OMEPRAZOLE MAY EXERT BOTH A BACTERIOSTATIC AND A BACTERIOCIDAL EFFECTON THE GROWTH OF HELICOBACTER-PYLORI (NCTC-11637) IN-VITRO BY INHIBITING BACTERIAL UREASE ACTIVITY

Aims-To assess the potential antibacterial effect of omeprazole, a ben zimidazole proton pump inhibitor, on the growth of Helicobacter pylori in vitro and to evaluate the effect of this compound on bacterial ure ase activity. Methods-The growth of H pylori was observed in Liquid cu lture in the presence and absence of omeprazole (0.8 mg/ml). Urease ac tivity was evaluated in aliquots removed from two hour cultures by mon itoring the initial change in absorbency at 560 nm in the presence of 0.02% phenol red. Results-The minimum inhibitory concentration of omep razole against H pylori was 0.8 mg/ml. The concentration of omeprazole required to inhibit growth was dependent on inoculum density: omepraz ole (0.8 mg/ml) prevented growth from a 1 x 10(6) cfu/ml inoculum, but not from the higher inocula of 10(7) or 10(8) cfu/ml. This is the fir st study to demonstrate that omeprazole exerts a bacteriocidal effect against low bacterial densities and a bacteriostatic effect when bacte rial density is high. When used at the onset of growth, this concentra tion of omeprazole has a bacteriocidal effect after four hours, althou gh it exerts a bacteriostatic effect when added to cultures after the exponential phase. Bacterial urease activity is competitively inhibite d by omeprazole in a dose dependent manner. Conclusion-The results sug gest that omeprazole exerts both a bacteriocidal and a bacteriostatic effect against H pylori and competitively inhibits bacterial extracell ular urease activity.