Mining milk for factors which modulate host-microbial interactions in vitro

Human milk oligosaccharides (HMO) have been reported to increase the adhesion of Bifidobacterium longum subsp. infantis ATCC 15697 (B. infantis ATCC 15697) to human colonic adenocarcinoma, HT-29 cells. In this thesis, various commercial ingredients were selected as alternatives to HMO, including lactose (Chapter VI), and fractions isolated from bovine, caprine (listed in Table 1, Chapter II), and camel milk (Chapter V). B. infantis ATCC 15697 was chosen for screening assays based on previous in vitro adhesion studies and its evolutionary adaptation to the consumption of milk glycans. As adhesion assays are slow-through-put, miniaturised high-throughput assay requiring substantially lower sample quantities were developed for screening purposes. Miniaturised and conventional adhesion assays were shown to be comparable. Increased B. infantis ATCC 15697 adhesion was observed in the presence of an immunoglobulin enriched powder (IGEP) and Goat Milk Oligosaccharides (GMO). These components were then studied in detail in Chapter III and Chapter IV respectively. In Chapter V, a camel milk fraction (CMF) was shown to increase the adhesion of three of the seven Bifidobacterium strains. In Chapter VI, lactose was found to increase the adhesion B. breve UCC2003 to HT-29 cells. Campylobacter jejuni, a common bacterial cause of human gastroenteritis, was used to investigate if increased bifidobacterial adhesion to HT-29 cells could provide protection against pathogenic colonisation. GMO, IGEP, CMF and Lactose treated some Bifidobacterium strains decreased the adherence of C. jejuni to HT-29 cells by varying amounts as discussed in detail in Chapters, III, IV, V and VI. Overall, these studies build a strong case for the use of milk components from a variety of domestic animal milks to modulate of intestinal bifidobacteria, with oligosaccharides showing multiple bio-functionalities, while lactose, CMF and IGEP offer more potential in terms of commercial viability. Future research should aim to elucidate the intricacies of how these milk components interact with bifidobacteria, thereby identifying novel therapeutic targets and a means by which to maintain or restore host gut health.

Funder

Teagasc

Publisher

NUI Galway

Rights

Attribution-NonCommercial-NoDerivs 3.0 Ireland

cbn

Collections

University of Galway Theses (PhD Theses)