Mixed Evidence for Impact of Early Infant Gut Microbiome and Later Development of Autism Spectrum Disorder in the MARBLES Prospective Cohort Study.

This study investigated the relationship between early infant gut microbiome composition and subsequent neurodevelopmental outcomes. Fecal samples from children in the markers of autism risks in babies-learning early signs (MARBLES) study, a cohort with elevated likelihood of autism, were collected between 0 and 7 months of age and analyzed using 16S rRNA sequencing to evaluate whether the gut microbial composition during early infancy is associated with later neurodevelopmental diagnoses. Clinical classification as autism spectrum disorder (ASD), non-typically developing without ASD (non-TD), or typically developing (TD) was completed around 36 months of age using gold-standard assessment tools. Overall, no significant differences in alpha diversity or beta diversity, nor any differentially abundant bacterial taxa, were found between groups of infants who developed ASD or non-TD compared to those who went on to have TD. Nonetheless, our findings highlight some early differences in gut microbial composition during infancy that may relate to later neurodevelopmental outcomes. Before adjusting for multiple comparisons, infants who later developed ASD had slightly lower levels of Veillonella and Flavonifractor genera compared to children who were later found to be TD. These results suggest specific bacterial taxa may already differentiate in early infancy, but may be more subtle than other factors, such as mode of delivery and diet during early infancy. To understand longitudinal trajectories of the gut microbiome in association with later neurodevelopment, future studies should include a larger cohort to detect smaller effect sizes or investigate later time points in infancy.