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Updated: May 11, 2026
Replication of the Ordered, Nonredundant Library of Pseudomonas aeruginosa strain PA14 Transposon Insertion Mutants
Published on: May 4, 2018
Complete sequence of pOZ176, a 500-kilobase IncP-2 plasmid encoding IMP-9-mediated carbapenem resistance, from
Jianhui Xiong1, David C Alexander, Jennifer H Ma
1Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
Abstract:
Pseudomonas aeruginosa 96 (PA96) was isolated during a multicenter surveillance study in Guangzhou, China, in 2000. Whole-genome sequencing of this outbreak strain facilitated analysis of its IncP-2 carbapenem-resistant plasmid, pOZ176. The plasmid had a length of 500,839 bp and an average percent G+C content of 57%. Of the 618 predicted open reading frames, 65% encode hypothetical proteins. The pOZ176 backbone is not closely related to any plasmids thus far sequenced, but some similarity to pQBR103 of Pseudomonas fluorescens SBW25 was observed. Two multiresistant class 1 integrons and several insertion sequences were identified. The blaIMP-9-carrying integron contained aacA4 → bla(IMP-9) → aacA4, flanked upstream by Tn21 tnpMRA and downstream by a complete tni operon of Tn402 and a mer module, named Tn6016. The second integron carried aacA4 → catB8a → bla(OXA-10) and was flanked by Tn1403-like tnpRA and a sul1-type 3' conserved sequence (3'-CS), named Tn6217. Other features include three resistance genes similar to those of Tn5, a tellurite resistance operon, and two pil operons. The replication and maintenance systems exhibit similarity to a genomic island of Ralstonia solanacearum GM1000. Codon usage analysis suggests the recent acquisition of bla(IMP-9). The origins of the integrons on pOZ176 indicated separate horizontal gene transfer events driven by antibiotic selection. The novel mosaic structure of pOZ176 suggests that it is derived from environmental bacteria.
Insights
This study analyzed the carbapenem-resistant plasmid pOZ176 from Pseudomonas aeruginosa. Its novel mosaic structure, containing multiple resistance genes and integrons, suggests origins from environmental bacteria and highlights horizontal gene transfer driven by antibiotic selection.
Area of Science:
- Microbiology
- Genomics
- Antimicrobial Resistance
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen.
- Carbapenem resistance in P. aeruginosa is a growing global health concern.
- Understanding the genetic basis of resistance is crucial for effective treatment strategies.
Purpose of the Study:
- To characterize the IncP-2 carbapenem-resistant plasmid, pOZ176, from a P. aeruginosa outbreak strain.
- To investigate the genetic elements contributing to multidrug resistance.
- To elucidate the evolutionary origins and acquisition mechanisms of resistance genes.
Main Methods:
- Whole-genome sequencing of the P. aeruginosa strain PA96.
- Bioinformatic analysis of the plasmid pOZ176 genome.
- Identification and characterization of resistance genes, integrons, and mobile genetic elements.
- Comparative genomics to assess plasmid backbone similarity and origins.
Main Results:
- The 500,839 bp plasmid pOZ176 harbors two multidrug-resistant class 1 integrons and multiple resistance genes, including blaIMP-9, aacA4, blaOXA-10, and tellurite resistance.
- The plasmid backbone shows limited similarity to known plasmids but shares features with a genomic island of Ralstonia solanacearum.
- Novel composite mobile genetic elements, Tn6016 and Tn6217, were identified, carrying resistance genes and integrons.
- Codon usage analysis indicates recent acquisition of the blaIMP-9 gene.
Conclusions:
- The plasmid pOZ176 possesses a unique mosaic structure, indicative of derivation from environmental bacteria.
- The presence of multiple integrons and resistance genes highlights the role of horizontal gene transfer in the dissemination of carbapenem resistance.
- Antibiotic selection likely drove the acquisition and integration of these resistance elements.
- This study provides insights into the evolution and spread of carbapenem resistance in Pseudomonas aeruginosa.
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