Effect of metronidazole on the cell surface charge of Trichomonas vaginalis and Tritrichomonas foetus.

1. The effect of metronidazole, a drug used in the treatment of trichomoniasis, on the surface charge of both Trichomonas vaginalis and Tritichomonas foetus was analyzed by cell electrophoresis. 2. Incubation of the parasites under anaerobic conditions for 2 or 120 min in the presence of 2.0 micrograms/ml metronidazole, a concentration which inhibits cell growth by about 50%, led to a marked decrease in the net surface charge of the parasites. 3. The metronidazole analogue, 1-hydroxyethyl-2-methyl-1-4-nitroimidazole, inhibited protozoan growth but had no effect on net surface charge. 4. These observations indicate that, in addition to its effect on intracellular structure, such as hydrogenosomes, metronidazole alters the surface of trichomonads.