CHARACTERISTICS AND LOCALIZATION OF A DETERMINANT CONFERRING PARTIAL MACROLIDE RESISTANCE IN STAPHYLOCOCCUS-AUREUS CARRYING PLASMID

Staphylococcus aureus TPR-27, a clinically isolated strain, showed con stitutive resistance to some macrolide antibiotics (erythromycin, olea ndomycin, spiramycin, and josamycin), but susceptibility to the other macrolide (tylosin, rokitamycin, and mycinamicin), lincosamide, and st reptogramin type B antibiotics (PM-resistance). The PM-resistant strai n TPR-27 has carried for visible plasmids. Attempts to eliminate the r esistant determinant in terms of ethidium bromide (about 3 mug/ml) did not succeed, and every trial to transduce the PM-resistant determinan t 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.