The proton pump inhibitor omeprazole inhibits acid survival of Helicobacter pylori by a urease-independent mechanism.
OBJECTIVE
Omeprazole, a benzimidazole proton pump inhibitor, has an antibacterial effect against Helicobacter pylori at neutral pH and inhibits its urease activity. The aim of this study was to characterize H. pylori acid resistance and to determine whether omeprazole effects its survival at low pH.


METHODS
We studied survival of H. pylori and other enteric organisms in buffered solutions (pH 2-7) in the presence or absence of 10 mmol/L urea and/or omeprazole.


RESULTS
In the absence of urea, the acid tolerances of wild-type H. pylori, a urease-negative H. pylori mutant, Escherichia coli, and Proteus mirabilis were similar. In the presence of urea, the survival of the wild-type H. pylori at pH 2 was significantly greater than that of the other organisms. Omeprazole (100 micrograms/mL) had a marked inhibitory effect on the survival of both wild-type and urease-negative H. pylori at low pH, and similar effects on E. coli, P. mirabilis, and Salmonella typhimurium.


CONCLUSIONS
Whereas survival of H. pylori below pH 4 is urease dependent, H. pylori uses non-urease-mediated mechanisms at or above pH 4. Omeprazole inhibits the survival of H. pylori at low pH through a mechanism independent of its effect on urease, an antibacterial effect that extends to other enteric bacteria.
McGowan
C C
CC
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
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Blaser
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D002951:Citrates / Q000494:pharmacology*; D019343:Citric Acid; D016480:Helicobacter pylori / Q000187:drug effects* / Q000201:enzymology; D006851:Hydrochloric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D009853:Omeprazole / Q000494:pharmacology*; D054328:Proton Pump Inhibitors; D014510:Urease / Q000502:physiology*
D002951:Citrates; D054328:Proton Pump Inhibitors; D019343:Citric Acid; D014510:Urease; D009853:Omeprazole; D006851:Hydrochloric Acid