Galactooligosaccharide supplementation provides protection against Citrobacter rodentium-induced colitis without limiting pathogen burden.

Many enteric pathogens, including Salmonella and enteropathogenic and enterohemorrhagic Escherichia coli, express adhesins that recognize and bind to carbohydrate moieties expressed on epithelial cells. An attractive strategy for inhibiting bacterial adherence employs molecules that mimic these epithelial binding sites. Prebiotic oligosaccharides are non-digestible, fermentable fibres capable of modulating the gut microbiota. Moreover, they may act as molecular decoys that competitively inhibit adherence of pathogens to host cells. In particular, galactooligosaccharides (GOS) and other prebiotic fibres have been shown to inhibit pathogen adherence to epithelial cells in vitro. In the present study, we determined the ability of prophylactic GOS administration to reduce enteric pathogen adherence both in vitro and in vivo as well as protect against intestinal inflammation. GOS supplementation significantly reduced the adherence of the epithelial-adherent murine bacterial pathogen Citrobacter rodentium in a dose-dependent manner to the surface of epithelial cells in vitro. A 1- to 2-log reduction in bacterial adherence was observed at the lowest and highest doses tested, respectively. However, mouse studies revealed that treatment with GOS neither reduced the adherence of C. rodentium to the distal colon nor decreased its dissemination to systemic organs. Despite the absence of adherence inhibition, colonic disease scores for GOS-treated, C. rodentium-infected mice were significantly lower than those of untreated C. rodentium-infected animals (P=0.028). Together, these data suggest that GOS has a direct protective effect in ameliorating disease severity following C. rodentium infection through an anti-adherence-independent mechanism.