Caries influences the composition of oral microorganisms in male children with ASD

Background: Autism Spectrum Disorders (ASD) is a prevalent neurodevelopmental disorder, with growing evidence suggesting that certain oral microorganisms may worsen ASD symptoms. Caries is closely linked to the nervous system and influences the composition of oral microorganisms. Therefore, when studying the oral microbial composition in ASD, the effects of caries must be excluded to accurately identify potential oral causative agents of ASD. Methods: A case-control study was conducted with 30 children diagnosed with ASD and 34 typically developing (TD) control children, both with and without caries, from Guangzhou city. Participants were categorized into four groups: ASD without caries (ASD-N), ASD with caries (ASD-C), TD without caries (TD-N), and TD with caries (TD-C). Plaque and saliva samples were collected from all participants and analyzed using 16S rRNA high-throughput sequencing to evaluate changes in oral microbial composition and diversity in children with ASD under varying caries conditions. Results: The alpha diversity of plaque and saliva microorganisms was generally lower, and beta diversity differed significantly between children with ASD and control groups. At the phylum level, the two most dominant phyla were Bacillota and Actinomycetota. At the genus level, the predominant genera were Streptococcus and Porphyromonas. LEfSe analysis revealed that certain taxa, such as Ruminococcaceae bacterium UCG-005 and Lactobacillus mucilaginosus in dental plaque, and Actinobacillus in saliva, were significantly more abundant in caries-free ASD children compared to caries-free controls(P < 0.001). Furthermore, Prevotella, Carnobacterium and Suttonella in plaque, along with Peptostreptococcus in saliva, were more prevalent in caries-free ASD children compared to caries-affected controls (P < 0.001). Conclusion: Caries impacts the diversity and composition of oral microorganisms in children with ASD. The dominant genera, Streptococcus and Porphyromonas, are linked to both caries and the development of ASD. Certain biomarkers in children with caries were associated with caries, whereas others in caries-free ASD children were linked to ASD itself. These findings offer new insights into identifying the true oral pathogens related to ASD.