Growth of bifidobacteria in mammalian milk

Microbial colonization of the mammalian intestine begins at birth, when from a sterile state a newborn infant is exposed to an external environment rich in various bacterial species. An important group of intestinal bacteria comprises bifidobacteria. Bifidobacteria represent major intestinal microbiota during the breast-feeding period. Animal milk contains all crucial nutrients for babies' intestinal microflora. The aim of our work was to test the influence of different mammalian milk on the growth of bifidobacteria. The growth of seven strains of bifidobacteria in human milk, the colostrum of swine, cow's milk, sheep's milk, and rabbit's milk was tested. Good growth accompanied by the production of lactic acid was observed not only in human milk, but also in the other kinds of milk in all three strains of Bifidobacterium bifidum of different origin. Human milk selectively supported the production of lactic acid of human bifidobacterial isolates, especially the Bifidobacterium bifidum species. The promotion of bifidobacteria by milk is species-specific. Human milk contains a key factor for the growth of specific species or strains of human-origin bifidobacteria compared to other kinds of milk. In contrast, some components (maybe lysozyme) of human milk inhibited the growth of Bifidobacterium animalis. Animal-origin strains of bifidobacteria were not able to significantly grow even in milk of animal origin, with the exception of B. animalis subsp. lactis 1,2, which slightly grew in sheep's milk.