Helicobacter in The Gambia (Part 2)

This preliminary descriptive study is aimed at providing the first data that will evaluate differences and similarities in genotype between isolates of H. pylori obtained from children and adults living in The Gambia, West Africa, and to assess the likely magnitude of these differences. This protocol describes the application of minimally invasive techniques for H. pylori isolation (developed in the first part of this project and described in a separate protocol, DMID protocol 06-0053) in a population study. Study subjects will be residents of The Gambia, West Africa. Ninety children, aged less than 2 years, requiring therapeutic nasogastric intubation and 30 healthy mothers of these children will be studied. Subjects will be studied at the Medical Research Council (MRC) of Great Britain Research Laboratories and Clinical Facility in Fajara, The Gambia, West Africa. Investigators 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, driven in part by the host response to infection. Researchers hypothesize that H. pylori strains from Gambian children will differ genetically from the strains of chronically colonized adults from the same community. The investigators' genetic and phenotypic characterization of pediatric and adult isolates will test for fundamental differences between strains circulating in these 2 age groups, which may help to evaluate the importance of strain selection and/or genome evolution in such high risk societies. The specific aim of this study is to assess the relatedness of child strains and those from close adult relatives. Study procedures will include aspirating gastric juice through a nasogastric tube used for infant feeding purposes in children who are undergoing intensive in-patient re-nutrition, and culturing H. pylori from these aspirates, and also from parents who accept the invitation to donate a sample of gastric juice for culture through a nasogastric tube inserted temporarily for this purpose. Most genotyping will entail arbitrarily primed polymerase chain reaction DNA fingerprinting, limited (focused) DNA sequencing, especially in cases of isolates with closely related but non-identical fingerprints, and metronidazole susceptibility tests. Genetic and phenotypic characterization of pediatric and adult isolates will test for fundamental differences between strains circulating in these two age groups, and thereby help evaluate the importance of strain selection and/or genome evolution in such high risk societies. Subjects will be studied only once during this 2-year project. If H. pylori are isolated from gastric aspirates, the mother of that child will be asked if they would agree to have a nasogastric tube passed on one occasion to obtain an aspirate of gastric juice for H. pylori culture. The isolates obtained will be subject to DNA analysis and genotyping. Specific points to be addressed by these comparative studies will include direct comparison of strains isolated from children and adults from within the same family or village. This will be the first study to be performed in a society with a high early incidence of naturally acquired H. pylori colonization, and will allow direct comparison between isolates from children and adults from within the same families or village environment, which will provide information about intra-familial and intra-community transmission of infection. The main outcome measure is the degree of relatedness between the bacterial isolates. This will be assessed by visual comparison between random amplification of polymorphic DNA (RAPD) results, by comparison of genotype for alleles of interest, and definitively by sequencing of housekeeping genes to construct phylogenetic trees of relatedness using the STAR program and multiple locus sequence typing (MLST) database. There are no outcome measures for human subjects.