Variation in the prevalence of antibiotic resistance of Staphylococcus aureus from human skin and nares.

Patients whose skins are colonized with Staphylococcus aureus resistant to penicillin and/or tetracycline may carry variants that are sensitive to these antibiotics. The skin of most individuals yields the fully resistant type as the predominant flora and the nose harbours the sensitive version. This probably represents plasmid loss in vivo. The plasmid-positive cells were not more resistant to desiccation or more deeply pigmented than plasmid-negative cells. The explanation for such distributions is unknown.