Environmental, dietary, clinical factors linked to gut microbiota changes in infants

Different environmental and clinical factors, including caesarean delivery, early initiation of solids into the diet, and atopic dermatitis, contribute to gut microbiota maturity and diversity in infants, reports a recent study.

The researchers enrolled 288 exclusively breastfed infants, who participated in dietary randomized controlled trial from 3 months of age and contributed baseline samples, in this nested longitudinal analysis that looked at the 12-month evolution of the gut microbiota from faecal samples. Seventy participants provided follow-up samples.

At baseline, when infants were 3 months old, the gut microbiota was generally diverse. The most abundant microbial community genera were Bifidobacterium, Bacteroides, and multiple others belonging to the Firmicutes and Proteobacteria phyla.

Cluster analysis revealed three main groups: one dominated by Bifidobacterium, another by Bacteroides, and the final by Escherichia, Shigella, and other genera under the Firmicutes phylum. This three-cluster structure remained intact by 6 months of life but grew more focused on the Bacteroides-rich cluster by 12 months.

Among the environmental factors assessed, mode of delivery showed the strongest association with gut microbiota at baseline (p<0.01). Those who were born via caesarean section had an under-representation of the Bacteroides genus but nevertheless kept the three-cluster scheme. This suggested that other factors also contributed to the definition of microbial communities in infancy, the researchers explained.

Further investigations found other potentially impactful factors. Atopic dermatitis at age 12 months, for example, correlated with Clostridium sensu stricto and Haemophilus abundance at enrolment. Early introduction of allergenic foods also significantly affected the maturation of microbial communities, enriching them in genera under the Proteobacteria and Firmicutes phyla, particularly at age 6 months.