Abstract: Objective To study the influence of iron ion on the growth of Trichomonas vaginalis in vitro. Methods Quantitative pure incubation of T. vaginalis trophozoites with an initial density of 1×105/ml was carried out at 37 ℃ in TYM （trypticase-yeast extract-maltose） medium （pH 6.0） with additional 100, 200, 300, and 400 μmol/L iron ion, respectively, and in TYM medium without additional iron ion as control. The numbers of live and dead trichomonads were counted under an optical microscope after trypan blue staining, and the growth curve and survival rate of T. vaginalis were drawn to calculate the generation time of T. vaginalis. The minimal lethal concentration （MLC） of metronidazole was tested by serial dilution method when the trophozoites of T. vaginalis were incubated in TYM medium with 200 μmol/L iron ion and in control group without additional iron ion. Results The maximum densities of 2.9×106, 3.2×106, 3.1×106, and 2.8×106/ml were obtained when the trophozoites were incubated for 40 h in TYM medium with 100, 200, 300, and 400 μmol/L iron ion, respectively, while the maximum density was achieved at 50 h in the control, which was 2.5×106/ml. The generation time was （6.8±0.7） h in 400 μmol/L iron ion group, longer than those in the groups with 100-300 μmol/L iron ion, which were （4.8±0.3）, （4.8±0.2）, and （5.0±0.4） h, respectively （P﹤0.05）. While the generation times in 100-400 μmol/L groups were all shorter than that of the control ［（10.2±3.1） h］ （P﹤0.05）. MLC of metronidazole for T. vaginalis in TYM medium with 200 μmol/L iron ion was （23.44±11.56） μg/ml, significantly lower than that of the control ［（31.25±15.44） μg/ml］ （P﹤0.05）. Conclusion In TYM medium with 100-400 μmol/L iron ion, T. vaginalis trophozoites reproduce faster, and the MLC of metronidazole to the parasites is lower.

Key words: Trichomonas vaginalis, Iron ion, Metronidazole, Minimal lethal concentration