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

Treatment failures using triple therapy that include metronidazole, are com mon in patients infected with metronidazole-resistant Helicobacter pylori i n the gastric mucosa. Higher eradication rates in such patients have been d escribed 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 su bcitrate or omeprazole with metronidazole on the susceptibility of 42 H. py lori strains was investigated by agar dilution method and the Epsilometer t est (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 bismu th salts or proton pump inhibitors may be effective in the treatment of som e infections with metronidazole-resistant H. pylori i strains when used in sufficiently high doses. (C) 2000 Elsevier Science B.V. and International S ociety of Chemotherapy. All rights reserved.