Mutations of the Helicobacter pylori genes rdxA and pbp1 cause resistance against metronidazole and amoxicillin.

To investigate amoxicillin and metronidazole resistance of Helicobacter pylori, we compared putative resistance genes between resistant strains obtained in vitro and their sensitive parent strain. All metronidazole-resistant strains had rdxA mutations, and an amoxicillin-resistant strain had pbp1 and pbp2 mutations. By transforming PCR products of these mutated genes into antibiotic-sensitive strains, we showed that rdxA null mutations were sufficient for metronidazole resistance, while pbp1 mutations contributed to amoxicillin resistance of H. pylori.