Background & aim: Trichomoniasis is the most common non-viral sexually transmitted disease worldwide. In previous studies in women referred to the Yasuj gynecologic clinic, Trichomonas vaginalis infection was reported by three methods: clinical diagnosis (19/04% - 28%), microscopic (42/9% - 41%) and polymerase chain reaction (11%). Parasite resistance to metronidazole is a therapeutic problem. In this resistance, mutation in the parasite ferredoxin gene plays an important role. In the present study, frequency of mutation and determination point of the mutation in this gene, in isolated parasites from patients referring to Yasuj women's clinic in 2017 were investigated.

Methods: In the present descriptive study, forty-six patients with clinical signs of vaginitis were selected. Then, they were asked to fill out a questionnaire. Two swabs of each vaginal sample were taken from each patient. One specimen in a test tube containing physiological serum for microscopic examination and another sample was placed in Dorset medium for growth of the parasite. DNA extraction were extracted using a kit and PCR experiments were performed to confirm the presence of trichomonas vaginalis and fiducoxin genes two times. The sequences of fibridoxin gene pseudo-bands were sequenced by South Korean bioresorpants and blast in the NCBI database to find the location of the mutation. The results were analyzed using descriptive statistics and statistical methods.

Results: Out of forty-six samples, twenty samples (43.44%) were positive for Trichomonas vaginalis in microscopic and culture media and twelve samples (20.08%) were positive in PCR. The ferredoxin gene was reproduced and sequenced in these 12 samples. No mutation in ferredoxin gene was detected in any of the studied samples.

Conclusion: Changes in the ferredoxin gene resulted in metronidazole discontinuation in the treatment of trichomoniasis, which was not seen in the present study samples. It meant that there was no therapeutic resistance associated with ferredoxin gene in these specimens.