The nasal microbiome in early infancy is primarily shaped by the maternal nasal microbiome

The infant nasal microbiota closely mediates the risks of developing childhood respiratory diseases. However, the primary sources of these early residing bacteria remain largely unknown, preventing the development of microbiome strategies for disease prevention.

Our aim was to identify the primary maternal source of bacteria found in the early infant nasal microbiome.

We conducted a birth cohort study titled the Mother Infant Microbiome International Cohort (MIMIC) study. We recruited 95 mother-newborn dyads from 3 sites (St Louis, Mo; San Juan, Puerto Rico; and Accra, Ghana) and collected samples at 2 time points (at the infants' birth and when they were around 2 months old). We performed analyses of 16S ribosomal RNA gene sequencing data to evaluate the maternal microbiomes (nasal, saliva, breast milk, and areola skin) as sources seeding the infant nasal microbiome.

The infant nasal microbiome underwent a major compositional change during the first 2 months of life. The maternal nasal microbiome was identified as the primary source of bacteria in the early nasal microbiome across the 3 study regions. Corynebacterium was predominantly transferred from the maternal nasal microbiome. Infants were more likely to harbor a Corynebacterium-dominant nasal microbiome if the nasal microbiome of their mother was Corynebacterium dominant.

The maternal nasal microbiome is an important source of bacteria in the early nasal microbiome. A large portion of transmitted bacteria from the maternal nasal microbiome belonged to the generally beneficial bacterial genus Corynebacterium. The results from this study will aid in the development of early-life intervention strategies aimed at reducing the incidence of childhood respiratory diseases and asthma.