After 4 months in the nursery, the babies’ microbiota resembles that of their peers more than that of their family members: a wealth of diversity destined to last.
Parents discouraged by their children’s many days of illness in the first year of nursery school will be happy to know that children who attend nursery schools have a microbiota that is much richer in bacterial strains than those who do not attend them, thanks to the continuous interactions and exchanges (seasoned with mucus and saliva) with their peers.
According to a study by the University of Trento published in Naturealready after a month of attending nursery school, a significant portion of children’s intestinal bacteria derives from those of their classmates. After 4 months, the babies already share 15-20% of intestinal bacterial species with their companions, a larger portion of the microbiota than that acquired by family members after birth.
A very rapid contamination
It is thought that the microbiota of newborns begins to form during birth, thanks to the contribution of the mother’s bacteria, and is therefore enriched by the bacterial strains of close family members. To understand what happens later, with the first extra-familial interactions with peers, a group of microbiologists led by Nicola Segata analyzed the stool samples of 43 children with a median age of 10 months at the beginning of the study, as well as those of 10 members of the nursery staff and many family members of the children including mothers, fathers, brothers and sisters and pets.
The collection began from the first day of nursery school, to capture the moment of greatest susceptibility to contamination, given that the children’s immune systems were still immature, and continued weekly until the Christmas holidays (but for a small group of children until July).
Round trip
The diversity of the children’s microbiota was enriched already after the first month, and continued to do so for the entire school year. The home environment certainly influenced everyone’s contribution to these “exchanges”: those who had brothers or sisters generally received more microorganisms from them than from their parents and had a richer microbiota – therefore they tended to acquire fewer bacterial strains from their classmates.
In children with dogs and cats at home, cases of exchange of intestinal microorganisms with animals have been noted, interactions that did not emerge in adults – as if there were more intimate contacts between small children and quadrupeds.
A curious fact is that the children in the nursery have sometimes acted as intermediaries for exchanges of bacteria between their respective parents.
A symbiont of the human intestine, the “good” bacterium Akkermansia muciniphilait is passed from a mother to her baby, from this to a nestmate and from the baby to both parents. A… journey that could help to better understand not only the influences on the microbiota, but also the spread of pathogens between the family context and the external one.
Let’s repopulate!
A positive effect of this sociability emerged when some of the children had to take antibiotics. The treatment dramatically reduced the diversity of their microbiota, but contact with peers allowed the intestinal environment to be rapidly repopulated with beneficial species.
According to the researchers, it is unclear what the long-term health impacts of this early enrichment are; But the fact that most of the acquired bacterial strains were still present a year after the first day of school in most of the children in the follow-up study suggests that those strains may remain established into adulthood. In memory of those first days spent among friends.
