Ammonium metabolism and protection from urease mediated destruction in Helicobacter pylori infection.

W D Neithercut, C Williams, M S Hossack, K E McColl

Department of Chemical Pathology, Wirral Hospital NHS Trust.

AIM: To investigate further the intracellular ammonium metabolism of Helicobacter pylori and the mechanism of its urease mediated destruction. METHODS: The mechanism of the in vitro destruction of H pylori was investigated by incubating it in buffer solutions, at pH 6.0, containing isocitrate or alpha ketoglutarate in addition to urea concentrations which had previously been shown to destroy H pylori. RESULTS: The median (range) 5 minute survival of H pylori in 0.2 mol/l citrate buffer (pH 6.0) in the absence of urea was 88% (18-184%) and was similar to its survival in 0.2 mol/l isocitrate buffer in the absence of urea, median 88% (15-274%). In the presence of 50 mmol/l urea the survival of H pylori in the citrate buffer was reduced, 9.9% (0-146%), compared with its survival in isocitrate buffer with the same concentration of urea 37% (0-274%) (p < 0.01). A 72 hour preincubation of the organism with 10 mmol/l alpha ketoglutarate also increased the 5 minute survival of the organism in 0.2 mol/l citrate buffer containing 50 mmol/l urea to 36% (9-145%) compared with its survival in the same buffer but without preincubation with alpha ketoglutarate 0% (0-62%). CONCLUSION: The protection of H pylori from rapid destruction by the supply of compounds used in the intracellular metabolism of the ammonium shows that the urease mediated destruction of H pylori can be explained by intracellular depletion of alpha ketoglutarate as a result of over production of ammonium by uncontrolled urease activity.

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