Abstract
SUMMARY: In four out of five strains of Staphylococcus aureus examined, genes determining fusidic acid resistance were associated with a penicillinase plasmid. In one strain (FAR5), although the linkage was unstable, resistance to fusidic acid was co-transduced with resistance to cadmium ions and penicillinase production. Further evidence for a single plasmid in this strain was obtained by studying the physical nature of the plasmid DNA. The molecular weight of the entire linkage group was about 16 million daltons; the molecular weight of the residual plasmid after loss of fusidic acid resistance was about 15 million.