Characterisation of point mutations in domain V of the 23S rRNA gene of clinical Helicobacter pylori strains and clarithromycin-resistant phenotype in central Vietnam

Objectives: The prevalence of clarithromycin (CLR)-resistant Helicobacter pylori is increasing worldwide, including in Vietnam. The aims of this study were to determine point mutations in the 23S rRNA domain V of clinical H. pylori strains in central Vietnam, to estimate the prevalence of phenotypic CLR resistance and to assess the association between 23S rRNA domain V genotype and CLR-resistant phenotype. Methods: Sequencing of the 23S rRNA domain V of H. pylori strains from gastric biopsy specimens was performed for 185 patients with H. pylori-positive chronic gastritis, of which 104 samples were subjected to susceptibility testing to determine CLR resistance. Results: A total of 24 types of point mutation were detected. A2143G and A2142G mutations were observed in 40.5% and 4.3%, respectively. New point mutations were detected (C2041T, C2083T, C2191T, G2220A, G2225A, G2240A, C2273T, T2276C, G2287A, C2399T, A2445G and C2622T). 23S rRNA domain V genotypes were diversified, with combinations of two or more point mutations as well as single point mutations. The rate of phenotypic CLR resistance was 53.8%, increasing from 40.4% in 2012-2014 to 70.2% in 2015-2017 (P= 0.0045). A2143G and A2142G accounted for 89.3% of phenotypically CLR-resistant H. pylori isolates. Conclusions: A diversity of point mutations in the 23S rRNA domain V was observed in clinical H. pylori isolates. The rate of phenotypically CLR-resistant H. pylori is significantly increasing in central Vietnam. Further research is necessary to clarify the role of the combination of 23S rRNA domain V mutations in the molecular mechanism of CLR resistance. (C) 2018 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.