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Updated: Jan 28, 2026
Scalable Isolation and Purification of Extracellular Vesicles from Escherichia coli and Other Bacteria
Published on: October 13, 2021
Antimicrobial resistance-encoding plasmid clusters with heterogeneous MDR regions driven by IS26 in a single
Dan Dan He1, Shi Yu Zhao1, Hua Wu1
1College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, China.
Background:
IS26-flanked transposons played an increasingly important part in the mobilization and development of resistance determinants. Heterogeneous resistance-encoding plasmid clusters with polymorphic MDR regions (MRRs) conferred by IS26 in an individual Escherichia coli isolate have not yet been detected.
Objectives:
To characterize the complete sequence of a novel blaCTX-M-65- and fosA3-carrying IncZ-7 plasmid with dynamic MRRs from an E. coli isolate, and to depict the mechanism underlying the spread of resistance determinants and genetic polymorphisms.
Methods:
The molecular characterization of a strain carrying blaCTX-M-65 and fosA3 was analysed by antimicrobial susceptibility testing and MLST. The transferability of a plasmid bearing blaCTX-M-65 and fosA3 was determined by conjugation assays, and the complete structure of the plasmid was obtained by Illumina, PacBio and conventional PCR mapping, respectively. The circular forms derived from IS26-flanked transposons were detected by reverse PCR and sequencing.
Results:
A novel IncZ-7 plasmid pEC013 (∼118kb) harbouring the blaCTX-M-65 and fosA3 genes was recovered from E. coli isolate EC013 belonging to D-ST117. The plasmid was found to have heterogeneous and dynamic MRRs in an individual strain and the IS26-flanked composite transposon-derived circular intermediates were identified and characterized in pEC013.
Conclusions:
The heterogeneous MRRs suggested that a single plasmid may actually be a cluster of plasmids with the same backbone but varied MRRs, reflecting the plasmid's heterogeneity and the survival benefits of having a response to antimicrobial-related threatening conditions in an individual strain.
Insights
IS26-flanked transposons drive antimicrobial resistance. Researchers discovered a novel plasmid in Escherichia coli with dynamic, heterogeneous resistance regions, suggesting a cluster of plasmids within a single strain for enhanced survival.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- IS26-flanked transposons are crucial for mobilizing antimicrobial resistance genes.
- Previously, heterogeneous resistance-encoding plasmid clusters with polymorphic MDR regions (MRRs) in individual Escherichia coli isolates were not identified.
Purpose of the Study:
- To fully sequence a new IncZ-7 plasmid carrying blaCTX-M-65 and fosA3 genes.
- To investigate the mechanisms behind the spread of resistance and genetic variations in these plasmids.
Main Methods:
- Antimicrobial susceptibility testing and MLST were used for molecular characterization.
- Conjugation assays determined plasmid transferability.
- Illumina, PacBio sequencing, and PCR mapping elucidated the complete plasmid structure.
- Reverse PCR and sequencing identified IS26-flanked transposon-derived circular forms.
Main Results:
- A novel IncZ-7 plasmid, pEC013 (approx. 118kb), containing blaCTX-M-65 and fosA3, was isolated from Escherichia coli EC013 (D-ST117).
- This plasmid exhibited heterogeneous and dynamic MRRs within the individual strain.
- IS26-flanked composite transposon-derived circular intermediates were identified and characterized.
Conclusions:
- The findings suggest that a single plasmid can represent a cluster of plasmids with shared backbones but diverse MRRs.
- This heterogeneity likely enhances bacterial survival by providing adaptive responses to antimicrobial threats.
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