Prevalence of helicobacter pylori cytotoxic-associated genes and its association with treatment outcomes amongst dyspeptic patients in South Western Uganda

Abstract

Helicobacter pylori (H. pylori) is a gram-negative fastidious bacteria that infect the stomach. H. pylori virulent strains is associated with severe gastritis, ulcerative disease and the upper gastrointestinal malignancies. It’s believed that approximately 50% of the world’s adult population have been colonized by this pathogen and a much higher (80%) in many developing countries. In Uganda, little is known about the prevalence of the major H. pylori virulence genes, the association of H. pylori infections with treatment outcome despite high H. pylori prevalence particularly amongst gastric cancer patients. The aim of this study was to determine the prevalence of H. pylori amongst patients with dyspepsia in Mbarara Hospital, establish the association between infection by H. pylori virulent strains and treatment out-come and to assess the pylogenetic relationship of H. pylori strains obtained from this study with others previously sequenced and deposited in GenBank. The study was conducted as a cohort and constituted 150 dyspeptic patients 18 years and above. Detection of H. pylori stool antigen was done using SD Bioline kit to determine the prevalence of H. pylori. H. pylori 16SrRNA , CagA and VacAs1 genes were amplified and analysed by 2% gel electrophoresis and 16SrRNA and CagA genes were sequenced to asses phylogenetic relationship. Stool repeat test were performed to assess treatment outcome of initially stool positive patients. Differences between presence of H. pylori virulent genes and treatment outcomes were tested using Chi-square tests and association between treatment outcome and virulent genes were explored using modified poisson regression with robust standard errors. The overall prevalence of H. pylori amongst dyspeptic was 58 (40.3%). The prevalence of virulent genes among H. pylori positive patients was 67% (45) for CagA and 76% (52) for VacAs1. Of the fifty five (55) patients re-screened after a month of treatment completion, 47 (85.4%) patients turned negative for H. pylori stool antigen after treatment while 8 (14.6%) remained positive. VacAs1 and CagA genotypes were associated with non-recovery with (aPR = 0.76, 95% CI: 0.623 – 0.931, P = 0.008) and (aPR = 0.80, 95%CI: 0.658 – 0.972, P = 0.025) respectively. H.pylori prevalence amongst dyspeptic patients was low. A higher proportion of those infected with H.pylori have virulent strains of H.pylori and are less likely to respond to treatment. Further studies should be done to establish whether there is a correlation between the presence of H.pylori virulence genes and resistance to the common drugs used in the treatment of H.pylori .