Plasmid for tetracycline resistance in Staphylococcus epidermidis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Plasmids are extrachromosomal DNA elements that can confer antibiotic resistance.
• Staphylococcus epidermidis is a common bacterium that can cause infections.

Purpose of the Study:

• To characterize a tetracycline resistance plasmid in Staphylococcus epidermidis.
• To investigate the stability and transferability of this plasmid.

Main Methods:

• Spontaneous loss experiments at different temperatures and in the presence of ethyl violet.
• Transduction experiments with ultraviolet-irradiated phage.
• Isolation and characterization of plasmid DNA using CsCl-ethidium bromide gradients and sucrose gradient centrifugation.

Main Results:

• Tetracycline resistance was spontaneously lost at a low frequency (<0.1 to 1.3%) and was not enhanced by heat or ethyl violet.
• Transduction rate decreased with increased ultraviolet irradiation of the phage.
• Plasmids from S. aureus and S. epidermidis with tetracycline resistance had similar molecular weights.
• An extrachromosomal element in the recipient strain lost integrity in alkaline sucrose gradients.

Conclusions:

• The tetracycline resistance in S. epidermidis is plasmid-mediated.
• The plasmid appears to be stably maintained and its transfer can be affected by phage irradiation.
• The molecular weight of the tetracycline resistance plasmid is similar to that found in S. aureus.