Duodenal Helicobacter pylori infection differs in cagA genotype between asymptomatic subjects and patients with duodenal ulcers

Background & Aims: It is unclear why only a minority of subjects infected b y Helicobacter pylori develop duodenal ulcers (DU). The aim of this study w as to investigate whether the number and type of H. pylori strains in the d uodenum of patients with DU may play a critical role. Methods: Twenty-one p atients with DU and 20 asymptomatic subjects with antral H. pylori infectio n were studied. Paired biopsy specimens were taken from the antrum and from each quadrant of the duodenal bulb. Analyses included extent of duodenal g astric metaplasia, severity of duodenitis, bacterial density, presence of t he cagA gene, and vacuolating cytotoxin activity. Results: H. pylori was cu ltured from duodenal biopsy specimens in 95% of patients with DU and 80% of asymptomatic subjects. Both groups had a similar bacterial density and pro portion of cagA-positive strains in the antrum (86% vs. 75%), but patients with DU had a 20-fold higher density of H. pylori and a higher proportion o f cagA-positive strains in the duodenal bulb (81% vs. 30%). Active duodenit is was present only in patients with DU infected by cagA positive strains i n the duodenum. Conclusions: The results suggest that a high density of cag A-positive strains in the duodenum with severe duodenitis are important det erminants of DU disease.