Background: Helicobacter pylori infection is generally acquired in childhood and persists as an asymptomatic infection for decades in most infected individuals. Only a minority develops a clinical outcome even in childhood, such as peptic ulcer. It has been reported that H. pylori infection with the type I strain, which expresses the VacA and CagA antigen, is associated with peptic ulcer.
Aim: We examined the diversity of vacA and cagA genes in isolates obtained from Japanese paediatric patients with peptic ulcer or chronic gastritis to investigate the relationship between genetic diversity and clinical outcome.
Methods: The diversity of vacA and cagA genes was investigated by PCR and sequence analysis in 30 isolates obtained from Japanese paediatric patients with peptic ulcer (eight strains) or chronic gastritis (22 strains).
Results: All isolates from Japanese children were cagA-positive strains. Twenty-six strains (86.7%) had East Asian type CagA, and 4 (13.3%) had Western type CagA. The predominant vacA genotype was s1c/m1b (22/30, 73.3%). There was no significant association between the diversity of cagA and vacA genes and clinical outcome. All four children infected with Western CagA strain had a history of overseas travel or residence.
Conclusion: The predominant genotype of H. pylori in Japanese children is East Asian CagA and vacA s1c/m1b genotype, regardless of clinical outcome. Japanese H. pylori strains are homogeneously of the East Asian type; however, Western strains can be introduced into Japan concomitant with host movement from foreign countries in childhood.