Negative Effect of Proton-pump Inhibitors (PPIs) on Helicobacter pylori Growth, Morphology, and Urease Test and Recovery after PPI Removal - An In vitro Study

BackgroundProton-pump inhibitor (PPI) consumption does lead to false-negative results of Helicobacter pylori diagnostic tests such as biopsy culture and rapid urease test (RUT). Materials and MethodsHelicobacter pylori isolates from 112 dyspeptic patients with (56.5%) or without (43.5%) PPI consumption were recruited for examining the negative effects of omeprazole (OMP), lansoprazole (LPZ), and pantoprazole (PAN) on H.pylori viability, morphology, and urease, invitro. The effect of a sublethal concentration of OMP on bacterial features and their recovery after removal of OMP was also assessed. ResultsOf 112 culture-positive gastric biopsies, 87.5% were RUT positive and 12.5% RUT negative. There was a significant correlation between negative RUT results and PPI consumption (p<.05). OMP (minimum inhibitory concentration, MIC 32g/mL) and LPZ (MIC 8g/mL) inhibited the growth of 78.6% of H.pylori isolates. OMP and LPZ inhibited urease of 90.3% of isolates between 0 and 40minutes and 54.4% between 20 and 40minutes, respectively. PAN did not inhibit H.pylori growth and urease. Three 3-day (9days) consecutive subcultures of H.pylori on brucella blood agar (BBA) supplemented with OMP resulted in reduced bacterial viability (1+), compared with control (4+), change of spiral morphology to coccoid, and reduction in pink color intensity in urea agar. Bacterial growth (1+), morphology, and urease test did not improve after the first 3-day and second 3-day (6days) subcultures on BBA. However, relative recovery occurred after the third 3-day (9days) subculture and complete recovery was observed after the fourth 3-day (12days) subculture, as confluent growth (4+), 100% spiral cells, and strong urease test. ConclusionProton-pump Inhibitors exert transient negative effects on H.pylori viability, morphology, and urease test. Accordingly, cessation of PPI consumption at least 12days before endoscopy could help avoiding false-negative results of H.pylori diagnostic tests.