THE PROTON PUMP INHIBITOR OMEPRAZOLE INHIBITS ACID SURVIVAL OF HELICOBACTER-PYLORI BY A UREASE-INDEPENDENT MECHANISM (VOL 107, PG 738, 1994)

Background/Aims: Omeprazole, a benzimidazole proton pump inhibitor, ha s an antibacterial effect against Helicobacter pylori at neutral pH an d inhibits its urease activity. The aim of this study was to character ize H. pylori acid resistance and to determine whether omeprazole affe cts its survival at low pH. Methods: We studied survival of H. pylori and other enteric organisms in buffered solutions (pH 2-7) in the pres ence or absence of 10 mmol/L urea and/or omeprazole. Results: In the a bsence of urea, the acid tolerances of wild-type H. pylori, a urease-n egative H. pylori mutant, Escherichia coil, and Proteus mirabilis were similar. In the presence of urea, the survival of the wild-type H. py lori at pH 2 was significantly greater than that of the other organism s. Omeprazole (100 mu g/mL) had a marked inhibitory effect on the surv ival of both wild-type and urease-negative H. pylori at low pH, and si milar effects on E. coli, P. mirabilis, and Salmonella typhimurium. Co nclusions: Whereas survival of H. pylori below pH 4 is urease dependen t, H. pylori uses non-urease-mediated mechanisms at or above pH 4. Ome prazole inhibits the survival of H. pylori at low pH through a mechani sm independent of its effect on urease, an antibacterial effect that e xtends to other enteric bacteria.