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

Abstract

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 13C urea breath test (UBT) in such children. 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. The overall prevalence of H. pylori infection by 13C-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. 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.