| Abstract: | OBJECTIVE : To investigate the prevalences of metronidazole‐ and clarithromycin‐resistant Helicobacter pylori over the period from 1995 to 1999 in Shanghai, and the molecular mechanism of resistance to clarithromycin. METHODS : A total of 150 H. pylori strains were randomly selected from the isolates collected in 1995, 1997 and 1999, and tested for sensitivity against metronidazole and clarithromycin by using the E‐test. The mechanism of resistance was studied by polymerase chain reaction (PCR)–restriction fragment length polymorphism (RFLP). RESULTS : It was found that 42% (21/50), 57% (27/50) and 70% (35/50) of the tested strains were resistant to metronidazole among the isolates collected in 1995, 1997 and 1999, respectively. In 1995, there was no strain (0/50) resistant to clarithromycin, of which the prevalence rose to 2% (1/50) in 1997, and to 10% (5/50) in 1999. The prevalences of metronidazole‐ and clarithromycin‐resistant H. pylori in 1999 were significantly higher than those in 1995 (P < 0.05). Of nine clarithromycin‐resistant H. pylori strains, eight were found to have an A→G mutation at position 2144 of domain V of the 23S rRNA. CONCLUSIONS : These results suggest a significant increase in the prevalences of metronidazole‐ and clarithromycin‐resistant H. pylori in Shanghai during the 1995–1999 period. The majority (88.8%) of clarithromycin‐resistant H. pylori isolates have an A2144G mutation in domain V of the 23S rRNA. |
