Helicobacter in The Gambia (Part 1)

Overview

H. pylori infection causes the stomach to become inflamed. The problem usually begins in childhood and leads to stomach problems in adult life. Study participants will be residents of The Gambia, West Africa, and will be studied at the Medical Research Council of Great Britain facility in Fajara, The Gambia. Up to 75 adults 18 years and older and 20 malnourished children 6 months to 2 years of age, who are undergoing endoscopy as part of their medical care, will be studied. (Endoscopy is when a thin, lighted device is used to look inside the body.) During this study procedure, tiny pieces of tissue, called biopsies, will be taken from the stomach and checked for H. pylori infection. Participants found to be infected will be given antibiotic treatment. Participation in the study will last approximately 72 hours.

The overall goal in this pilot project is to implement and evaluate a new method for isolating Helicobacter pylori (H. pylori) strains from young children, and to compare these isolates with those obtained from adults from the same population. This is part I of the study, and part II is described in the Division of Microbiology and Infectious Diseases protocol 06-0004. The transition from childhood colonization to adult disease state may be affected by multiple factors including evolution of genotypes of colonizing H. pylori strains themselves, driven in part by the host response to infection. The hypothesis is that H. pylori strains from Gambian children will differ genetically from the strains of chronically colonized adults from the same community. Genetic and phenotypic characterization of pediatric and adult H. pylori isolates will test for fundamental differences between strains circulating in these 2 age groups, and thereby help evaluate the importance of strain selection and/or genome evolution in such high risk societies. Specific objectives are: to compare the range of genotypes obtained from H. pylori cultured from gastric biopsies from Gambian adults and children undergoing diagnostic upper endoscopy, with those obtained by culture of gastric juice aspirates from the same subjects. This will allow interpretation of results obtained from culture of nasogastric aspirates from children who do not require diagnostic endoscopy, when compared to gastric biopsy-derived H. pylori isolates. Most genotyping will entail polymerase chain reaction tests for virulence markers, limited (focused) DNA sequencing, and tests for susceptibility to metronidazole and frequency of forward mutation. The study population will consist of residents of The Gambia, West Africa. Up to seventy five adults of both sexes and all ages, who are undergoing diagnostic endoscopy as part of their clinical management, and 20 malnourished children of both sexes and less than 2 years of age, who are undergoing diagnostic endoscopy as part of their clinical management, will be studied. All subjects will be studied at the Medical Research Council of Great Britain research laboratories and clinical facility in Fajara, The Gambia. The main outcome measure will be the degree of relatedness between 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 (a computer program for putting DNA sequences together for analysis) and multiple locus sequence typing (MLST) database. There are no outcome measures for human subjects. All laboratory investigations will be conducted upon bacterial isolates.