Genotypic determination of resistance and heteroresistance to clarithromycin in Helicobacter pylori isolates from antrum and corpus of symptomatic patients

The effectiveness of Helicobacter pylori first-line treatment has decreased drastically with the rise of strains resistant to clarithromycin. Therapy failure has also been described in patients with infections by strains with dissimilar antimicrobial susceptibilities. The present study aims to estimate the prevalence of resistance and heteroresistance to clarithromycin in H. pylori isolates from antrum and corpus of Colombian patients. The study material included 126 isolates from antrum and corpus biopsies from 63 symptomatic patients over 18 years old who had a gastric endoscopy performed on them between June 2014 to August 2016. PCR amplification and sequencing of the H. pylori 23S rDNA gene was performed to determine the presence of mutations associated with clarithromycin resistance. Random amplified polymorphic DNA analysis was implemented in cases of resistance and heteroresistance. The overall frequency of resistance to clarithromycin was 38.1% (24/63 patients), of which 19 patients had resistant isolates in both stomach segments (14 with A2143G mutation and 5 with A2142G mutation), and 5 patients had a heteroresistant status. The remaining 61.9% (39/63 patients) presented only susceptible isolates. DNA fingerprinting analysis showed different patterns in 4/22 paired isolates. The high prevalence of H. pylori clarithromycin-resistance obtained (> 15%) constitutes an alert for gastroenterologists and suggests the need for reconsideration of the current eradication regimen for H. pylori in the studied population. The data show that heteroresistance status is an additional factor to be considered in the assessment of resistance. In consequence, it is advisable to examine at least two biopsies from different gastric segments.