Background:Trichomoniasis is a disease caused by the parasitic protozoan flagellate Trichomonas vaginalis. It is considered the most common non-viral sexually transmitted disease in the world. Metronidazole is the drug of choice in treatment of trichomoniasis. Side effects of Metronidazole and its resistance are the main causes for finding new alternatives for trichomoniasis treatment. The present study is concerned with evaluation of the effect of different concentrations of Nigella sativa oil at different durations in the treatment of T.vaginalis and comparison of their efficacy with Metronidazole under in vitro conditions of axenic culture of isolated T.vaginalis trophozoites.
Materials and Methods: Vaginal samples were collected from ninety female patients complaining of characteristic vaginal discharge or other manifestations of trichomoniasis. Vaginal swabs of infected females were examined microscopically for motile trophozoites. Then they were axenically cultured on modified Diamond's medium. The effect of Nigella sativa oil at different concentrations (500, 750, 1000μg/ml) on Trichomonas vaginalis was measured by counting number of dead trophozoites using haemocytometer and trypan blue staining. The effect of Nigella sativa oil on ultrastructure of the parasite was determined by transmission electron microscope.

Results: Nigella sativa oil showed high toxic effect on the parasite as it causes severe cell damage with cytoplasmic and nuclear destruction.
Conclusions: Nigella sativa oil has antitrichomonal effect in vitro at different concentrations and different durations as well as it has low toxicity and low side effects. So, it can be a good alternative for metronidazole in treatment of Trichomoniasis.