Fig. 5
Related macrolides inhibit merozoite invasion. The 14-membered macrolides (a) erythromycin A (IC50 mero 420 μM), (b) roxithromycin (83 μM), (c) dirithromycin (521 μM) and (d) the 16-membered macrolide spiramycin (123 μM) had variable levels of invasion inhibitory activity (green) and a higher IC50 than that achieved for 1 cycle assays (red). (e) The invasion inhibitory activity of erythromycin A, roxithromycin and spiramycin at an IC80 concentration was confirmed by flow cytometry assessment of ring stages with minimal inhibition evident for pretreated erythrocytes. All experiments represent the mean and SEM of three or more experiments. Significance of differences was compared using an unpaired t-test (**P ≤0.01, ***P ≤0.001)