Abstract
Helicobacter pylori is a spiral-shaped Gram negative bacteria which was first isolated in pure culture and was considered as a serious threat to gastrointestinal tracts of human. Of particular importance is its role as a risk factor for gastric adenocarcinomas. In the first investigation, we focus on the prevalence of H. pylori virulence factors and its association with clinical outcomes. H. pylori isolates possess unusually high genetic heterogeneity and diversify between geographic regions. Certain H. pylori genotypes are indicated to relate to severe gastrointestinal diseases. Two virulence markers, cagA and babA2, were characterized by PCR in 101 H. pylori isolates from a population who took medical treatment in Veterans General Hospital, Taichung. cagA was detected in 99% of the isolates, while babA2 was present in all of the isolates. The result showed that cagA and babA2 cannot be useful markers for predicting the high-risk patients of H. pylori infection in Taiwan. The current recommended eradication therapies of H. pylori consist of a proton pump inhibitor and several antibiotics. Eradication of H. pylori results in ulcer healing and prevents the recurrence of gastric ulcer and duodenal ulcer. By use of these treatments, some reports suggest the cure rate is more than 90%. However, an eradication failure rate ranging from 20-40% is usually found. In the second part of the study, we investigate whether or not the clinical isolates of H. pylori from patients who failed in therapy were resistant to antibiotics. We also study the altered ability of the H. pylori strains invading into AGS cells by in vitro internalization assay. Bacterial invading activity of the H. pylori isolates from the failure group was significantly higher than those from the cure group (P < 0.01). Our results showed that bacterial epithelial internalization may protect H. pylori from extrcellular bactericidal effects and subsequently induce resistance to intracellular antibiotic. In the third part, we determined and analyzed the role of host cell lipid rafts playing in the invasion of H. pylori into epithelial cells. We identified that internalization of H. pylori was associated with lipid rafts, while adherence was not. We also observed that accumulation of cholesterol at the sites of H. pylori attachment. Furthermore, we demonstrated that VacA, CagA, and BabA2 were able to associate with lipid rafts and have high efficiency for providing the clustering of the rafts. We suggested that this effect would generate platforms for the entry of H. pylori to AGS cells during the infection process.