The mutation of the rdxA gene in metronidazole-resistant Helicobacter pylori clinical isolates

Antibiotic resistance is an increasing problem throughout the developed world, and knowledge about different resistance mechanisms is consequential for efficient treatment of bacterial infections. Although metronidazole has been frequently used in treatment regimens for H. pylori infection, but antibiotic resistance is now a major contributing factor in treatment failure. Nevertheless metronidazole has been greatly used as a critical component of combination therapies for H. pylori infection.

This study is trying to describe the mutational mechanisms of metronidazole resistance in H. pylori in our clinical isolates in Isfahanian patients, Iran and compare with the findings of previous studies in world.

MIC values of metronidazole for H. pylori strains were determined by E- test. Both rdxA and glmM genes used for confirmation of isolates as H. pylori and then amplification of another rdxA oligonucleotide pair was done. Finally, the six resistant strains were sent to sequencing for other processing and further analysis was done by software.

The result of six clinical isolates in comparison with 26695, J99 and 69A as a sensitive and resistant reference strains showed plenty of mutations. No frame shift and nonsense mutation was seen in our clinical isolates.

An interesting finding in metronidazole-resistant strains in our study was the detection of one mutation not previously described in the literature in the rdxA gene and this W(209)R substitution presumably plays a role in inducing metronidazole resistance.