Interference on Helicobacter pylori growth and adhesion by omeprazole and other drugs

Helicobacter pylori is the causative agent of gastritis and a co-agent in other gastroduodenal diseases. Gastroduodenal ulcer and MALT-lymphoma in particular, regress when patients are administered antimicrobial agents to eradicate infection. Sometimes eradication is not definitive and is difficult to check. The aim of our study was to test the antimicrobial activity of omeprazole on H. pylori in comparison with ampicillin and other anti-H2 drugs (ranitidine and famotidine), and to evaluate their interference with bacterial adhesion of H. pylori. We also compared results of the agar dilution antibacterial sensitivity test on H. pylori to those obtained using a bacteria adherence to cell monolayers model, to see if drug activity was different against adhered bacteria. We evaluated omeprazole and ampicillin MIC90s (minimum inhibitory concentrations) against 20 H. pylori isolates by traditional agar dilution method and by exposing previously adhered bacteria to an Hep-2 monolayer to different drug concentrations. The activity against bacteria adhered to cell lines was evaluated by counting viable adhered bacteria after 1, 6, 12 hours of contact with drug. Interference with adherence to Hep-2 cells was also tested. Omeprazole and ampicillin MICs were comparable to other findings (omeprazole MIC90 was 12.5 microg/ml and ampicillin MIC90 was 0.016 microg/ml), while higher concentrations were necessary (4 x MIC90) against adhered bacteria. These findings suggest that MICs evaluated with traditional assays can have different predictivity than tests on adhered H. pylori.