Sa1276 Altered Mucus Oligosaccharide Composition in Human C. difficile Infection

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Introduction: Clostridium difficile infection (CDI) represents an increasing public health problem as it is a primary cause of antibiotic-induced diarrhea and colitis. In the United States, CDI affects millions of patients each year and represents an annual cost of over $1 billion. A more in-depth understanding of C. difficile colonization is necessary to improve therapeutics. In C. difficile pathogenesis, antibiotic disruption of the gut microbiota provides an open niche and invading C. difficile enters a colonization phase, which includes bacterialhost interaction, mucus adhesion and toxin production. Mucus oligosaccharides serve as both a fuel source and as binding sites for a number of bacteria. Previous studies have demonstrated that C. difficile is unable to cleave terminal mucus oligosaccharides. We hypothesize that an altered gut microbiota in CDI patients cleaves terminal mucus oligosaccharides exposing/producing bacterium and toxin binding sites. Furthermore we hypothesize that cleaved oligosaccharides can be foraged by C. difficile and used for proliferation. Methods& results: CDI patients presented with increased Bacteroidetes and decreased Firmicutes stool microbiota. In addition, CDI biopsies exhibited decreased N-acetylgalactosamine and increased terminal galactose mucus oligosaccharides. Terminal galactose residues have been shown to be the toxin A binding site in animal models, but lack of terminal galactose residues in the human colon have led to the hypothesis that the toxin A receptor must be different in humans. Our data indicates that terminal galactose residues may represent the human toxin A receptor which is upregulated in CDI. No changes were observed in mucus fucose or mannose levels. CDI patients did present with decreased mucus MUC2, with no changes in MUC1. These data demonstrate a unique mucus oligosaccharide composition in CDI patients. In vitro C. difficile BAA-1870 had enhanced binding to mucus extracted from CDI patients compared to healthy patient mucus, indicating the presence of an alternative binding epitope in the mucus of CDI patients. Furthermore, C. difficile BAA-1870 grown in TYGwas able to use fucose,mannose, galactose, N-acetylgalactosamine, N-acetylglucosamine, and sialic acid oligosaccharides for growth, although growth varied depending on pH and Na.Conclusions: These data demonstrate that CDI patients exhibit an altered gut microbiota with corresponding altered mucus oligosaccharide and MUC2 composition. In vitro C. difficile is capable of using multiple oligsoaccharides for growth which may represent a factor in the colonization phase.