In vitro antagonism of Escherichia coli by piglet small intestinal bacteria isolated by selective enrichment in media containing sow colostrum, piglet feed or brain heart infusion.

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Abstract
The effect of media composition on the selection of different components of a mixed microbial population during serial transfer was examined. The initial microbial populations were from the small intestinal contents of 3- and 8-day-old piglets. Selection in brain-heart infusion broth was compared with selection in media based on piglet diets, either piglet feed infusion or sow colostrum. Clostridium and Lactobacillus were the predominant organisms isolated from media prepared from sow colostrum and piglet feed, although the microflora from piglet feed infusion broth was more varied and complex. Lactobacillus and non-hemolytic Escherichia coli were the predominant organisms identified from brain-heart infusion broth. Nearly half (48%) of the microflora from brain-heart infusion broth originally inoculated with intestinal fluid from an 8-day-old piglet consisted of non-hemolytic E. coli. E. coli were not detected after serial transfer in either sow colostrum or piglet feed infusion broths. Absence of E. coli was attributed in part to the presence of inhibitory substance(s) in sow colostrum and piglet feed infusion broths and in part to the presence of organisms antagonistic to E. coli. Bifidobacterium A, Clostridium F, and Lactobacillus F, which comprised 24% of the isolates obtained after serial transfer in sow colostrum broth, were antagonistic toward E. coli as well as were Bifidobacterium C, Lactobacillus G, and Leptotrichia A, which accounted for 38% of the isolates obtained after serial transfer in piglet feed infusion broth.