Gut Microbial Dysbiosis in Indian Children with Autism Spectrum Disorders Original paper

What was studied?

This study investigated gut microbial dysbiosis in Indian children with autism, using 16S rRNA gene sequencing to compare fecal microbiota from 30 children with autism spectrum disorder (ASD) and 24 age- and family-matched healthy controls. By examining patterns of microbial abundance, diversity, and taxonomic shifts, the researchers aimed to identify microbial signatures linked to autism within an Indian dietary and cultural context. Because participants consumed similar omnivorous native diets and had no recent exposure to antibiotics or gluten-free regimens, the study provided a controlled view of microbiome differences independent of major dietary disruptions. A comparative meta-analysis incorporating a U.S. ASD cohort further tested whether shared microbial markers persist across geography and diet.

Who was studied?

Participants included 30 Indian children diagnosed with ASD using CARS, DSM-5–aligned INDT-ASD, and the Indian ISAA scale. All had severe ASD and frequently reported gastrointestinal symptoms such as constipation, diarrhea, and maldigestion. The control group consisted of 24 matched healthy siblings or close relatives without GI symptoms or ASD. Children were between 3 and 16 years of age, with ASD cases showing significantly lower BMI and a strong male predominance. All participants consumed similar native diets, avoiding confounding influences of gluten-free or casein-free diets common in many ASD cohorts.

Most important findings

The study found that α-diversity and overall species richness did not differ significantly between ASD and healthy children. However, taxonomic composition varied strongly. ASD children showed increased abundances of Lactobacillaceae, Bifidobacteriaceae, and Veillonellaceae, while healthy children were dominated by Prevotellaceae—a hallmark of Indian microbiomes tied to carbohydrate-rich diets. Lactobacillus, especially L. ruminis, was strikingly elevated, with a ~32-fold higher abundance in ASD children. Megasphaera and Mitsuokella, both SCFA-linked taxa, were also enriched. In contrast, SCFA-producing genera such as Faecalibacterium and Roseburia were depleted, suggesting weakened butyrate-associated metabolic pathways. Meta-analysis with the U.S. dataset confirmed Lactobacillus as the only genus consistently elevated in ASD across populations, despite major dietary differences. This consistency positions Lactobacillus as a potential cross-population microbial marker of ASD.

Key implications

The findings reinforce the concept that autism is associated with gut microbial dysbiosis, but highlight population-specific patterns shaped by diet and geography. The consistent overrepresentation of Lactobacillus across Indian and U.S. cohorts suggests a robust microbial correlate of ASD, though causality remains unclear. Reduced SCFA-producing bacteria may contribute to impaired gut barrier integrity and altered neuroimmune signaling through the gut–brain axis. The study broadens global microbiome–ASD research by providing the largest ASD microbiome dataset from India and emphasizing the need for functional studies integrating metagenomics and metabolomics to clarify mechanistic links and therapeutic potential.

Citation

Pulikkan J, Maji A, Dhakan DB, et al. Gut microbial dysbiosis in Indian children with autism spectrum disorders. Microbial Ecology. 2018. doi:10.1007/s00248-018-1176-2