[Mechanism of drug resistance in Helicobacter pylori]

Clarithromycin is one of the most important antibiotics for H. pylori eradication. However, 5-10% was reported to be resistant. It has been shown that one point mutation in the 23S rRNA gene is associated with resistance to clarithromycin. To detect H. pylori infection and the mutation simultaneously, we have designed PCR primers specific for H. pylori, and established assays of PCR-RFLP and PCR-preferential homo-duplex formation (PHFA). Using this assay, we can detect mixed infections with wild and mutant-strains. The prevalence of mutant infection increased through clarithromycin-based eradication. However, the existence of mutant strains had been confirmed before therapy in most cases who 'converted' to mutant after therapy. Metronidazole is also one of the most important antibiotics for eradication. However, 5-50% was reported to be resistant. It has been shown that rdx gene mutation is associated with resistance. It is reported that inactivation of the rdx gene is frequently, but not always, associated with resistance to metronidazole. Amoxicillin resistant strains were rare (1.2% in Japanese strains). It is reported that penicillin-binding protein might play a role in the resistance. By detecting of the resistance based on the molecular mechanism, patients can be treated with adequate antibiotics with information about resistance.