Early infant gut flora and neutral oligosaccharides in colostrum in relation to allergy development in children

Sammanfattning: Today, atopic allergy is the most common chronic disease among children in the developed world. The increase in allergy prevalence during the past decades in these countries might be associated with lower microbial exposure. The gut flora, consisting of approximately 800 different species of bacteria, has been postulated to be important for the development of a fully functional immune system. Essentially, these bacteria are in constant contact with the gut flora associated lymphoid tissue, the largest lymphoid tissue of the human body. Following birth, the sterile gut of the newborn is immediately colonised by various bacterial species. Actually, alterations in the infant gut flora have been associated with allergy development.Human milk is the major food in infancy and could thus influence the composition of the infant gut flora. Immunomodulatory components in human milk might differ between mothers and could therefore explain the contradictory results seen regarding breastfeeding and allergy development. Oligosaccharides, the third most abundant solid component in human milk, survive the passage through the stomach and are utilised by the gut microbiota. We analysed nine abundant neutral oligosaccharides in colostrum samples from allergic and non-allergic women and related to subsequent allergy development in their children. We found a considerable variation in the concentration of neutral oligosaccharides in colostrum, which was not to be explained by the allergic status of the women. Neither was the consumption of neutral colostrum oligosaccharides related to the allergy development in children.Relevant bacterial species in early faecal samples were analysed, with Real-time PCR, and related to allergy development in children followed up to five years of age. Infants who harboured Lactobacilli (L.) group I (L. rhamnosus, L. paracasei, L. casei) at 1 week of age and Bifidobacterium adolescentis at 1 month of age developed allergic disease less frequently during their first five years than infants who did not harbour these bacteria at the same time (p=0.004 and p=0.008 respectively).In conclusion, the work presented in this thesis implies the importance of a diverse gut flora early in life for the development of a fully functional immune system. However, consumption of colostrum with high amounts of neutral oligosaccharides does not protect against early allergy development.