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.
All of the Salmonella enteritidis strains isolated from diseased animals (61 strains) and from beef (2 strains) in Japan and in West Germany (1 strain), except for 2 strains isolated from ducks, harbored either a 36-megadalton (Md) plasmid alone or in combination with several other plasmids of different sizes. It is likely that these 36-Md plasmids from various S. enteritidis strains were derived from the same origin because their plasmid DNAs showed the same cleavage patterns obtained with EcoRI, HindI, and BamHI. We also suggested that this plasmid is native to S. enteritidis. Tests carried out on two strains isolated from ducks which naturally lacked this plasmid and one strain whose plasmid was artificially cured showed that the strains without the 36-Md plasmid showed less virulence compared to a wild-type strain harboring the 36-Md plasmid, suggesting that this 36-Md plasmid might be associated with virulence for mice.
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