Inhibitory activity of gut bacteria against Escherichia coli O157 mediated by dietary plant metabolites.

Under both aerobic and anaerobic conditions, the growth of Escherichia coli O157 strain NCTC 12,900 was inhibited by the coumarins esculetin, umbelliferone and scopoletin, but not by the coumarin glycoside esculin. Esculin-hydrolysing bacteria from the rumen, the pig gut and the human gut inhibited growth of E. coli in an overlay-plate assay in the presence of esculin. The combined effect of esculetin and volatile fatty acids was greater than the effect of either factor alone suggesting that coumarin glycosides in the diet might reduce the growth or survival of E. coli O157 in the gut. Adding esculin to incubations of mixed rumen contents significantly reduced the survival of E. coli O157.