[Biological cost of rifampicin resistance in Helicobacter pylori]

The frequence of mutations in the rifampicin resistant (RIF(r)) clones of microorganisms after adaption to ofloxacin and metronidazole was investigated to estimate the biological cost of H. pylori rifampicin (RIF) resistance. Mutations in rpoB gene responsible for RIF resistance of H. pylori were shown to have biological cost and be compensated by additional mutations in the microorganism genome. Comparison of the mutation frequency in the presence of metroniazole demonstrated that the acquired resistance to RIF resulted in changing of the adaptative capacity of the RIF(r) clones of H. pylori to metronidazole. Thus, a significant increase of the mutation frequency (> 700 times) in one of the RIF(r) clones and a broad spectrum of the mutations responsible for resistance to metronidazole vs. the H. pylori initial strain 26695 were observed. The findings could be evident of the fact that the adaptation to RIF changed the properties of the cell on one hand in such a way that its mutation capacity increased and that the target selection on the other hand revealed hypermutable cells, likely usual for the bacterial population.