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Comparison of enterococcal and staphylococcal beta-lactamase-encoding fragments
1Center for Infectious Diseases, University of Texas Medical School, Houston 77030.
Antimicrobial Agents and Chemotherapy
|February 1, 1992
Summary
Beta-lactamase-encoding plasmids in enterococci show significant genetic variation. Restriction mapping reveals differences in plasmid DNA, even within the same bacterial strain, impacting beta-lactamase gene structure.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Beta-lactamase enzymes confer antibiotic resistance.
- Plasmids are key mobile genetic elements carrying resistance genes.
- Enterococcal and staphylococcal plasmids are important in clinical settings.
Purpose of the Study:
- To investigate the genetic variability of beta-lactamase-encoding plasmids in enterococci.
- To compare plasmid structures from different geographic isolates.
- To determine the conservation of the beta-lactamase structural gene (blaZ).
Main Methods:
- Restriction mapping of EcoRI and EcoRV fragments.
- Analysis of plasmid DNA from enterococcal and staphylococcal strains.
- Comparison of restriction sites within the beta-lactamase gene.
Main Results:
- The 13.5-kb EcoRI fragment from enterococcal strain PA differed from staphylococcal plasmids and strain HH22.
- EcoRV fragment sizes encompassing the beta-lactamase gene varied among strains.
- Restriction sites within the blaZ gene were conserved across all studied plasmids.
- Geographic isolates showed distinct EcoRV fragment patterns, correlating with PA or HH22/staphylococcal types.
Conclusions:
- Significant plasmid diversity exists for beta-lactamase genes in enterococci.
- While the blaZ gene is conserved, surrounding plasmid regions exhibit variation.
- This variation may reflect different plasmid lineages or evolutionary events in enterococci.