Genetic Characterization of bla NDM-1-Carrying Citrobacter portucalensis Sequence Type 328 and Citrobacter freundii Sequence Type 98
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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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