Mother-to-infant transmission of intestinal bifidobacterial strains has an impact on the early development of vaginally delivered infant's microbiota

Abstract

Objectives: Bifidobacterium species are one of the major components of the infant's intestine microbiota. Colonization with bifidobacteria in early infancy is suggested to be important for health in later life. However, information remains limited regarding the source of these microbes. Here, we investigated whether specific strains of bifidobacteria in the maternal intestinal flora are transmitted to their infant's intestine.

Materials and methods: Fecal samples were collected from healthy 17 mother and infant pairs (Vaginal delivery: 12; Cesarean section delivery: 5). Mother's feces were collected twice before delivery. Infant's feces were collected at 0 (meconium), 3, 7, 30, 90 days after birth. Bifidobacteria isolated from feces were genotyped by multilocus sequencing typing, and the transitions of bifidobacteria counts in infant's feces were analyzed by quantitative real-time PCR.

Results: Stains belonging to Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium catenulatum, Bifidobacterium longum subsp. longum, and Bifidobacterium pseudocatenulatum, were identified to be monophyletic between mother's and infant's intestine. Eleven out of 12 vaginal delivered infants carried at least one monophyletic strain. The bifidobacterial counts of the species to which the monophyletic strains belong, increased predominantly in the infant's intestine within 3 days after birth. Among infants delivered by C-section, monophyletic strains were not observed. Moreover, the bifidobacterial counts were significantly lower than the vaginal delivered infants until 7 days of age.

Conclusions: Among infants born vaginally, several Bifidobacterium strains transmit from the mother and colonize the infant's intestine shortly after birth. Our data suggest that the mother's intestine is an important source for the vaginal delivered infant's intestinal microbiota.

Figure 1. Comparison of MLST profiles of strains obtained from 12 vaginal delivered mother-infant pairs.

Dendrogram of (A) 15 individual strains of B. adolescentis (ADO), (B) 25 individual B. bifidum strains (BIF), (C) 7 individual B. catenulatum strains (CAT), (D) 28 individual B. longum subsp. longum strains (LON), (E) 6 individual B. pseudocatenulatum strains (PSE) were all generated by a multi-scale setting for comparison and UPGMA for clustering. ^* Isolates from both members of a mother–infant pair and showing the same MLST profile within a given cluster.

Figure 2. Dendrogram of 22 individual B. longum subsp. longum isolates from 5 cesarean delivered mother-infant pairs.

All dendrogram were generated by a multi-scale setting for comparison and UPGMA for clustering.

Figure 3. The total bifidobacteria detected in 17 infant's feces from 0 to 7 days of age.

Numbers of vaginal delivered (VD) infants were 12, infants delivered by C-section (CS) were 5. Bars represent the median values respectively. For values less than the qPCR detection limit (10⁶ cells/g of feces), “detection limit/√2” was used as a complement value. Stars indicate significant differences between VD infants and CD infants (*P<0.05; **P<0.01).

Figure 4. The numbers of bifidobacteria in infants from 0 day to 7 days after birth.

Infant no.^a The B. adolescentis group consists of B. adolescentis genotypes A and B. ^b The B. catenulatum group consists of B. catenulatum and B. pseudocatenulatum.