Inter-species differences in the growth of bifidobacteria cultured on human milk oligosaccharides.

Human milk (HM) contains as the third most abundant component around 200 different structures of human milk oligosaccharides (HMOs). HMOs are the first and irreplaceable prebiotics for infants, supporting bifidobacteria as the most important bacterial group in an infant intestine. The aim of our study was to test the growth of bifidobacteria in HM and on HMOs. Bifidobacteria were isolated from two groups of infants. The first one (eight strains) were isolated from infants who had bifidobacteria in their feces but, after a short period of time (4 to 24 days), bifidobacteria were no longer detected in their feces (disappeared bifidobacteria [DB]). The second group of bifidobacteria (eight strains) originated from infants with continual presence of bifidobacteria in their feces (persistent bifidobacteria [PB]). There were significant differences (p < 0.05) between DB and PB groups in the ability of the strains to grow in HM. PB grew in HM, reaching counts higher than 7 log CFU/ml. In contrast, counts of DB decreased from 5 to 4.3 log CFU/ml after cultivation in HM. The final pH after cultivation of bifidobacteria on HMOs was 6.2 and 4.9 in DP and PB groups, respectively. In general, Bifidobacterium bifidum and B. breve species were able to utilize HMOs, while B. adolescentis and B. longum subsp. longum species did not. The ability to grow in HM and to utilize HMOs seem to be important properties of bifidobacteria which are able to colonize infant intestinal tract.