Characterization of 23S rRNA gene mutation in primary and secondary clarithromycin-resistant Helicobacter pylori strains from East China.

BACKGROUND/AIMS Clarithromycin is an effective antibiotic for treating Helicobacter pylori; however, the development clarithromycin- resistance by multiple strains prevents the eradication of Helicobacter pylori. We aimed to characterize mutations in the 23S rRNA gene of primary clarithromycin-sensitive, primary clarithromycin-resistant and secondary clarithromycin-resistant Helicobacter pylori strains that were collected in East China and elucidate the mechanisms of clarithromycin resistance. MATERIALS AND METHODS The disk diffusion test and E-test method were used to determine the clarithromycin susceptibility of clinical Helicobacter pylori strains. The 23S rRNA gene fragments were amplified by polymerase chain reaction from 18 primary clarithromycin- resistant strains, 15 primary sensitive strains and 8 secondary clarithromycin-resistant strains. Polymerase chain reaction-products were sequenced to determine mutations of the 23S rRNA gene. RESULTS We found an A2143G (8 strains) mutation in primary clarithromycin-resistant strains, an A2143T (5 strains) mutation in secondary clarithromycin-resistant strains; but no mutations were found in position 2143 of sensitive strains. A T2182C mutation in primary clarithromycin-sensitive, primary clarithromycinresistant and secondary clarithromycin-resistant strains was found with a prevalence of 86.7% (13 strains), 72.2% (13 strains) or 87.5% (7 strains), respectively. In addition, we found a G2254T (8 strains) and a G2172T (7 strains) mutation in secondary clarithromycin- resistant strains. These point mutations were absent in primary clarithromycin-resistant and -sensitive strains. CONCLUSION The gene mutation in position 2143 was associated with resistance to clarithromycin, but the mutation was different between primary and secondary clarithromycin-resistant strains. The T2182C mutation was not associated with clarithromycin resistance. Two new hotspot mutations: G2254T and G2172T, in 23S rRNA were discovered in secondary clarithromycin-resistant strains.