FIG 1.

Effect of macrolides and lincosamide on the proliferation and hemolytic activity of macrolide-resistant S. pneumoniae (MRSP). (A) MRSP strain NU4471 was inoculated in TS broth and cultured with various concentrations of CLI, CLR, and ROX for 18 h at 37°C. The optical density (OD) of each well was measured at 600 nm. The data represent the mean ± SD of triplicate experiments. (B and C) MRSP strain NU4471 was cultured in the presence or absence of 5 μg/ml CLI, CLR, ERY, or ROX at 37°C. (B) The OD of each sample was measured at 600 nm at various time points. The data represent the mean ± SD of triplicate experiments and were evaluated using two-way analysis of variance with Tukey’s multiple-comparison test. *, Significantly different compared with all other antibiotic-treated groups at P < 0.05. (C) The hemolytic activity of each cell-free supernatant was determined. Supernatants from S. pneumoniae wild-type strain D39 and the ply isogenic mutant (Δply) were used as controls. The data represent the mean ± SD of quadruplicate experiments and were evaluated using one-way analysis of variance with Tukey’s multiple-comparison test. †, Significantly different compared to the control at P < 0.05. *, Significant difference between the indicated groups at P < 0.05. CLI, clindamycin; CLR, clarithromycin; Ctrl, control; ERY, erythromycin; MRSP, macrolide-resistant Streptococcus pneumoniae; ND, not detected; OD, optical density; ROX, roxithromycin; SD, standard deviation; TS, tryptic soy.