Helicobacter pylori Virulence Genes Detected by String PCR in Children from an Urban Community in Northeastern Brazil

Abstract

The accuracy of a nested PCR in gastric DNA obtained by a string test for the diagnosis of Helicobacter pylori infection in asymptomatic children was 94.0%. The cagA-positive toxigenic vacAs1m1 strains were the most prevalent strains, indicating that this population is colonized early by the strains associated with gastric cancer. Helicobacter pylori infection significantly increases the risk of development of peptic ulcer disease, distal gastric carcinoma, and gastric lymphoma (1). Infection of the general population with virulent strains, especially those carrying the cagA gene and vacAs1 genotype, is a predictor of increased risk for development of severe H. pylori-associated diseases. However, the majority of the methods used for genotyping H. pylori strains require an invasive procedure, endoscopy, for tissue sample collection and are not indicated in epidemiological studies evaluating asymptomatic individuals, especially children. The string test, a minimally invasive nonendoscopic procedure, seems to be an accurate method to obtain gastric specimens in order to investigate H. pylori virulence genes. It has been demonstrated that the genotypes of H. pylori strains in DNA from the gastric juice or tissue samples are identical (2).Previously we have shown a high prevalence of infection by H. pylori strains carrying the cagA gene and the vacAs1 allele in dyspeptic adult patients who underwent endoscopy in northeastern Brazil (3). Furthermore, we have demonstrated that in this population, the infection is acquired earlier in childhood (4), another predictor of gastric cancer. However, we are unaware of studies evaluating the profile of the circulating strains in children of the general population living in areas at increased risk of gastric cancer. Therefore, our aim was to investigate whether the most virulent strains of H. pylori circulate in asymptomatic children from the population, by obtaining H. pylori DNA in gastric juice or mucus by the string test. We also aimed to evaluate the accuracy of an H. pylori-specific nested PCR for the diagnosis of the infection in asymptomatic children.The study was approved by the Ethics and Research Committee of the Federal University of Ceará. All children and their parents signed the informed consent. Individuals who had participated in previous H. pylori epidemiological studies in Parque Universitário, a low-income urban community in Fortaleza, Brazil, were invited to participate (5). Children who had taken antibiotics potentially active against H. pylori were not included. Fifty children (24 females and 26 males) 8 to 18 years old with a mean age of 14.3 years were evaluated. After a 6-h fast, the children were submitted to the [ 13 C]urea breath test ( 13 C-UBT) (6) and immediately after to the string test. We used a homemade string test with a small capsule, which increased the adherence of the participants, following the protocol previously described, with minor modifications (7). A gelatin capsule containing a 90-cm-long absorbent cotton string was swallowed wit...

CagA phosphorylation EPIYA-C motifs and the vacA i genotype in Helicobacter pylori strains of asymptomatic children from a high-risk gastric cancer area in northeastern Brazil

“…The DNA was extracted directly from the gastric mucus/juice [obtained by the string procedure ( Gonçalves et al 2013 )] using the QIAmp kit (QIAGEN, Germany) according to manufacturer’s recommendations with minor modifications. The DNA concentration was determined by spectrophotometry using NanoDrop 2000 (Thermo Scientific, USA) and the samples were stored at -20ºC until use.…”

“…Furthermore, with respect to the vac A i region, we are aware of only one study evaluating 11 symptomatic Bulgarian children ( Yordanov et al 2012 ). Previously, we have shown a high prevalence of infection by H. pylori strains carrying the cag A gene and the vac A s1 allele in asymptomatic children from northeastern Brazil, a high-risk area for gastric cancer, by evaluating gastric juice/mucus DNA obtained by a string test ( Gonçalves et al 2013 ). In this study, we aimed to characterise the number of CagA EPIYA motifs and the vac A i genotypes in H. pylori DNA from these children.…”

Persistent and TransientHelicobacter pyloriInfections in Early Childhood

“…Whether this is the case in asymptomatic children and/or whether it plays a role in persistence is unknown. Strains containing virulence-associated genes, cagA and the more virulent version of vacA (s1m1), have been documented in isolated samples of asymptomatic Brazilian and Colombian children, but it is unclear if these strains are associated with persistence [14,15].…”

Helicobacter pylori in Pediatrics

“…Ou et al [37] found that the fluorescent quantitative PCR test was more sensitive than conventional methods alone or in combination (p<0.01). A nested PCR had a sensitivity of 93.0% and a specificity of 100% compared with the 13 C-urea breath test (UBT) on gastric DNA obtained by a string test in asymptomatic children [2]. Baskovich et al [38] also detected a surprisingly high number of new cases with H. pylori by PCR, in both the normal biopsies and test cases, suggesting that PCR could detect colonization in asymptomatic patients.…”

“… found that the fluorescent quantitative PCR test was more sensitive than conventional methods alone or in combination (p<0.01). A nested PCR had a sensitivity of 93.0% and a specificity of 100% compared with the 13 C‐urea breath test (UBT) on gastric DNA obtained by a string test in asymptomatic children . Baskovich et al.…”