Nitroimidazole resistance in Helicobacter pylori

The efficacy of a nitroimidazole-containing regimen for the treatment of He licobacter pylori infection is decreased by nitroimidazole resistance. Nitr oimidazoles are metabolized by H. pylori by several nitro-reductases of whi ch an oxygen-insensitive NADPH nitroreductase encoded by the rdxA gene is t he most important. Null mutations in this gene are associated with resistan ce. Susceptibility testing to nitroimidazoles may give variable results. This i s not only related to the slow growth under specific conditions, but also t o variability in the activity of the other nitroreductases and the ability to deactivate toxic metabolites of an NI and to repair DNA damage. Moreover , co-infections with resistant and susceptible bacteria are frequently foun d. The presence of nitroimidazole resistance is related to the previous use of this drug. The prevalence of resistance is rising and nowadays 10-50% o f the isolates are resistant. Resistance reduces the efficacy of a treatment regimen to a variable degree . This is related to efficacy of the other components of the regimen and th e treatment duration. Whether a nitroimidazole is still effective in resist ant strains remains unresolved. When nitroimidazole resistance is present, a nitro-imidazole-containing reg imen should be avoided or a regimen with other highly effective components should be used.