The ability of enteric diarrhoeal pathogens to ferment starch to short-chain fatty acids in vitro.

BACKGROUND

Short-chain fatty acids (SCFA), produced in the normal colon by bacterial fermentation, are decreased in acute diarrhoea. This may have deleterious effects on epithelial function in the colon.

METHODS

The ability of several diarrhoeal pathogens to produce SCFA when incubated with starch in vitro was studied. Isolated pathogens were incubated for 24 h with either no added substrate, glucose, or starch under anaerobic conditions, and SCFA were quantitated by gas-liquid chromatography.

RESULTS

Unlike the normal colonic flora, the pathogens produced acetate but not propionate or butyrate. D-Lactate was also produced by all the pathogens studied. When the pathogens were incubated in anaerobic medium containing starch, significantly greater amounts of acetate and significantly lesser amounts of lactate were produced.

CONCLUSIONS

The inability of enteric pathogens to produce butyrate may impair epithelial cell function, whereas production of D-lactate may enhance mucosal damage in diarrhoeal disease. The presence of luminal starch may be helpful in shifting the fermentation profile to a more favourable pattern.