Significance of fecal volatile fatty acids in shedding of Escherichia coli O157 from calves: experimental infection and preliminary use of a probiotic product.

Cattle have been recognized as a principal reservoir of Escherichia coli O157:H7. This organism appears to be confined to the gastrointestinal tract and is shed in feces. A probiotic product containing lactic acid-producing Streptococcus bovis LCB6 and Lactobacillus gallinarum LCB 12 isolated from adult cattle was developed, and a preliminary experiment was conducted to evaluate its effect on the elimination of E. coli O157 from experimentally infected calves. Eight 4-month-old Holstein calves were orally challenged with E. coli O157 and the probiotic product was administered against four calves continued fecal shedding of E. coli O157 by the 7th day after infection. Fecal shedding of E. coli O157 was completely inhibited and re-shedding was not detected in any of the animals. Remarkable increase of VFAs, especially that of acetic acid in feces after the administration of probiotic bacteria correlated with the diminution of E. coli O157. Four calves that had spontaneously ceased fecal shedding of E. coli O157 by the 7th day exhibited a high concentration of VFAs in feces before and after experimental infection. Although our results are preliminary and obtained from calves under limited conditions, the possible application of probiotic product to reduce fecal shedding of E. coli O157 from cattle is suggested.