Multilocus sequence typing of bifidobacterial strains from infant’s faeces and human milk: are bifidobacteria being sustainably shared during breastfeeding?

Abstract

Bifidobacteria are considered to be one of the most important beneficial intestinal bacteria for infants, contributing to the priming of the mucosal immune system. These microbes can also be detected in mother's milk, suggesting a potential role of human milk in the colonisation of infant's gut. However, little is known about the timing of bacteria appearance in human milk, and whether human milk is the first source of inoculation. Here, we investigated whether specific strains are shared sustainably between maternal milk and infant's gut. Faecal samples and human milk were collected from 102 healthy mother-infant pairs (infant's faeces: meconium, 7, 30 days of age; mother's milk: once before delivery, colostrum, 7, 30 days after delivery). Bifidobacterial strains were isolated from these samples, and were discriminated by means of multilocus sequencing typing. No bifidobacteria were detected from human milk collected before delivery, or colostrum. Strains were isolated only from human milk samples obtained 7 days after birth or later. On the other hand, bifidobacterial strains were obtained from infant's faeces throughout the study period, sometimes as early as the first day of life (meconium). We have found that bifidobacterial species belonging to Bifidobacterium bifidum, Bifidobacterium breve, and Bifidobacterium longum subsp. longum could be identified as monophyletic between infant's faeces and their mother's milk. These strains were confirmed to be sustainably shared between maternal milk and infant's gut. Moreover, monophyletic strains were isolated at the same time point or earlier from infant's faeces than from human milk, and none were isolated earlier from human milk than from infant's faeces. Although it remains unclear whether human milk is the first source of microbes for infants, our results confirm that human milk is a reservoir of bifidobacteria, and specific strains are shared between infant's intestine and human milk during breastfeeding.

Maternal inheritance of bifidobacterial communities and bifidophages in infants through vertical transmission

“…Transmission of (bifido)bacteria from mother to her child may be possible through ingestion of mother’s milk [38, 39, 43, 44]. This human fluid represents a bacterial transmission medium that is ideal not only for microbiota dispersal but also for the provision of nutrients to the initial colonizers of the infant gut [10, 38, 39, 44, 45].…”

“…This human fluid represents a bacterial transmission medium that is ideal not only for microbiota dispersal but also for the provision of nutrients to the initial colonizers of the infant gut [10, 38, 39, 44, 45]. Human milk is a very rich source of glycans, including lactose and human milk oligosaccharides (HMOs) [46], which represent an important carbon and energy source for pioneering saccharolytic members of the infant gut microbiota, in particular bifidobacteria [47–49].…”

Does the maternal vaginal microbiota play a role in seeding the microbiota of neonatal gut and nose?

“…Contrary to expectations, the resemblance in community membership between infant and mother stool microbiota for unrelated mothers was greater than resemblance to the microbiota of own mother. This is surprising, because the presence of identical strains of bifidobacteria strains in both maternal and infant stool was shown using culture and typing methods (Jost et al, 2013;Makino et al, 2015). Re-analysis using a large study of 100 Swedish infants and a shotgun metagenomics approach (Bäckhed et al, 2015;Nayfach et al, 2016), may help to explain this counterintuitive result.…”

Obesity and overweight: Impact on maternal and milk microbiome and their role for infant health and nutrition

“…Bifidobacterium group is more frequent in breastfed but other compositions are also common. Among breastfed infants, the maternal transmission of specific intestinal bacterial strains has been described [99][100][101], supporting the maternal microbial transfer hypothesis and suggesting unique family-specific strains in each mother-infant dyad. Additionally, human milk contains milk glycans such as oligosaccharides, glycoproteins, and glycolipids, which have also been recognised as modulators and drivers of infant microbiota development that promote the growth and activity of specific bacterial populations, in particular Bifidobacterium and Bacteroides spp.…”