Interspecific relationships of antibiotic resistance in Staphylococcus sp.: isolation and comparison of plasmids determining tetracycline resistance in S. aureus and S. epidermidis

Tetracycline resistance in Staphylococcus aureus and S. epidermidis was confirmed to be determined by plasmids of the same size. Digestion of plasmids from each strain with restriction endonucleases EcoR1, HindIII, and AluI showed a high degree of similarity in their DNA sequences. At least 10 cleavage sites which appear to be common to both plasmids were detected. An additional three cleavage sites appear to be unique to the S. epidermidis plasmid. Further, a survey of recent clinical isolates of tetracycline-resistant staphylococci detected 7 or 10 S. aureus strains and 8 of 9 S. epidermidis strains with plasmids which were of similar size to the purified reference plasmids and which, by hybridization, showed extensive DNA homology to the S. aureus reference plasmid DNA.