Comparison of enterococcal and staphylococcal beta-lactamase plasmids

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Beta-lactamase (Bla) genes in Staphylococcus aureus are often found on transducible plasmids encoding metal resistance or conjugative gentamicin resistance plasmids.
• The beta-lactamase gene in Enterococcus faecalis shares homology with S. aureus bla and is also located on conjugative, gentamicin resistance plasmids.

Purpose of the Study:

• To investigate the similarity between Bla-encoding plasmids from S. aureus and E. faecalis.
• To determine if enterococcal Bla-encoding plasmids share common origins or structures with staphylococcal plasmids.

Main Methods:

• Comparison of Bla-encoding plasmids from both bacterial species using restriction endonuclease digestion.
• Hybridization assays utilizing Bla and gentamicin resistance gene probes, and an enterococcal Bla-encoding plasmid probe.

Main Results:

• Staphylococcal plasmids exhibited distinct restriction patterns, differentiating transducible from conjugative types.
• Enterococcal plasmids showed considerable similarity to each other but not to the staphylococcal plasmid restriction patterns.
• Limited similarity was observed between staphylococcal and enterococcal plasmids, primarily concerning the bla and gentamicin resistance genes.

Conclusions:

• Bla-encoding plasmids in E. faecalis appear structurally distinct from those commonly found in S. aureus.
• The acquisition of the bla gene in enterococci may involve a different plasmid type or horizontal gene transfer mechanisms like transposition or recombination.