High prevalence of cagA and vacA seropositivity in asymptomatic Bangladeshi children with Helicobacter pylori infection

Aim: To evaluate the prevalence of antibodies against two major markers of virulence of Helicobacter pylori-cytotoxin-associated gene A (cagA) and the vacuolating cytotoxin gene (vacA) among children in a peri-urban community of Bangladesh, and to evaluate Western blot (WB) assay for detection of H. pylori infection diagnosed by C-13 urea breath test (UBT) in such children. Methods: One hundred and eighty-two children aged 18-60 mo, of the peri-urban community of Dhaka, were screened for H. pylori infection using UBT, and the serum samples were analysed for antibody against cagA and vacA by Western blot. Results: The overall prevalence of H. pylori infection by C-13-urea breath test was 80%. The seroprevalence of cagA with or without vacA, vacA with and without cagA, and both cagA and vacA were 82%, 82% and 81%, respectively. Among children with a positive UBT, 95% were seropositive for both cagA and vacA, indicating that the products of these genes are frequently co-expressed in H. pylori infection in this community. The sensitivity, specificity, positive and negative predictive value of the Western blot test for H. pylori infections, compared to UBT, were 94%, 68%, 92% and 76%, respectively. Conclusion: Compared to UBT, Western blot test is reliable for the detection of H. pylori infection. The high seroprevalence of cagA- and vacA-positive virulent H. pylori strains in an asymptomatic paediatric population indicate that such strains are common in this population and may cause characteristic H. pylori infection in Bangladesh.