Autism Spectrum Disorder (ASD) with and without Mental Regression is Associated with Changes in the Fecal Microbiota Original paper

What was studied?

This study examined ASD fecal microbiota changes by comparing fecal metagenomic profiles from children with autism spectrum disorder (ASD) to healthy controls, with an additional focus on whether mental regression—a clinically distinct ASD phenotype—influences gut microbial composition. Using next-generation sequencing of the 16S rRNA V3–V4 regions, the researchers quantified gut microbial abundances at phylum, class, family, genus, and species levels. The study integrated dietary data to explore microbiota–diet interactions, offering a comprehensive microbiome assessment.

Who was studied?

The study included 48 children with ASD (aged 2–6 years): 30 without mental regression (ANMR) and 18 with mental regression (AMR). A comparison group of 57 age- and sex-matched neurotypical children served as controls. All participants were recruited from Spanish pediatric clinical settings. The ASD diagnoses were rigorously confirmed using ICD-10 and DSM-5 criteria alongside established diagnostic tools such as ADOS and PDDBI. Children with medical comorbidities or medications that could influence microbiota were excluded. Dietary intake data were collected using validated questionnaires.

Most important findings

The study revealed distinct ASD fecal microbiota changes across multiple taxonomic levels. Children with ASD showed elevated Actinobacteria and Proteobacteria at the phylum level, with Actinobacteria, Bacilli, Erysipelotrichi, and Gammaproteobacteria increased at the class level. Proteobacteria elevation was specific to AMR children. Families enriched in ASD included Bacillaceae, Bifidobacteriaceae, Corynebacteriaceae, Enterobacteriaceae, Enterococcaceae, Erysipelotrichaceae, Fusobacteriaceae, Microbacteriaceae, and Thermoactinomycetaceae, while Lachnospiraceae was reduced. At the genus and species levels, ASD children exhibited higher abundances of Bacillus, Bifidobacterium, Butyrivibrio, Enterococcus, Hespellia, Prevotella, Clostridium bolteae, and Clostridium difficile. AMR children uniquely displayed higher Enterococcus and Thermoactinomycetaceae. PCA integrating diet and microbiota suggested distinct diet–microbiome correlations in ASD, with sweets, snacks, and processed meats clustering with specific microbial signatures.

Key implications

These findings support a biologically meaningful link between gut microbial composition and ASD phenotypes. The differentiation between AMR and ANMR subgroups demonstrates that ASD is not microbiologically homogeneous and that behavioral phenotypes may correspond to unique microbial signatures. Elevated Proteobacteria—a phylum often associated with inflammation—particularly in AMR children, suggests potential mechanistic pathways involving gut permeability or immune dysregulation. The enrichment of taxa such as Clostridium bolteae aligns with prior reports linking Clostridia to ASD-related gastrointestinal symptoms. The diet-microbiota interactions observed underscore the need to consider dietary habits when interpreting microbiome shifts in ASD. Overall, the findings highlight the importance of integrating metagenomics with nutritional and behavioral assessments to better understand ASD heterogeneity and inform future microbiome-targeted interventions.

Citation

Plaza-Díaz J, Gómez-Fernández A, Chueca N, et al. Autism Spectrum Disorder (ASD) with and without Mental Regression Is Associated with Changes in the Fecal Microbiota.Nutrients. 2019;11(2):337. doi:10.3390/nu11020337