Antibacterial effect of bovine milk antibody against Escherichia coli in a mouse indigenous infection model.

A skim-milk fraction and a whey-protein concentrate (WPC) fraction were prepared from the cows that had been immunized with E. coli isolated from the mouse intestine. The antibacterial effect of these fractions against E. coli was examined. They contained antibody with a high affinity for E. coli strain 48, a representative strain in the mouse intestine, which is composed of a large amount of IgG and smaller amounts of IgA and IgM. Although these fractions showed no bactericidal or bacteriostatic activity against E. coli 48 directly in vitro, they exhibited strong agglutination and opsonization activities against the bacteria in vitro. The bacteria opsonized with the WPC fraction were taken up more effectively by liver macrophages in vivo, compared with unopsonized E. coli, after an intravenous injection into mice. Oral administration of the skim-milk fraction to mice significantly reduced the susceptibility to the lethal toxicity of 5-fluorouracil (5 FU). The increase in the population levels of E. coli in the intestinal tract after administration of 5 FU was inhibited by oral administration of the skim-milk fraction. These results strongly suggest that specific antibody may be effective in the prophylaxis against the indigenous infection with gram-negative bacteria such as E. coli after a period of chemotherapy in cancer patients.