FIG 4.

Relationship of drug treatment to B. mandrillaris encystment. (A to D) Changes in the number of trophozoites (blue) and cysts (red) in B. mandrillaris populations following 72 h of treatment with various concentrations of nitroxoline (A), pentamidine isethionate (B), miltefosine (C), and azithromycin (D). Low micromolar concentrations of nitroxoline and pentamidine isethionate caused an increase in the total number of cysts observed in B. mandrillaris populations and an increase in the ratio of cysts to trophozoites. No increase in encystment was observed in B. mandrillaris populations treated with miltefosine or azithromycin. (E) Dose-response curve showing the effect of nitroxoline (red), pentamidine isethionate (black), miltefosine (blue), and azithromycin (gray) on the viability of preformed B. mandrillaris cysts. Nitroxoline was the most potent inhibitor of cysts, with an IC₅₀ of 15.48 µM. Cysts were substantially less sensitive than trophozoites (Fig. 2A) to all drugs except for miltefosine, which had similar IC₅₀ values for inhibition of both B. mandrillaris forms.