Microbial dial: How the gut microbiome tunes the severity of autism spectrum disorder

Table 1 Summary of altered gut microbiota in autism spectrum disorder patients

Microbial group	Observed change in ASD	Potential impact/significance
Bifidobacterium	Decreased	Loss of beneficial commensals; linked to reduced gut barrier support[17,19,22]
Prevotella	Decreased	Reduced diversity; often associated with plant-based fiber fermentation[17,22]
Firmicutes	Decreased	General reduction in diversity and beneficial metabolic output[19]
Clostridia/Clostridiales	Increased	Overgrowth of potentially pathogenic taxa; linked to toxin production[19,21]
Desulfovibrio	Increased	Associated with sulfur-reducing bacteria; can be inflammatory[17,19]
Enterobacteriaceae	Increased	Overrepresentation of opportunistic pathogens[19]
Overall diversity	Decreased	Reduced “resilience” of the gut ecosystem; linked to GI symptom severity[19,22]

This table summarizes the key microbial changes observed in individuals with autism spectrum disorder compared to neurotypical controls. ASD: Autism spectrum disorder; GI: Gastrointestinal.