Oral and Gut Microbiota in Individuals With Autism Spectrum Disorder: A Pilot Case–Control Study

BACKGROUND: Recent studies suggest that gut microbiota play important roles in individuals with autism spectrum disorder (ASD), potentially influencing the development and severity of the condition. Oral bacteria may be directly or indirectly involved in the biological and symptomatic aspects of ASD through their effect on gut microbiota. AIM: This pilot study aimed to characterise compositional alterations in the oral and gut microbiota of individuals with ASD and to identify bacterial taxa in saliva and faeces that may serve as potential microbial indicators of ASD. DESIGN: Salivary and faecal samples were collected from 10 individuals with ASD and 10 typically developing controls. The oral and gut microbiota were evaluated using 16S ribosomal RNA marker-gene sequencing. RESULTS AND CONCLUSION: Distinct features of the oral and gut microbiota were identified that differed between individuals with ASD and typically developing controls. Based on linear discriminant analysis effect size, the relative abundances of the genera Neisseria were higher in the oral microbiota of the ASD groups, whereas the genera Faecalibacterium were enriched in the gut microbiota. These findings highlight the potential relevance of the oral-gut-brain axis in ASD. Additionally, non-invasive sampling of saliva and faeces may be utilised for early ASD screening.