Introduction It has long been thought that dietary fibre promotes intestinal health and we have previously shown that the soluble non-starch polysaccharide (NSP) from plantain bananas (Musa spp.) can inhibit the epithelial adhesion and microfold (M)-cell translocation of Crohn's-associated Escherichia coli (Gut 2010;59:1331–9) and a range of diarrhoeal pathogens including Salmonella and Shigella (Gut 2011;60:A96). Here we examined NSP from representative examples of monocotyledon and dicotyledon plant fibres, for efficacy to inhibit epithelial interactions of Clostridium difficile, a major cause of antibiotic associated diarrhoea, and enterotoxigenic E coli (ETEC), the commonest cause of traveller's diarrhoea.

Methods Human intestinal epithelial cell-line Caco2-cl1 cell monolayers were pre-treated for 30 min with NSP preparations, including those from vegetable (broccoli, leek), fruit (plantain, apple) and cereal (oat) sources, followed by infection with C. difficile (for 2 h, at multiplicity of infection MOI of 100) or ETEC (4 h; MOI 100). In parallel experiments, adherence of bacteria to cell monolayers was examined following fixation, Giemsa stain and light microscopy.

Results C difficile adhesion to Caco2-cl1 cells was significantly inhibited in the presence of broccoli, leek and plantain NSP. Leek NSP, at 5 mg/ml, had the most significant effect on inhibition of C difficile adhesion (54.9±9.7% reduction) compared to untreated controls (n=3−9, p<0.001, ANOVA). Neither apple nor oat NSP had any significant ability to prevent C difficile adhesion to CaCo2-cl1 cells. ETEC adhesion to CaCo2-cl1 cells was also significantly inhibited in the presence of leek NSP (53.7±13.6%; p<0.01) and plantain NSP (40.9±9.3%; p<0.001) but no efficacy was observed for soluble broccoli, apple nor oat fibre. Blockade of adherence to Caco2-cl1 cells by NSP was also confirmed by Giemsa stain.

Conclusion Leek, plantain and/or broccoli NSP show efficacy at blocking C difficile and ETEC adhesion in a dose dependent manner to the intestinal epithelium in vitro and at concentrations readily achievable in vivo. The close proximity of C difficile and ETEC to the host epithelium is almost certainly essential for the release of their respective toxins and the exertion of their pathogenic effect. Disruption of bacterial-epithelial adherence to the intestinal mucosa by soluble plant fibres may therefore be of therapeutic benefit.

Competing interests H Simpson grant/research support from: industrial case studentship with support from Provexis plc, C Roberts conflict with: past employee of Provexis plc, J Rhodes consultant for: is a member of advisory boards for Atlantic, Procter and Gamble and Falk, speaker bureau with: Has received speaking honoraria from Abbott, Falk, Ferring, Glaxo Smith Kline, Procter and Gamble, Schering Plough, Shire and Wyeth, Conflict with: holds a patent with the University of Liverpool and Provexis UK for use of a soluble fibre preparation as maintenance therapy for Crohn's disease plus a patent pending for its use in antibiotic-associated diarrhoea, B Campbell grant/research support from: grant support from Provexis plc and the Bo & Vera Ax:son Johnson Foundation Ltd.