Physical studies of a Staphylococcus aureus plasmid mediating resistance to streptogramins, lincosamins and aminoglycosides.

Previous studies have demonstrated that resistance to three groups of drugs (streptogramins, lincosamins and aminoglycosides) was plasmid borne in a clinical isolate of Staphylococcus aureus. This plasmid, referred to as pIP524, was transferred in mixed culture or transduced into a plasmid-free host and analyzed for size, molecular weight and replication control. Plasmid pIP524 is a new member of the class of "large" plasmids (8.5 micrometer) isolated from S. aureus and represents up to 7% of total DNA. Some evidence indicates that the number of copies of pIP524 and of plasmids of the same size--penicillinase plasmids--are similar (up to 10 per cell).