Bactericidal activity of lansoprazole and omeprazole against Helicobacter pylori in vitro.

The minimum inhibitory concentrations of 39 Helicobacter pylori strains against antibiotics (ampicillin, tetracycline, metronidazole), colloidal bismuth subcitrate and proton pump inhibitors were assessed by the agar dilution method. 20.5% of the strains were metronidazole resistent. The comparison of the bactericidal action of omeprazole and lansoprazole in a killing curve assay showed a dose-dependent reduction of viable bacteria after 24 h, lansoprazole being more effective than omeprazole. Under varying pH conditions, the antibacterial activity of lansoprazole was limited to a pH range of 6-7, reducing bacterial numbers up to 4 logarithmical steps within 24 h.