New plasmid (pTU512), mediating resistance to penicillin, erythromycin, and kanamycin, from clinical isolates of Staphylococcus aureus.

Multiply drug-resistant strains of Staphylococcus aureus were isolated from pediatric patients with severe staphylococcal infections in 1974 through 1976. Resistance to benzylpenicillin, erythromycin, and kanamycin was jointly eliminated without exception from these multiply drug-resistant strains by treatment with ethidium bromide. It was also found that the triple drug resistance in a representative strain, TK512-200, was always transduced to a susceptible strain simultaneously. Moreover, a single class of plasmid deoxyribonucleic acid was isolated from a transductant and found to be 14.4 +/- 0.6 mum in length, with a molecular weight corresponding to 29.8 x 10(6). From these results, it is concluded that the plasmid (pTU512) is a new one, mediating resistance to penicillin, erythromycin, and kanamycin.