Inducible resistance to a 16-membered macrolide, mycinamicin, in Staphylococcus aureus resistant to 14-membered macrolides and streptogramin B antibiotics.

Staphylococcus aureus 8325(pEP2104), a transductant derived from S. aureus PM2104 isolated clinically in Hungary (L. Janosi, and E. Ban, Acta Microbiol. Acad. Sci. Hung., 29: 187-200, 1982), exhibited an inducible resistance to the 14-membered macrolides [erythromycin (EM) and oleandomycin (OL)] and streptogramin B (MKM-B) antibiotics, but not to the 16-membered macrolides and lincosamides. This resistance was referred to as PMS-resistance phenotype (L. Jánosi, Y. Nakajima, and H. Hashimoto, Microbiol. Immunol., 34: 723-735, 1990). In addition to EM, OL, and MKM-B, however, the strain was recently and first observed to have inducible resistance to mycinamicin, a 16-membered ring macrolide. Thereby, we propose that the reference stated just above as PMS-resistance has to be extended to such 16-membered macrolides as mycinamicin. An optimum concentration of erythromycin or oleandomycin for induction of PMS-resistance was 1.35 mu g/ml in the strain 8325(pEP2104). The concentration was about 30 times as great as that (0.05 mu g/ml) required for induction of well-known co-resistance to macrolide-lincosamide-streptogramin B antibiotics in S. aureus ISP447.