Prevalence of Helicobacter pylori and its CagA subtypes in gastric cancer and duodenal ulcer at an Austrian tertiary referral center over 25 years.

Background And Aims: The prevalence of Helicobacter pylori (H. pylori) tends to be lower in Western countries such as central Europe compared with Asia. The virulence of H. pylori is influenced by its subtype composition, most importantly by the presence or absence of different types of cytotoxin-associated gene A(CagA). This study aimed to assess the prevalence of H. pylori and its respective CagA phenotype in a large retrospective cohort of patients with gastric cancer or duodenal ulcer at a Western tertiary referral institution.

Methods: H. pylori positive gastric biopsy samples from patients diagnosed with the afore mentioned diseases within the past 25 years were re-evaluated by histology for H. pylori and status of gastritis. Confirmed H. pylori positive cases were processed for immunohistochemistry (IHC) for H. pylori,CagA, and EastAsiantype CagA.

Results: The prevalence of H. pylori positive gastric biopsy samples decreased from 20.7% to 2.3% within the study period. Among the gastric cancer patients, the H. pylori positive rate was 16.6%, and didn't show significant changes over time (p = 0.38). Contrary, the H. pylori positive rate of duodenal ulcer decreased significantlyfrom 40% to 5% (p = 0.01). Within H. pylori positive groups ofboth diseases, CagA was highly detected at IHC (86% and 78%, respectively). Except for a few patients originating from East Asian countries, all CagA detected in this study were of Western type.

Conclusion: In this first Western investigation on the chronological prevalence of H. pylori and its most relevant subtypes, Western type of CagA was highly detected in two important index diseases of the pathogen. This raises further questions about the virulence of this subtype.