The effect of omeprazole dosing on the isolation of Helicobacter pylori from gastric aspirates

Background: Animal experiments suggest that omeprazole dosing increases she dding of Helicobacter into the gastric lumen, and hence into gastric juice. Aim: To assess the effect of omeprazole dosing on the yield of H. pylori fr om gastric aspirates of infected volunteers, Methods: Six serial nasogastric aspirates, three before and three during do sing with omeprazole 40 mg b.d., were obtained for culture from 10 H, pylor i infected volunteers and one uninfected volunteer. To reduce contamination , samples were diluted 1:10 with Maximum Recovery Diluent (MRD: pH 7.0) or HCl-KCl buffer (pH 2.2) prior to culture on Columbia and Dent's agar, Results: Undiluted gastric juice cultures were rapidly overgrown by upper r espiratory tract flora, HCl-KCl dilution resulted in isolation of H, pylori from 77% of infected subject aspirates before, and 67% of aspirates during dosing with omeprazole, The yields were significantly lower with MRD dilut ion, 47% and 10%, respectively, Omeprazole dosing significantly decreased t he yield after MRD dilution, but not after HCl-KCl dilution. Conclusions: Decreasing intragastric acidity, by dosing with omeprazole, de creases the isolation of H. pylori from routinely processed gastric aspirat es. In vitro acidification of gastric aspirates, by HCl-KCl dilution, incre ases the isolation of H. pylori both before and during omeprazole dosing.