The association between genes cagA, vacA and iceA of helicobacter pylori and peptic ulcer diseases

Abstract

Helicobacter pylori infection causes gastric inflammation and gastritis which increase the risk for peptic ulcer disease (PUD) and gastric cancer. It is estimated that more than half of the world's population is infected with H. pylori. The etiologic factors contributing to clinical outcome include environmental factors, genetic factors of host and virulence factors of H. pylori. Several genes of H. pylori play a key role in pathogenesis such as cagA, vacA and iceA genes. The predominant H. pylori strains circulating among geographic locations differ in regard to genomic structure. The prevalence of more pathogenic bacterial genotype in certain areas may have important epidemiological consequences and be associated with the severity of H. pylori-related diseases in such regions. In addition, previous studies demonstrated that the relationship between virulence genes of H. pylori and clinical outcome is still controversial and varies between each ethnic group. Because of this diversity of reports associating the virulence genes with the clinical outcome from different geographic regions, it is important to analyze the association between genes cagA, vacA and iceA of H. pylori and clinical outcome in Thai setting. The aim of this study was to examine the prevalence of genes cagA, vacA and iceA of H. pylori in patients with PUD compared with patients with non-ulcer dyspepsia (NUD) and to determine the association of these genes with PUD. In this study, 40 H. pylori isolates were obtained from PUD patients and 40 isolates from NUD patients. Genes cagA, vacA and iceA of H. pylori were identified by using polymerase chain reaction (PCR) with specific primers. The result of this study demonstrated that cagA positive, vacA si, m2 and iceA2 genotypes were found predominantly in H. pylori in Thailand .The presence of either cagA, allelic variant vacA and iceA alone does not have a predictive value as a risk marker for clinical outcome of H. pylori infection. In addition, high prevalence of mixed iceA isolates (48.75%) was found in Thai patients. All of these isolates contained single vacA genotype which suggests the presence of mixed iceA genotype in one strain. From analysis, vacA sla, mixed iceA genotype was found to be significantly associated with PUD (P=0.04, OR=2.51, 95%CI=1.05-6.04). Therefore, vac A sla, mixed iceA genotype may be regarded as marker for predicting the peptic ulcer disease in Thai setting if the mixed iceA genotype has been proven to be really existed.