To carry out phylogenetic analysis for drug-resistance genes from clinical isolates of Helicobacter pylori (Hp) among patients with gastric diseases from Tibet, China.

METHODSHp strains were isolated and cultured from saliva and gastric mucosal tissues derived from patients with gastric diseases. Nine strains (including 5 isolated from oral tissues, 1 isolated from gastric tissues, and 3 representative strains of SS international standard strains used for animal models) were tested for common antibiotic resistance. Together with an ACTT 11637 international standard strain, these were subjected to re-sequencing to obtain drug-resistance genes. Such genes from various sources were compared with the resistance genes of Hp strains recorded by the NCBI website. Combined with results of drug-resistance experiments, correlation between molecular evolution and drug-resistance was analyzed.

RESULTSTesting of gastric mucosal tissues and salivary samples from 217 patients has found 89 Hp strains, which yielded a total infection rate of 41.01%. The resistance rates of 9 representative Hp strains for clarithromycin, amoxicillin, metronidazole, levofloxacin and tetracycline were 77.8%, 77.8%, 44.4%, 77.8%, and 77.8%, respectively. Compared with the reference strain, the similarity between clarithromycin-resistance genes was 99%, and that between amoxicillin- and metronidazole-resistance genes was 96%-97%. A2143G mutation was also found in clarithromycin-resistant genes of three Hp strains.

CONCLUSIONThe sensitivity of Hp to metronidazole is much higher in patients from Tibet region, and the sensitivity of Hp to clarithromycin, amoxicillin, levofloxacin and tetracycline is poor. Resistance mutations are consistent with drug resistance.