FIG. 4.

Effect of Erm induction on whole-cell drug accumulation and cell protein synthesis. (A) Accumulation of macrolide or ketolide in S. pneumoniae 5970 with or without induction of ErmB methylase by erythromycin. Cells were grown for several generations with or without 0.2 μg of erythromycin per ml at 37°C in growth medium prior to centrifugation and resuspension in Miller's M9 medium at 3.8 × 10⁹ CFU/ml. Cells were then incubated at 23°C with either 0.2 or 0.6 μg of [¹⁴C]erythromycin (gray bars) or [¹⁴C]ABT-773 (black bars) per ml for 20 min. Labeled cells were processed as outlined in Materials and Methods. Results are presented as means ± standard deviations (error bars) (n = 3). (B) S-30 extracts prepared from S. pneumoniae 5970 before and after Erm induction were run in the transcription-translation assay outlined in Materials and Methods. Erythromycin (gray bars) and ABT-773 (black bars) were tested at 100 μM. Results were expressed as percent inhibition with or without induction.