Antibiotic resistance and plasmids in Staphylococcus aureus from normal populations.

Antibiotic resistance, plasmid profiles and plasmid structures were examined in nasal Staphylococcus aureus collected from a random sample of normal individuals in the mid 1960s and from women at an antenatal clinic in 1989. The results were generally similar except for an increase in the resistance to penicillin in the later sample. The plasmid population had changed little though more uncategorized plasmids were evident in the 1960s samples.