Characteristics and localization of a determinant conferring partial macrolide resistance in Staphylococcus aureus carrying plasmid.

Staphylococcus aureus TPR-27, a clinically isolated strain, showed constitutive resistance to some macrolide antibiotics (erythromycin, oleandomycin, spiramycin, and josamycin), but susceptibility to the other macrolide (tylosin, rokitamycin, and mycinamicin), lincosamide, and streptogramin type B antibiotics (PM-resistance). The PM-resistant strain TPR-27 has carried for visible plasmids. Attempts to eliminate the resistant determinant in terms of ethidium bromide (about 3 micrograms/ml) did not succeed, and every trial to transduce the PM-resistant determinant into rec- mutant ISP105 using phage 80L2 propagated on strain TPR-27 also failed at the frequency of less than 1.1 x 10(-10) transductants per plaque-forming unit. These results suggest that the PM-resistance determinant is localized in chromosomal DNA.