detailed molecular characterization.
Purpose of the Study:
- To characterize the plasmids carrying the blaNDM-1 gene in co-occurring Citrobacter portucalensis and Citrobacter freundii strains.
- To investigate the genetic features of these NDM-1-carrying plasmids.
- To understand the potential for horizontal gene transfer of NDM-1.
Main Methods:
- Bacterial identification using MALDI-TOF mass spectrometry.
- Antibiotic susceptibility testing with VITEK® 2 compact system.
- Whole-genome sequencing (WGS) using Illumina and QNome platforms.
Main Results:
- Citrobacter portucalensis strain Cf7303 (ST328) harbored a novel IncFIB plasmid (pNDM-Cf7303) with multiple antibiotic resistance genes, including blaNDM-1.
- Citrobacter freundii strains Cf7308 and Cf7313 (ST98) carried an IncN1 plasmid (pNDM-Cf7308) homologous to other NDM-1 plasmids.
- The study identified a diverse array of antibiotic resistance genes on the characterized plasmids.
Conclusions:
- A novel IncFIB plasmid carrying blaNDM-1 was characterized in Citrobacter portucalensis.
- Closely related IncN1 plasmids carrying blaNDM-1 were found in Citrobacter freundii.
- The findings suggest interspecies or intraspecies horizontal transfer of NDM-1 carrying plasmids within hospital environments.
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