METRONIDAZOLE RESISTANCE REDUCES EFFICACY OF TRIPLE THERAPY AND LEADSTO SECONDARY CLARITHROMYCIN RESISTANCE

There has been a significant increase in the prevalence of H. pylori r esistance to metronidazole in recent years, while clarithromycin resis tance is still relatively rare. In this study we assessed: (1) the eff ect of primary H. pylori resistance to metronidazole and clarithromyci n on the clinical efficacy of a one-week regimen consisting of omepraz ole, metronidazole, and clarithromycin; and (2) the rate of acquisitio n of secondary antimicrobial resistance after treatment failure. Eight y-seven patients with duodenal ulceration or nonulcer dyspepsia were i ncluded in the study. The primary metronidazole and clarithromycin res istance rates were 35.6% and 3.4%, respectively (all three pretreatmen t clarithromycin resistant strains had concurrent metronidazole resist ance). H. pylori was eradicated in 81.6% of patients. The eradication rate for fully sensitive isolates was 98.2% (55/56) but was significan tly reduced to 57.1% (16/28) for isolates that were resistant to metro nidazole alone and 0% (0/3) in cases of dual resistance (P < 0.001). S econdary resistance to clarithromycin was acquired in 58.3% of cases o f treatment failure. In areas of high prevalence of primary metronidaz ole resistance, this is a significant cause of treatment failure with this triple therapy regimen. This leads to the selection of strains wi th dual resistance that are difficult to eradicate and may contribute to an increase in the prevalence of clarithromycin resistance. In such areas an alternative first-line treatment should be prescribed.