Exploring Vertical Transmission of Bifidobacteria from Mother to Child

Abstract

Passage through the birth canal and consequent exposure to the mother's microbiota is considered to represent the initiating event for microbial colonization of the gastrointestinal tract of the newborn. However, a precise evaluation of such suspected vertical microbiota transmission has yet to be performed. Here, we evaluated the microbiomes of four sample sets, each consisting of a mother's fecal and milk samples and the corresponding infant's fecal sample, by means of amplicon-based profiling supported by shotgun metagenomics data for two key samples. Notably, targeted genome reconstruction from microbiome data revealed vertical transmission of a Bifidobacterium breve strain and a Bifidobacterium longum subsp. longum strain from mother to infant, a notion confirmed by strain isolation and genome sequencing. Furthermore, PCR analyses targeting unique genes from these two strains highlighted their persistence in the infant gut at 6 months. Thus, this study demonstrates the existence of specific bifidobacterial strains that are common to mother and child and thus indicative of vertical transmission and that are maintained in the infant for at least relatively short time spans.H uman beings may be considered superorganisms that consist of both eukaryotic and prokaryotic cells (1). It is generally accepted, not only that the nuclear and mitochondrial genomes are transferred to the next generation, but that such transfer may also include certain members and associated genomes of the symbiotic community, whose microbial genes outnumber those of the eukaryotic host by over 100-fold (2). Passage through the birth canal, together with breastfeeding, represents a very important opportunity for transfer of symbionts from one generation to the next. Notably, this transmission is facilitated by the maternal holobiont, i.e., the organism, together with its associated microbial communities, and the mother is both actively and passively engaged in providing a symbiotic and perhaps long-lasting microbial community to her offspring. However, each individual develops a specific microbial community by adulthood, suggesting that stochastic colonization is more important than direct vertical transmission. In fact, while individual strains may be directly transmitted, the majority of the long-lasting community is probably not. In mammals, it is generally accepted that the fetus develops in an essentially sterile environment within the amnion and that bacterial colonization of the fetus is made possible as soon as the amnion breaks prior to its delivery through the birth canal (3). Bifidobacteria are among the first bacterial colonizers of the human gut and have been subject to extensive scientific scrutiny (4, 5). It has become clear that certain species of the genus Bifidobacterium, e.g., Bifidobacterium breve and Bifidobacterium bifidum, are genetically adapted to colonize the infant gut (for a review, see reference 6). Such bacteria have evolved genetic strategies that allow them to metabolize particular glycans present in human ...

Exploring the role of the microbiota member Bifidobacterium in modulating immune-linked diseases

“…Current studies indicate that bifidobacteria are transmitted vertically from the mother's vagina, GI tract, or breast milk. This is supported by findings by Duranti et al [22], who used a novel internal transcribed spacer (ITS) approach trialled previously [23]. Duranti et al found genomically identical bifidobacteria strains in faecal and milk samples from 24 mother-infant pairs.…”

Microbial strain-level population structure and genetic diversity from metagenomes

“…It will be similarly crucial to associate the presence of strains or subclades of microbial species with immune or chronic disease phenotypes even in the absence of acute infection. The same types of approaches can also start to unravel how members of the microbiome without overt phenotypes are transmitted among hosts, e.g., in vertical mother-to-infant transmission (Milani et al 2015;Asnicar et al 2017) or horizontal orofecal routes . This is of particular interest in the context of interventions such as probiotics or fecal microbiome transplants, in which strain tracking is necessary to identify successful receipt or engraftment of the intended microbes (Li et al 2016).…”

Genomics of the Genus Bifidobacterium Reveals Species-Specific Adaptation to the Glycan-Rich Gut Environment

“…Only very recently, a study based on analysis of the gut microbiota of mothers and corresponding children by a combination of amplicon-based profiling and shotgun metagenomics demonstrated that mother and child share particular bifidobacterial strains, belonging to Bifidobacterium breve and Bifidobacterium longum subsp. longum, which is thus indicative of vertical transmission (11,12). Mode of delivery (i.e., vaginally delivered versus delivered by cesarean section) and type of nutrition (i.e., breast-fed versus bottle-fed) are considered to be important factors that provide differential colonization opportunities, thereby impacting the composition of the neonatal gut microbiota, including the colonization level and species composition of bifidobacteria (13,14).…”