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引起人类胃粘膜感染的革兰氏阴性螺旋状细菌——幽门螺杆菌与胃炎、胃溃疡和胃癌的发病有关。所有幽门螺杆菌都具有强有力的尿素酶、鞭毛和各种粘附素,这些物质对细菌生存于胃环境中和在特异组织中的定居是重要的。有些菌株具有表面暴露的免疫显性抗原,它编码于CagA。另外一些毒株还具有一种细胞毒素,编码于VacA,它可在试管内导致许多上皮细胞系形成空泡。因此幽门螺杆菌至少可再分成两组,带有CagA和(或)细胞毒素的为Ⅰ型,两者均不带的为Ⅱ型。Ⅰ型中有些仅具有CagA而无细胞毒素
Helicobacter pylori, a gram-negative helical bacterium that causes gastric mucosal infections in humans, is associated with the onset of gastritis, gastric ulcers and gastric cancer. All Helicobacter pylori have potent urease, flagella and various adhesins that are important for the bacteria to survive in the stomach environment and to colonize specific tissues. Some strains have surface exposed immunodominant antigens that encode CagA. Other strains also have a cytotoxin, encoded in VacA, which causes many epithelial cell lines to form vacuoles in vitro. Therefore, H. pylori can be subdivided into at least two subgroups, type I with CagA and / or cytotoxin, and type II with neither. Some of Type I only have CagA and no cytotoxins