Mechanism of metronidazole resistance after failed eradication of Helicobacter pylori.

Objective To explore the mechanism of metronidazole resistance after failed eradication of Helicobacter pylori(HP).Methods Disk diffusion test was used to select the primary sensitive HP strains(MTZS),primary resistant HP strains(MTZR)and post-failure resistant HP strains.The rdxA gene fragment was amplified by PCR from primary MTZS strains,primary MTZR strains and post-failure MTZR strains.PCR products were sequenced to explore the mechanism of metronidazole resistance.Results Comparison of rdxA genes from primary MTZS strains,primary MTZR strains and post-failure MTZR strains with standard strains showed a high homology in DNA(P0.05).Lower homology in amino acids was shown in primary MTZR was than in primary MTZS and post-failure MTZR(P0.05).Conclusion rdxA gene mutation may be the major factor contributing to primary resistance,although others can be involved in mechanism of metronidazole resistance after failed eradication of HP.