Factors affecting the growth of bifidobacteria in human milk

Five strains of bifidobacteria of human origin and 2 strains of bifidobacteria of animal origin were tested for growth in 10 samples of human milk. Growth of Bifidobacterium bifidum in human milk was accompanied by a decrease in pH and production of acids. The number of viable cells of Bifidobacterium animalis was decreased from 6 log cfu mL−1 to 3 log cfu mL−1 after incubation in human milk. There were significant differences (P < 0.05) between bacterial counts of B. bifidum and B. animalis in milk samples tested. Resistance to lysozyme and the ability to utilise human milk oligosaccharides (HMOs) were identified as the most important factors affecting the growth of bifidobacteria in human milk. Four out of 5 strains of human origin were resistant to lysozyme and utilised HMOs. In contrast, B. animalis was susceptible to lysozyme and did not utilise HMOs.