In vitro effect of metronidazole on the ultrastructure of Trichomonas vaginalis donné.

The effect of metronidazole on the growth and fine structure of exponeentially growing cells of Trichomonas vaginalis was examined. Cell division stopped about one hour after the addition of 1-4 mug/ml of metronidazole, and the cells were apparently arrested in the interphase. One to two hours after the addition of metronidazole, the movement of flagella and of the undulating membrane had decreased, but cell death had not occurred until 7-8 hours later. The fine structure of the cytoplasm was changed 30 to 60 minutes after addition of metronidazole. Proportionally, the number of polyribosomes had decreased whereas the number of single ribosomes in the cytoplasm had increased. The electron-density of the cytoplasmic matrix was higher in cells which were treated with metronidazole than in cells from control cultures. The findings of the present study indicate that the initial effect of metronidazole on T. vag. cells in vitro is an inhibition of cell multiplication as well as an impairment of protein synthesis.