Can oral microbiome dysbiosis affect the behavior of children with Autism Spectrum Disorders (ASD)? : Narrative review

Abstract

Background: Autism spectrum disorders (ASD) are complex developmental disorders characterised by several levels of social interaction and communication difficulties. The prevalence of children with ASD worldwide is around 1:160, and the number of cases of autism has increased significantly. The oral microbiome is a diverse microbial biofilm with the second most complex microbiota in the human body after the gut. Several factors, such as lifestyle and health, can influence the oral microbiome’s composition and metabolism. Children with ASD generally have poorer oral hygiene and suffer from periodontal disease and dental caries more than typical children; this is associated with behavioural disturbances, such as communication limitations, motoric limitations, eating habits and the side effects of drugs. Continued oral microbiome dysbiosis can lead to gut microbiome dysbiosis. There are two hypotheses for the transmission of oral bacteria to the gut, via the hematogenous route or via the enteral route. Gut microbiome dysbiosis may regulate social behaviour, such as emotional dissonance and anxiety, through blood-brain-barrier and gut-brain-axis pathways. When there is inflammation of the periodontal tissue in ASD children, it can cause lipopolysaccharide (LPS) leakage to the blood-brain barrier (BBB) that can cause an inflammatory response and disrupt metabolic activity in the central nervous system. Oral dysbiosis, which continues into gut dysbiosis, can affect behaviour through the gut-brain axis. This review aims to determine the impact of oral microbiome dysbiosis on the behaviour of children with ASD.