Distribution Of Cag PAI In Helicobacter Pylori From Daishan County Where Gastric Carcinoma Has A High Prevalence In Zhejiang Province

Background and Aims Helicobacter pylori (H. pylori) is a Gram-negative spiral-shaped microaerophilic bacterium that colonizes the gastric mucosa of human stomach.. Australian scientists named Warren and Marshall for the first time isolated this bacterium from the human gastric biopsy specimens in 1982. Infection of H. pylori has been implicated as the major cause of gastritis and peptic ulcer, and also appears to be associated with gastric adenocarcinoma, gastric mucosa-associated lymphoid tissue lymphoma and primary gastric non-Hodgkin's lymphoma. In 1994, H. pylori was declared group I carcinogen for gastric cancer by WHO. More than 50% of the world's population is infected with H. pylori and the prevalence of H. pylori infection is 25-50% in Western nations. In the developing countries, the prevalence of H. pylori infection is 60% in children and 80-90% in adults. In most patients (80%) H. pylori does not cause clinical symptoms, but 10-20% of infected patients will develop gastritis and peptic ulcer. A smaller percentage (0.1-4%) of infected patients will develop gastric adenocarcinoma. The certain pathogenicity mechanism is unknown. One explanation for different clinical outcomes is the diversity of H, pylori strains, other than host factors and environmental factors. There is growing evidence that genetic differences among strains help determine the clinical outcome of infection.The cag pathogenicity island (cag PAI) is considered to be one of the major virulence factors of H, pylori. Many epidemic logical studies have found that infection with cag PAI positive strains was highly associated with peptic ulcer, atrophic gastritis and gastric cancer. The cag PAI encode a type IV secretion system, which is used to: (i) translocate the bacterial effector protein CagA into different types of eukaryotic cells; and (ii) induce the synthesis and secretion of chemokines, such as interleukin-8 (IL-8). The genes of cagM, cagT and ORF13 in cag PAI were found to be absolutely essential for translocation of CagA into host cells and for the ability of H , pylori fully to induce transcription of IL-8. The product of ORF10 is absolutely essential for the translocation of CagA, but not for the induction of IL-8. However, the distribution of cag PAI in H. pylori from Daishan County where gastric carcinoma has a high prevalence in Zhejiang Province and their relationship with the gastroduodenal diseases remain unclear. Because of having representative spacing sequences along the cag PAI and playing an important role in pathogenicity of cag PAI, the genes of cagA, cagM, cagT, ORF13 and ORF10 were selected and amplified by polymerase chain reaction (PCR) to evaluate the distribution in H. pylori from Daishan County where gastric carcinoma has a high prevalence in Zhejiang Province, their relationship with the gastroduodenal diseases and the difference of the cag PAI of H, pylori from Daishan County and Hangzhou City.Materials and Methods A total of 124 H. pylori isolates was obtained from H pylori-infected adults who had undergone upper gastrointestinal endoscopy at the Hospital of Daishan County in Zhejiang Province. The patients consisted of 90 men and 34 women with a mean age of 42.7 years (ranging from 16 to 71 years) and classified into 3 groups with chronic gastritis (n=60), peptic ulcer (n=59) and gastric adenocarcinoma (n-5). A total of 47 H. pylori isolates was obtained from H. pylori-infected adults who had undergone upper gastrointestinal endoscopy at the Second Affiliated Hospital of Zhejiang University. The patients consisted of 25 men and 22 women with a mean age of 43.3 years (ranging from 24 to 67 years) and classified into 2 groups with chronic gastritis (n=41), peptic ulcer (n=6). The classification of patients was based on the results of endoscopic and histologicalexamination. Biopsy specimens were cultured on ECY-selective agar plates at 37 for 5 days, under 100% humidity and microaerophilic conditions (5%O2, 10%CO2, and 85% N2). H. pylori was identified by the following criteria: characterist...