Effect of fiber source on short-chain fatty acid production and on the growth and toxin production by Clostridium difficile.

BACKGROUND

Fermentable fiber promotes the growth of resident gut microbes, which modify the environment of the gastrointestinal tract and thus prevent colonization by Clostridium difficile.

METHODS

An in vitro system with pigs as fecal inoculum donors was used to estimate fiber fermentability and changes in intestinal microbiota.

RESULTS

Acetate and propionate production (mumol/mg substrate fermented/day) was greatest for gum arabic (1013.4 and 704.1, respectively); butyrate production was greatest for xylo-oligosaccharide (345.6). Growth of total anaerobes and clostridia was greatest for gum arabic (21.2 and 16.2 x 10(8) counts/ml, respectively) and xylo-oligosaccharides (21.0 and 19.6 x 10(8) respectively); growth of acidogenic bacteria was greatest with fructo-oligosaccharide (6.7 x 10(8) counts/ml). No culturable counts of C. difficile were obtained, nor was toxin A detected.

CONCLUSIONS

Fermentable fibers support the growth of indigenous intestinal bacteria, particularly acidogenic bacteria, and yield large amounts of short-chain fatty acids with decreased gut pH. These factors contribute to the prevention of growth and toxin elaboration by C. difficile.