Abstract
BACKGROUND: Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder impairing social and communication skills. Gut microbiota has become key in understanding ASD pathophysiology. However, the relationship between the ASD symptoms and alternation of gut microbiota still remains unknow. We hypothesize that the composition of gut microbiota in children with ASD may be strongly associated with the severity of their symptoms. METHODS: Here, fecal samples from children (divided in to three groups: neurotypical, severe ASD and mild ASD) at a hospital were collected. The symptoms of ASD were assessed by an experienced pediatric neurologist, and the severity of the symptoms in children with ASD was determined based on the assessment scores. Then the diversity and composition of gut microbiota were detected by high-throughput sequencing. RESULTS: In total, 2,021 amplicon sequence variants (ASVs) were obtained from 46 fecal samples, with highest in the neurotypical group. Alpha diversity in bacteria differed between severe and mild ASD. Microbiota health and dysbiosis indices varied with ASD severity. Beta diversity indicated that severe ASD differed from others, and mild ASD was closer to neurotypical in community structure. At the phylum level, Firmicutes was the dominant bacteria but abundances differed in different groups, and Ascomycota increased in severe ASD fungi. At the genus level, groups had distinct dominants, and mild ASD microbiota resembled that of neurotypical children. Function prediction revealed differences in bacteria and fungi, with severe ASD having higher amino acid metabolism, lower cofactor/vitamin metabolism, and more undefined saprotrophs. CONCLUSION: This study revealed gut microbiota differences between ASD children (varying symptoms) and neurotypical ones, showing milder ASD closer in microbiota aspects. It offers insights for exploring ASD pathogenesis and devising interventions.