INDUCIBLE RESISTANCE TO ERYTHROMYCIN IN STAPHYLOCOCCUS AUREUS

Abstract

The dissociated resistance of S. aureus to erythromycin was examined and was found to possess the characteristics of an inducible enzyme. The induction of resistance to high concentrations of erythromycin in S. aureus occurred only after prior exposure to subin-hibitory concentrations of erythromycin. The only macrolide antibiotic examined which induced resistance was erythromycin, and the resistance of induced populations was rapidly lost when they were grown in the absence of this antibiotic. Induction did not occur when protein synthesis was inhibited by either chloramphenicol or histidine starvation of a histidine auxotroph. The macrolide antibiotics inhibited the induction of resistance at the same minimal concentrations required to inhibit growth and induced synthesis of [beta]-galactosidase. Therefore, the mode of action of the macrolide antibiotics is to inhibit protein synthesis, and the induction of resistance overcomes this inhibition in some manner which is associated with the synthesis of new protein.