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Plasmids of Pseudomonas cepacia strains of diverse origins
1Department of Biology, Catholic University of America, Washington, D.C. 20064.
Abstract:
Thirty-seven strains of Pseudomonas cepacia from clinical, pharmaceutical-industrial, and environmental origins were analyzed for the presence of plasmid DNA by a modification of the rapid alkaline extraction method of Birnboim (H. C. Birnboim, Methods Enzymol. 100:243-255, 1983). Plasmids were present in 31 strains (84%) from all sources, with no one source showing less than 75% plasmid carriage among its strains. The plasmid profiles indicated that the presence of large plasmids (146 to 222 kb) was the norm. Those strains with greater antibiotic resistance were mainly in the clinical and pharmaceutical groups and carried large plasmids (222 kb) that appeared essentially identical by restriction digest analysis. The ability for conjugative transfer was shown with the broad-host-range plasmid R751 carrying the gene for resistance to trimethoprim, one of the few antimicrobial agents effective against P. cepacia. The plasmid was transferred from Pseudomonas aeruginosa to P. cepacia strains as well as from P. cepacia transconjugants to other P. cepacia strains.
Insights
Most Pseudomonas cepacia strains carry large plasmids, which are linked to antibiotic resistance. These plasmids can be transferred between strains, impacting treatment options for P. cepacia infections.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Pseudomonas cepacia is an opportunistic pathogen.
- Antibiotic resistance in P. cepacia poses a significant clinical challenge.
- Plasmids are known to contribute to antibiotic resistance.
Purpose of the Study:
- To investigate the prevalence and characteristics of plasmid DNA in Pseudomonas cepacia strains.
- To correlate plasmid presence and size with antibiotic resistance.
- To assess the transferability of plasmids within P. cepacia.
Main Methods:
- Modified alkaline extraction method for plasmid DNA isolation.
- Restriction digest analysis for plasmid characterization.
- Conjugative transfer experiments using a known plasmid (R751).
Main Results:
- Plasmids were detected in 84% of the analyzed P. cepacia strains from diverse origins.
- Large plasmids (146-222 kb) were common, with 222 kb plasmids frequently found in resistant clinical and pharmaceutical strains.
- Conjugative transfer of trimethoprim resistance via plasmid R751 was demonstrated between P. cepacia strains and from P. aeruginosa to P. cepacia.
Conclusions:
- Plasmids are a common feature of P. cepacia, often large and associated with antibiotic resistance.
- The conjugative transfer of resistance plasmids contributes to the spread of antibiotic resistance in P. cepacia populations.
- Understanding plasmid dynamics is crucial for managing P. cepacia infections.