Investigation of frxA gene mutations in metronidazole resistant Helicobacter pylori strains in Tabriz City

Background: Due to the high rate of Helicobacter pylori infection in our country and its treatment failure, and also because of the high prevalence of antibiotic resistance of this bacterium, evaluating causes of Helicobacter pylori resistance to metronidazole and its effect on the therapeutic course is necessary. Materials and methods: A biopsy sample was obtained from 275 suspected patients referred to Imam Reza Hospital in Tabriz. After identification of Helicobacter pylori, bacterial suspension (4 McFarland Standard) was poured onto plates and then antibiotic discs of metronidazole and E-test were placed on it. Metronidazole-resistant strains were detected and mutations in the frxA gene were detected by PCR. Results: Of 112 isolated strains, 85 resistant strains were identified. Resistance to metronidazole was more prevalent in women (50%) than males (35%). Of 85 resistant strains, 70 strains (82.35%) had MIC≥8 in the E-test; while in the DDA, 88 strains were resistant. Of the 20 randomly selected metronidazole-resistant strains, mutation was proved in the frxA gene in 4 strains, but mutagenesis was not proved in susceptible strains. Conclusion: Helicobacter pylori resistance to metronidazole is high in this area and the frequency of this resistance is higher in women than in men. One of the mechanism of resistance of Helicobacter pylori to metronidazole is the occurrence of a mutation in the frxA gene, but this mutation is not the only factor in developing resistance to metronidazole and the evaluation of other molecular mechanisms of resistance to metronidazole seems to be necessary.