Growth inhibition of Leishmania tropica amastigotes in vitro by rifampicin combined with amphotericin B

Rifampicin and amphotericin B (AMB) were studied separately and in combination to determine their effect in vitro on intracellular Leishmania tropica amastigotes. On the fourth day of treatment, rifampicin at 200 μg ml^-1 or AMB at 0.15 μg ml^-1 reduced the parasites' survival index (PSI) to 10% compared with the untreated control. In combination, there was a significant synergistic effect at several concentrations. The synergistic therapeutic effects were not accompanied by toxicity to the host cells, although each drug alone caused cellular degeneration in the ultrastructure of the parasites with the formation of large autophagic-like vacuoles, while the combination increased the percentage of degenerate cells.