Baby-to-baby transmission shapes the infant gut microbiome

What the study found: Baby-to-baby transmission of gut microbes was extensive during the first year of nursery attendance, and nursery-acquired strains made up a share of the infant gut microbiome comparable to that from family by the end of the first term.
Why the authors say this matters: The authors conclude that social interactions in infancy are crucial drivers of infant microbiome development, and the study suggests that transmission between babies is an important part of that process.
What the researchers tested: The researchers carried out a metagenomic survey, which uses DNA sequencing of microbial communities, in nursery settings across three facilities. They followed 134 individuals, including babies, educators, and families, and collected 1,013 fecal samples over the first year of nursery attendance to track strain transmission within and between nursery groups.
What worked and what didn't: The study detected extensive transmission within nursery groups after only 1 month of nursery attendance. Transmission continued to increase over the nursery year, with single strains spreading in some classes and with multiple baby-acquisition and species-transmissibility patterns. Having siblings was associated with higher microbiome diversity and reduced strain acquisition from nursery peers, while antibiotic treatment accounted most for increased influx of strains.
What to keep in mind: The abstract does not describe specific limitations beyond the study being carried out in nursery settings over the first year of attendance, so the summary is limited to that scope.

Key points

• Baby-to-baby gut microbiome transmission was extensive during the first year of nursery attendance.
• By the end of the first term, nursery-acquired strains contributed about as much as family-derived strains to the infant gut microbiome.
• Transmission increased over the nursery year, with complex strain-spreading patterns across classes.
• Having siblings was associated with higher microbiome diversity and less strain acquisition from nursery peers.
• Antibiotic treatment was the condition most associated with increased influx of strains.