Resistance of Helicobacter pylori to antibiotics: the main limitation of current proton-pump inhibitor triple therapy.

Data showing the clinical relevance of Helicobacter pylori resistance, as well as recent data gathered from the MACH2 study, are presented. Despite the problems associated with testing for metronidazole resistance, a correlation between resistance and eradication failure is found in most studies of proton-pump inhibitor triple therapy, in which either amoxycillin or clarithromycin is used as the second antibiotic with metronidazole. Clarithromycin resistance is still low in most communities. Current data are scarce, but indicate that when present it has a higher negative impact on treatment outcome than metronidazole resistance. Resistance frequently emerges with treatment failure, although it is not clear to what extent resistant organisms will spread. In the MACH2 study, culture was used as one of the diagnostic tests and its sensitivity compared with the urea breath test was 99%. In addition, susceptibility tests could be performed on almost all strains. The overall rates of resistance to clarithromycin and metronidazole were found to be 3% (range 1-5%) and 24% (range 16-41%), respectively. There was a 15% decrease in success rate with omeprazole-metronidazole-clarithromycin treatment (from 91 to 76%) for metronidazole-resistant strains. The addition of omeprazole improved the efficacy of metronidazole-clarithromycin dual therapy. The best way to prevent resistance is to obtain the highest possible eradication rate.