Potentiation of the action of metronidazole on Helicobacter pylori by omeprazole and bismuth subcitrate

Treatment failures using triple therapy that include metronidazole, are common in patients infected with metronidazole-resistant Helicobacter pylori in the gastric mucosa. Higher eradication rates in such patients have been described when treatment regimens include bismuth salts compared to regimens that include proton pump inhibitors. In the present study, the synergistic effect of subinhibitory concentrations (0.25-0.5 MIC) of either bismuth subcitrate or omeprazole with metronidazole on the susceptibility of 42 H. pylori strains was investigated by agar dilution method and the Epsilometer test (Etest). With 0.5 MIC of either of the two drugs, the susceptibility of all H. pylori strains to metronidazole was reduced between two to 64 fold and six (27%) metronidazole-resistant strains (with MIC > 4 mg/l) reverted to being metronidazole sensitive. These results suggested that either bismuth salts or proton pump inhibitors may be effective in the treatment of some infections with metronidazole-resistant H. pylori i strains when used in sufficiently high doses. (C) 2000 Elsevier Science B.V. and International Society of Chemotherapy. All rights reserved.