Eradication: Due to its causal role, eradication of Heiicobacter pylori has become an essential part of therapy for many gastroduodenal diseases. Treatment is based on antibiotics as for any infectious disease. Generally two antibiotics, clarithromycin and amoxicillin or metronidazole and an antisecretory agent are combined in a 7-day regimen. Development of resistance: The main cause of treatment failure is acquired H. pylori resistance to clarithromycin and/or metronidazole. Macrolide resistance results from defective ribosome binding and is associated with a point mutation on the gene encoding for the 23S ribosomal RNA. Strong resistance is acquired. Nitroimidazole resistance appears to result form the incapacity of H. pylori to reduce the nitrate moiety necessary for toxicity. There is a minimum inhibitory concentration gradient. Epidemiological data show that the rate of primary resistance in France is about 10% for clarithromycine and 30% for metronidazole, a rate which would allow use without susceptibility resting for every case. Good compliance is the key to avoiding development of resistance during treatment. In case of treatment failure: Susceptibilty tests are required before attempting a second eradication after initial failure. Though difficult, culture of the H. pylori strain is required to determine the most effective antibacterial agent. In case of nitroimidazole resistance, amoxicillin can be used with clarithromycin and a proton pump inhibitor and metronidazole in case of clarithromycin resistance with amoxicillin and proton pump inhibitor treatment Combination regimens using ranitidine instead of a proton pump inhibitor should be given for 14 days instead of 7. If resistance to both antibiotics is observed, the amoxicillin-metronidazole-proton inhibitor combination for 10 days at a higher dose of metronidazole (500 mg t.i.d.) is recommended. Trials with other compounds are required for such difficult cases. (C) 1997, Masson, Paris.
