Dissertation
Dissertation > Medicine, health > Basic Medical > Human biochemistry, molecular biology

Helicobacter Pylori cagA、vacA、iceA Status of Zhejiang Province and Relationship to Clinical Outcomes

Author YouJianFei
Tutor FangPingChu
School Zhejiang University
Course Pathogen Biology
Keywords Helicobacter pylori cagA vacA iceA polymerase chain reaction.
CLC R346
Type Master's thesis
Year 2003
Downloads 49
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Background and Aims H. pylori is identified as the chief cause of chronic active gastritis and peptic ulcer diseases (PUD) in human beings and is considered to be a risk factor for the development of gastric adenocarcinoma and MALT lymphoma. So it has been categorized as a group I carcinogen by WHO.By estimated, there are over 50% people infected with H. pylori around the world. But many people remain asymptomatic, only a minority of patients carrying H. pylori develop severe diseases, such as atrophic gastritis, peptic ulcer disease, even gastric adenocarcinoma. The certain pathogenicity mechanism is unknown. One explanation for different clinical outcomes is the diversity of H. pylori strains, otherthan host factors and environmental factors. Now, several genes have been identified that may play a role in the pathogenicity of H. pylori, such as cagA, vacA, and iceA genes. Many epidemiological studies have found that infection with a cagA-positive strains was both highly associated with peptic ulcer disease and with the risk of developing intestinal metaplasia, atrophic gastritis and gastric carcinoma compared to persons harboring cagA-negative strains. vacA, encoding the vacuolating toxin ,is present in all strains, and comprises two variable parts. The s-region (s) exists as sla, sib, sic, and s2 allele, and the m-region (m) occurs as mla, mlb,mlb-m2,and m2 allele. Themosaic combination of s- and m-region allelic types determines the quantity and activity of cytotoxin and thereby is associated with pathogenicity of the bacterium, vac A si/ml strains produce a large amount of toxin, and is associated with peptic ulceration.vacAsl/m2 strains produce moderate amounts, vacAs2/m2 strains produce very little or no toxin. Recently, a novel gene iceA of H. pylori was identified following transcriptional upregulation on contact with gastric epithelial cells. iceA exists as two distinct genotypes, iceA1 and iceA2. And in vivo carriage of H. pylori iceA1 strains has been reported to be associated with peptic ulceration and enhanced acute neutrophilic infiltration, so iceA is suspected to be another virulence factor of H. pylori. The present study aim to investigate Helicobacter pylori cagA, vacAi iceA status of Zhejiang province and relationship to gastric duodenal diseases.Materials and Methods A total of 116 patients with different gastric duodenal diseases, living in Zhejiang province, with culture-proven H. pylori infection were recruited in this study.49 patients were from the Second Affiliated Hospital of Zhejiang University School of Medicine, and the others were from Renming Hospital of Daishan County Zhejiang province. The biopsy specimens from patients were grinded and then spreaded on ECY solid media. After cultured for 5 days at 37 in a microaerobic atmosphere containing 5% oxygen, 10% carbon dioxide, 85% nitrogen, H. pylori strains were identified by the following criteria: characteristic of colony, rapid urease test, oxidase test, morphology on Gram stain. And H. pylori strains were transfer of culture for amplification bacteria. The H. pylori DNA was extracted using the standard method of phenol/chloroform. The primers were according to the references. The cagA, vacA, iceA genotypes were determined by PCR reactions. The reaction conditions were 3 minutes pregeneration at 95 ,followed by 30 cycles of 45 seconds at 94 ,45 seconds at 54 , and 45 seconds at 72 . Final extension was performed for 7 minutes at 72 . The relationship between individual genotypes and the different gastric diseases was assessed with Chi-square ( x 2 ) test, a P value of <0.05 was defined as significant.Results and Discussion Every product of PCR was coincident to thereferences. In all 116 patients, the prevalence of cagA was 100%, vacAsla was 91.4%, vacAm2 was 59.5%, vacAmlb was 12.1%, vacA sla/m2 was 54.3%, vacA sla/mlb was 12.1%, vacAmlb and vacAm2 were both found in 21.6%, there were 6.9% strains carrying neither vacAmlb nor vacAm2 genes. The prevalence of iceAl was

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