Recent data supports the hypothesis that the alteration of the microbiota plays a pivotal role in the pathogenesis of autism spectrum disorder (ASD). Several studies show that the gut microbiota of ASD individuals may be in part responsible for a deregulation of the gut-brain axis with particular relation to the onset of internalizing and externalizing symptoms. Besides, children with ASD are frequently characterized by gastrointestinal (GI) symptoms which may be linked to gut dysbiosis. Noteworthy, animal studies suggest that Lactobacillus (L.) reuteri PTA-6475 selectively rescues social deficits in genetic and idiopathic ASD models.

Objectives:

Aim of this study is to assess the effect of a 6 month L.Reuteri (DSM17938 and ATCC PTA6475) supplementation on GI symptoms and gut microbiota in a sample of ASD children

Methods:

We performed a randomized double-blind placebo-controlled trial on forty-three children with ASD (35 males 8 females; age range 3-8 years). Participants were randomized to L. Reuteri (DSM17938 and ATCC PTA6475) supplementation or placebo for a total of 180 days. At baseline (T0), after three months (T1) and at six months (T2), all participants underwent a standardized clinical assessment of GI problems (Gastrointestinal Symptoms Rating Scale), autism core symptoms and social behavior (Autism Diagnostic Observation Schedule-2^nd; Social Responsiveness Scale; Adaptive Behavior Assessment 2^nd ). Gut microbiota analysis was performed at all timepoints by DNA extraction and then sequenced with MGI DNBT7.

Results:

Preliminary results on gut microbiota analysis show that, at baseline, ASD children are characterized by a significant increase of Bacteriodetes (p<0,05) and a decrease of Actinobacteria (p<0,034) and Lactobacillus abundance (p<0.01). After probiotic supplementation, we found that children receiving probiotic supplementation – in comparison to the placebo group - have a significant increase of: a) abundance of Bacteriodetes (p<0.006), b) abundance of Intestinomonas butyciroproducens family (p=0.02). L. Reuteri was shown to change the microbiota composition of children treated with probiotic, leading to an increase in biodiversity as assessed by the Shannon Index.

Conclusions:

The present clinical trial provides new insights into the gut-brain connection in ASD and shows that the supplementation with L. Reuteri (DSM17938 and ATCC PTA6475) fosters the abundance of anti-inflammatory species able to produce short chain fatty acids, increases microbiota diversity and improves GI symptoms. Further gut microbiota analysis that considers the social behavioral outcome after probiotic supplementation with L.Reuteri, may give a better understanding of the role played by microbiota in ASD.