Prevalence of dual clarithromycin and metronidazole resistance in Helicobacter pylori estimated by molecular methods in Santiago, Chile

BackgroundCurrent available treatments for Helicobacter pylori eradication are chosen according to local clarithromycin and metronidazole resistance prevalence. The aim of this study was to estimate, by means of molecular methods, both clarithromycin and metronidazole resistance in gastric mucosa from patients infected with H.pylori.\n\nMethodsA total of 191 DNA samples were analyzed. DNA was purified from gastric mucosa obtained from patients who underwent an upper gastrointestinal endoscopy at an university hospital from Santiago, Chile, between 2011 and 2014. H.pylori was detected by real-time PCR. A 5exonuclease assay was developed to detect A2142G and A2143G mutations among Hpylori-positive samples. rdxA gene was sequenced in samples harboring A2142G and A2143G mutations in order to detect mutations that potentially confer dual clarithromycin and metronidazole resistance.\n\nResultsNinety-three (93) out of 191 DNA samples obtained from gastric mucosa were H. pylori-positive (48.7%). Clarithromycin-resistance was detected in 29 samples (31.2% [95%CI 22.0%-41.6%]). The sequencing of rdxA gene revealed that two samples harbored truncating mutations in rdxA, one sample had an in-frame deletion, and 11 had amino acid changes that likely cause metronidazole resistance.\n\nConclusionsWe estimated a prevalence of clarithomycin-resistance of 31.8% in Santiago, Chile. The proportion of dual clarithromycin and metronidazole resistance could be, at least, 15.0%. Our results require further confirmation. Nevertheless, they are significant as an initial approximation in re-evaluating the guidelines for H.pylori eradication currently used in Chile.