The impact of prenatal dog keeping on infant gut microbiota development.

Introduction: Prenatal and early-life dog exposure has been linked to reduced childhood allergy and asthma. A potential mechanism includes altered early immune development in response to changes in the gut microbiome among dog-exposed infants. We thus sought to determine whether infants born into homes with indoor dog(s) exhibit altered gut microbiome development.

Methods: Pregnant women living in homes with dogs or in pet-free homes were recruited in southeast Michigan. Infant stool samples were collected at intervals between 1 week and 18 months after birth and microbiome was assessed using 16S ribosomal sequencing. Perinatal maternal vaginal/rectal swabs and stool samples were sequenced from a limited number of mothers. Mixed effect adjusted models were used to assess stool microbial community trajectories comparing infants from dog-keeping versus pet-free homes with adjustment for relevant covariates.

Results: Infant gut microbial composition among vaginally born babies became less similar to the maternal vaginal/rectal microbiota and more similar to the maternal gut microbiota with age-related accumulation of bacterial species with advancing age. Stool samples from dog-exposed infants were microbially more diverse (p = .041) through age 18 months with enhanced diversity most apparent between 3 and 6 months of age. Statistically significant effects of dog exposure on β-diversity metrics were restricted to formula-fed children. Across the sample collection period, dog exposure was associated with Fusobacterium genera enrichment, as well as enrichment of Collinsella, Ruminococcus, Clostridaceae and Lachnospiraceae OTUs.

Conclusion: Prenatal/early-life dog exposure is associated with an altered gut microbiome during infancy and supports a potential mechanism explaining lessened atopy and asthma risk. Further research directly linking specific dog-attributable changes in the infant gut microbiome to the risk of allergic disorders is needed.