Abstract
Dietary fibers have well-known beneficial effects on human health, but their anti-infectious properties against human enteric pathogens have been poorly investigated. Enterotoxigenic Escherichia coli (ETEC) is the main agent of travelers’ diarrhea, against which targeted preventive strategies are currently lacking. ETEC pathogenesis relies on multiple virulence factors allowing interactions with the intestinal mucosal layer and toxins triggering the onset of diarrheal symptoms. Here, we used complementary in vitro assays to study the antagonistic properties of eight fiber-containing products from cereals, legumes or microbes against the prototypical human ETEC strain H10407. Inhibitory effects of these products on the pathogen were tested through growth, toxin production and mucus/cell adhesion inhibition assays. None of the tested compounds inhibited ETEC strain H10407 growth, while lentil extract was able to decrease heat labile toxin (LT) concentration in culture media. Lentil extract and specific yeast cell walls also interfered with ETEC strain H10407 adhesion to mucin beads and human intestinal cells. These results constitute a first step in the use of dietary fibers as a nutritional strategy to prevent ETEC infection. Further work will be dedicated to the study of fiber/ETEC interactions within a complex gut microbial background.
Highlights
When Enterotoxigenic Escherichia coli (ETEC) bacteria were grown in Luria Bertani (LB)-rich medium (Figure 1A), no statistical difference was observed between each fiber-supplemented condition and the negative control according to Dunnett’s multiple comparisons test
We evaluated the effect of lentil extracts on pure labile toxin (LT) toxin solutions and showed that the inhibitory effect was partially conserved but not significant at the dose of 2 g·L−1 of fiber used in this study
By using a mucin-bead adhesion assay we demonstrated that lentil extracts and yeast cell walls could decoy the ETEC strain H10407 from mucus polysaccharides adhesion
Summary
Most of the dietary fibers consumed by humans are of plant origin, but some of them are derived from animals, fungi or bacteria [2]. They have a well-known beneficial health effect in humans, such as transit regulation, slowing down of glucose absorption, immune system modulation and support of gut microbiota diversity [3,4]. Insoluble dietary fiber particles have even been recently shown to constitute a microbiota niche on their own [5,6] Another understudied effect of dietary fibers is their ability to prevent enteric infections [7]. Scarce in vitro studies have already shown the antagonistic properties of fibers against various enteric bacterial pathogens, mostly through a direct bacteriostatic effect, anti-adhesion properties on intestinal cells [8,9,10,11] or a decoy for pathogen/toxin binding to mucosal polysaccharides [12,13,14,15]
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