Background: Trichomoniasis is a worldwide protozoan parasitic disease. Considering the importance of the disease in public health and the controversial ideas about the prevalence of drug resistance, this study was designed to determine the prevalence of metronidazole resistance gene in trichomonas vaginalis (T. vaginalis) with PCR-RFLP method in Tehran and in Kashan.

Materials and Methods: In this descriptive study 140 samples of T. vaginalis in patients with T. vaginalis infections were collected and assessed microscopically. Then they were isolated and examined by culturing in dorset's medium, DNA extraction and PCR amplification. The PCR products were analyzed using RFLP and suspected samples were sequenced.

Results: All but 7 samples were T. vaginalis positive by PCR. Sixty-two samples (44.4%) were examined by microscopic, culture and PCR techniques 12 samples (8.5%) by microscope and PCR, 56 samples (40%) by culture and PCR and other 3 samples (2.1%) were positive only by PCR. Two samples (1.5%) were also examined for detection of mutation in 18S rRNA gene with RFLP in Tehran.

Conclusion: This study shows that T. vaginalis infections in the female population living in Tehran are metronidazole-resistant. Since metronidazole is considered as the drug choice for T. vaginalis infections, more studies are recommended for identification of the drug resistance mechanisms and prevention of the disease.