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Published on: May 29, 2016
Novel IncR/IncP6 Hybrid Plasmid pCRE3-KPC Recovered from a Clinical KPC-2-Producing Citrobacter braakii Isolate
Dandan Dong1, Ziqiang Mi2, Dujun Li3
1Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, China.
Abstract:
Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae have become widespread in hospitals and the environment. Here, we describe a blaKPC-2-carrying plasmid called pCRE3-KPC, which was recovered from a clinical multidrug-resistant Citrobacter braakii CRE3 strain in China. The complete nucleotide sequence of pCRE3-KPC was determined by combining MiSeq and MinION sequencing and then compared with those of three related plasmids. Plasmid conjugal transfer and electroporation tests, modified carbapenem inactivation method, and bacterial antimicrobial susceptibility test were carried out. We compared this plasmid with three related plasmids to verify that the backbone of pCRE3-KPC was composed of the backbones of the IncR plasmid and IncP6 plasmid. Further bioinformatics analysis showed that pCRE3-KPC carried two resistance-related regions (the blaKPC-2 gene cluster and the aacC2-tmrB-related region). The aacC2-tmrB-related region included two novel insertion sequences (ISCfr28 and ISCfr16).IMPORTANCE Reports of human-pathogenic C. braakii strains, especially of strains showing resistance to carbapenems, are rare. To the best of our knowledge, our results represent the first detection of carbapenemase gene blaKPC-2 in C. braakii strains. In addition, we have studied detailed genetic characteristics of the novel IncR/IncP6 hybrid plasmid pCRE3-KPC, which was isolated from a clinical multidrug-resistant Citrobacter braakii CRE3 strain. Our results may provide further insight into the horizontal transfer of multidrug resistance genes in bacteria and into the genomic diversity and molecular evolution of plasmids.
Insights
This study identifies the first carbapenemase gene blaKPC-2 in a multidrug-resistant Citrobacter braakii strain. The novel hybrid plasmid pCRE3-KPC sheds light on antimicrobial resistance gene transfer in bacteria.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are a growing global health concern in clinical settings.
- Carbapenem-resistant Citrobacter braakii strains are infrequently reported, making their resistance mechanisms poorly understood.
Purpose of the Study:
- To characterize the novel blaKPC-2-carrying plasmid, pCRE3-KPC, isolated from a multidrug-resistant Citrobacter braakii strain.
- To investigate the genetic features and potential for horizontal gene transfer of this plasmid.
Main Methods:
- Whole-genome sequencing using MiSeq and MinION technologies.
- Plasmid conjugation, electroporation, and antimicrobial susceptibility testing.
- Bioinformatic analysis for plasmid backbone and resistance gene region identification.
Main Results:
- The blaKPC-2 gene was identified in a clinical multidrug-resistant Citrobacter braakii strain (CRE3) in China.
- A novel IncR/IncP6 hybrid plasmid, pCRE3-KPC, carrying blaKPC-2 was fully sequenced and characterized.
- The plasmid backbone is a hybrid of IncR and IncP6 plasmids, containing two resistance regions, including novel insertion sequences IS Cfr28 and IS Cfr16.
Conclusions:
- This is the first report of the blaKPC-2 gene in Citrobacter braakii, highlighting a new challenge in combating carbapenem resistance.
- The characterization of the pCRE3-KPC plasmid provides insights into plasmid evolution and the mechanisms of multidrug resistance gene dissemination.
