Helicobacter pylori infects over half of adults worldwide. Colonization begins in childhood, and contributes to gastroduodenal disease in adult life. Strains obtained close to colonization are rarely encountered, as they require isolation from young children, yet a detailed study of such strains is critical to understanding H. pylori associated disease. Our study will be conducted in The Gambia, W. Africa, the ancestral home of many African Americans, in a population with a high early childhood incidence of H. pylori colonization. The sadly frequent need for the use of naso-gastric tubes to intensively re-feed malnourished infants, and the high early childhood incidence of H. pylori infection, allow us a unique opportunity to investigate colonizing strains of H. pylori, and further develop appropriate local approaches to disease management. Our goal is to evaluate new methods for culturing H. pylori strains from young children, and to compare these to those obtained from adults. We propose that the transition from childhood colonization to adult disease state is affected by multiple factors including evolution of genotypes of colonizing H. pylori strains themselves, so that H. pylori strains from Gambian children will differ genetically from strains from chronically colonized adults. We have two specific aims: Aim 1: To compare the range of genotypes obtained from H. pylori cultured from gastric biopsies from Gambians, with those obtained by culture of gastric juice aspirate, from the same subjects: Aim 2: To assess the relatedness of child strains and those from close adult relatives, cultured from naso-gastric aspirates. The data from these experiments will give us our first insight into the changes that may occur in the H. pylori genome during the period of colonization of its unique niche, the human stomach. We anticipate that our work will allow further understanding of why the clinical diseases associated with chronic H. pylori colonization in West Africa differ from those seen in industrialized nations, and enable the development of appropriate treatment strategies for communities such as The Gambia.