| Helicobacter pylori(H. pylori) infection causes chronic gastritis (CG), peptic ulceration (PU) and gastritis MALT lymphoma, and is an important risk factor for gastric adenocarcinoma. Most infections are asymptomatic, and only partial infections develop Clinical diseases with obvious symptom. Two major bacterial virulence markers have been described, expression of vacuolating cytotoxin activity encoded by vacA and the presence of cagA (cytotoxin-associated gene A), and the CagA protein is secreted by the bacteria into gastric epithelial cells where it initiates cytoskeletal rearrangements , and enhances gastric epithelial cells to express IL-8.vacA, the gene encoding the vacuolating cytotoxin, is present in nearly all H. pylori strains, and the activity of this cytotoxin is found in about half of H. pylori strains. Analysis of vacA from many strains indicates the existence of two main regions, the signal and middle regions. In general, the signal region exists in one of three subtypes (s1a, s1b or s2), and the middle region possesses one of two subtypes (ml or m2). Other variants of the signal and middle region (s1c,m1 a, m1b, m1b-m2, et al.) have been described in some populations. Production of the vacuolating cyctotoxin is related to the mosaic structure of vacA; for instance, type s1/m1 and s1/m2 strains produce high and moderate levels of toxin, respectively, whereas s2/m2 strains produce little or no toxin.cagA is present in approximately 60-70% of H. pylori strains from Western patients, Various studies have demonstrated that infection of H. pylori strains with cagA+ and /or vacA s1 /m1 are more likely to result in PU.However, in Korea, Japan, et al, about more than 90% H. pylori isolates carry cagA gene, and the distribution of vacA genetype in partial Asia countries is different from west countries.In addition, some studies from other countries have suggested that more than one H. pylori strain with different cagA and vacA status may coexist within the human stomach, and that the multiple-strains coinfections are associated with PU. However, similar studies about coinfection of H. pylori strains is seldom done in our country.Therefore, in this study, the cagA status and vacA genotypes and mixed infections of H. pylori in Zhejiang patients is analyzed, and the frequency of the genotypes with gastric disease is compared, Which is contributed to reveal pathogenic mechanism, traits of transmission, and infectious source of H.pylori in local area.Objective: To analyze the vacA status and cagA genotypes and mixed infections of H. pylori in Zhejiang patients by PCR, and compare the frequency of the genotypes with gastric disease. To determine dominant cagA-vacA genotypes of H.pylori in patients suffing from CG or PU, and to understand the correlation of different genotype H.pylori infection, coinfection and thegastroduodenal diseases.Methods: H. pylori strains were isolated from antrum and corpus samples from 42 patients with CG and 36 patients with PU. PCR was used to detect cagA and the s and m regions of vacA in 156 H. pylori isolates from both the antrum and corpus. Parts of the amplification products were sequenced after T-A cloning. The distribution of H. pylori genotypes and coinfection in CG and PU was analyzed.Results: Almost all of the isolated H. pylori strains were cagA positive. Region of vacA, only one genotype of signal region (s1a) and four genotypes of the middle region (m1, m2, m1b and m1b-m2) were found. The proportion of s1a/m1, s1a/m2, s1a/m1b, s1a/m1b-m2 and coinfection of multiple H. pylori strains in 78 isolates from antrum samples was 6.4%, 55.1%, 26.9%, 1.3% and 3.8%; and the according proportion of those from corpus samples was 6.4%, 53.8%, 25.6%, 3.8% and 5.1% , respectively. Sixteen (20.5%)of the patients had multiple H. pylori strains with different cagA and vacA genotypes, and multiple samples were better than single sample from one stomach to increase the detection positive proportion of coinfection. In comparison with the reported sequences of H...
|
PDF Full Text Request