Oral microbiota in autistic children: Diagnosis-related differences and associations with clinical characteristics

Similar to the gut microbiome, oral microbiome compositions have been suggested to play an important role in the etiology of autism. However, empirical research on how variations in the oral microbiome relate to clinical-behavioral difficulties associated with autism remains sparse. Furthermore, it is largely unknown how potentially confounding lifestyle variables, such as oral health and nutrition, may impact these associations. To fill this gap, the current study examined diagnosis-related differences in oral microbiome composition between 80 school-aged autistic children (8-12 years; 64 boys, 16 girls) versus 40 age-matched typically developing peers (32 boys, 8 girls). In addition, associations with individual differences in social functioning (SRS-2), repetitive behavior (RBS-R) and anxiety (SCARED) were explored, as well as the impact of several lifestyle variables regarding nutrition and oral health. Results provide important indications that the bacterial genera Solobacterium, Stomatobaculum, Ruminococcaceae UCG.014, Tannerella and Campylobacter were significantly more abundant in autistic compared to non-autistic children. Furthermore, the former four bacteria that were significantly more abundant in the autistic children showed significant associations with parent-reported social difficulties, repetitive and restrictive behavior and with parent-reported anxiety-like behavior. Importantly, associations among oral microbiome and quantitative diagnostic characteristics were not significantly driven by differences in lifestyle variables. This exploratory study reveals significant differences in oral microbiome composition between autistic and non-autistic children, even while controlling for potential confounding lifestyle variables. Furthermore, the significant associations with clinical characteristics suggest that individual differences in microbiome composition might be involved in shaping the clinical phenotype of autism. However, these associations warrant further exploration of the oral microbiome's potential beyond the oral cavity and specifically with respect to neuropsychiatric conditions.