Localization of genes coding for macrolide resistance on the penicillinase plasmid of isolates of an epidemic Staphylococcus aureus.

Genetic localization of gene(s) coding for erythromycin and oleandomycin resistance in five isolates of phage complex 52, 52A, 80, 81, multiple antibiotic resistant epidemic Staphylococcus aureus was studied. The 100% coelimination rate of erythromycin, oleandomycin, penicillin (penicillinase production) and certain heavy metal ion resistances from each of the clinical isolates and the 100% cotransduction rate of these resistance markers from two clinical isolates as well as changes in the partially purified extrachromosomal DNA patterns of the clinical wild types after elimination and the recipients after transduction indicated that erythromycin and oleandomycin resistance determining gene(s) resided on the penicillinase-heavy metal ion resistance plasmid in each of the isolates. The electrophoretic mobility of these macrolide-penicillinase-heavy metal ion resistance plasmids (MacPc plasmids) was the same in four strains and higher in one strain. These MacPc plasmids did not confer any resistance to spiramycin and lincomycin (even after induction) or to kanamycin, which features differentiate them from MacPc plasmids pI 258 and pTU 512 formerly identified in Staphylococcus aureus in Japan.