Helicobacter pylori strain types and risk of gastric cancer: a case-control study.

The aim of this novel endoscopy clinic-based case-control study was to explore the influence of different Helicobacter pylori strain types on the risk of gastric adenocarcinoma using isolated bacterial strains, tissue samples, and sera. We included 72 cases with gastric adenocarcinoma and 324 age- and sex-matched controls. Histological characterization, culture, molecular typing of H. pylori genes by PCR (cagA/vacA), conventional IgG ELISA, and immunoblotting (Western blot) for the CagA and VacA proteins were performed. With four tests combined, H. pylori infection was detected in 57 (79%) cases and 213 (66%) controls. A positive association between H. pylori infection and gastric cancer risk was found [odds ratio (OR), 2.1; 95% confidence interval, 1.1-3.9]. Type I (OR, 1.8), intermediate (OR, 2.0), and type H (OR, 0.2) strains of H. pylori presented different serum antibody levels and different levels of association with gastric cancer. Our case-control study, based on molecular characterization and serology, provides further evidence that infection by more virulent strains of H. pylori and the presence of antibodies toward the CagA protein can be used as markers for an increased risk of gastric adenocarcinoma and that the strain types of H. pylori could be used in the future to determine disease outcome.