الفهرس 
Environments in chidhoods that lead toOnly 14 pages are availabe for public view
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Abstract
Two sets of H. pylori isolates are currently differentiated on the basis of their biologic behavior. Type 1 strain produce vaculating cytotoxin (Vac A), an 87 -KDa secreted protein and a 128- KDa surface - located antigen that is the product of cytotoxin- associated gene (Cag A). Type 2 strain has no (Cag A) but sporadically possesses (Vac A) gene without expressing the protein. Type 1 strain H. pylori is more virulent. H.pylori is a spiral-shaped, gram-ve rods measuring O.5X 3.0 Um with 4-6 sheethed flagella. It is microaerophilic organism move in a cork screw manner. It resides in the gastric mucosa as the surface of the human stomach mucosa is the mojor habitate of H.pylori. However, it can be found in remote areas that underwent metaplastic changes in which gastric epithelial cells are present, as esophagus, duodemun or Meckel’s diverticulum. The highest concentration of the bacteria is found in the antral area. H. pylori infection is common world wide between and within population groups, however, prevalence can vary widely. The incidence of H. pylori infection in children may be higher than in adult, thus, many now consider H.pylori is predominatly childhood infection that persist throught life.