Detection of an integrated tetracycline resistance plasmid in the chromosome of methicillin-resistant Staphylococcus aureus.

The majority of multiresistant Staphylococcus aureus strains isolated in Australian hospitals since 1970 carry a chromosomally-encoded minocycline and tetracycline resistance determinant. By using DNA-DNA hybridization, some of these multiresistant strains were shown to possess also a tetracycline resistance plasmid, equivalent to pT181, integrated into a unique site in the chromosome. By relating the hybridization data to the map of pT181, the site of integration on this plasmid was established to be between the genes for replication and tetracycline resistance.