In-vitro susceptibility of Helicobacter pylori to ampicillin, clarithromycin, metronidazole and omeprazole.

The in-vitro activities of omeprazole and three antimicrobial agents against 89 clinical isolates of Helicobacter pylori from a population with duodenal ulcer disease were determined by an agar dilution method. Resistance rates were 20% for metronidazole (MIC > 8 mg/L), 1% for clarithromycin (MIC > 2 mg/L) and zero for ampicillin (MIC > 8 mg/L). Omeprazole was relatively active against H. pylori in vitro (MIC < or = 8 mg/L).