**2. Conclusions**

The prevalence of *H. pylori* infection remains high worldwide despite a progressive decline over time, attributed to improved overall living conditions and hygiene. Although often asymptomatic, most infected patients suffer from persistent non-ulcer dyspepsia that, usually later in adulthood, may further progress to more severe conditions. The most common severe complication *H. pylori* is duodenal ulcer, affecting 10 to 15% of the infected adults. Although less frequent, 2 to 5% of the infected adults with non-ulcer dyspepsia progress to gastric ulceration and some ultimately to gastric cancer. These two forms of peptic ulcer-related (organic) dyspepsia differ in prevalence and physiopathology; those suffering with duodenal ulcer are at low risk of developing a gastric ulcer/gastric cancer. The onset of peptic ulcers in childhood is a rare event that may occur shortly after infection, suggesting more virulent *H.* *pylori* strains and more susceptible young patients. *H. pylori*-associated paediatric peptic ulcer disease is, therefore, a privileged natural study model to search for ulcerogenic-specific bacterial biomarkers and implicated molecular mechanisms, a required step to better address this important public health problem. This includes enhanced virulence of the paediatric ulcerogenic *H. pylori* strains that also may have a natural ability to better adapt to the hostility of their niche.
