RIBOSOMES FROM AN OXAZOLIDINONE-RESISTANT MUTANT CONFER RESISTANCE TOEPEREZOLID IN A STAPHYLOCOCCUS-AUREUS CELL-FREE TRANSCRIPTION-TRANSLATION ASSAY

Oxazolidinone-resistant mutants of Staphylococcus aureus, isolated wit h a spiral plating technique, had a 16-fold higher MIC (2 versus 32 mu g/ml) of eperezolid when compared to the parental sensitive strain. E perezolid inhibited in vitro protein translation with 50% inhibitory c oncentrations of 30 mu M for the oxazolidinone-sensitive S30 extract a nd 75 mu M for the resistant extract. Experiments mixing various combi nations of S100 and crude ribosome preparations from oxazolidinone-sen sitive and -resistant S. aureus strains in a transcription-translation assay demonstrated that the resistant determinant resided within the ribosomal fraction. Ribosomes from the oxazolidinone-resistant strain bound less drug than ribosomes from the sensitive strain, indicating t hat the ribosome is the site of action for the oxazolidinones. These e xperiments demonstrate that an alteration of the ribosome is responsib le for some or all of the oxazolidinone resistance observed in the S. aureus mutant.