Molecular genetic study of species and strain variability in bifidobacteria population in intestinal microflora of breast-fed infants and their mothers.

Qualitative and quantitative composition of enteric bifidoflora was studied in a group of 13 mother-infant pairs. Pure cultures of Bifidobacterium strains were isolated from feces and their species were identified by PCR with species-specific primers or by partial sequencing of 16S rDNA. The strains were compared by REP-PCR. The most incident Bifidobacterium species in mothers were B. longum and B. adolescentis. The infants were mainly colonized by B. bifidum and B. longum. The mother and her baby were colonized by the same Bifidobacterium species in 9 of 13 cases. In 5 (38.5%) of these cases, these pairs of strains were identical by their REP-PCR profiles. These strains belonged to B. longum in one case, B. bifidum in 3 cases, and B. adolescentis in 1 case. Our results support the hypothesis on early colonization of infants with maternal bifidobacterium strains.