Bimodal distribution of intestinal Candida in children with autism and its potential link with worse ASD symptoms

Abstract

The gastrointestinal (GI) tract harbors a complex and remarkably diverse microbial ecosystem that profoundly impacts various aspects of health and pathophysiology. While bacteria overwhelmingly represent most of the GI microbiota, it is imperative to consider the presence and function of fungal constituents (i.e. mycobiota) within the GI ecosystem. The substantial incidence of GI disorders and associated manifestations in children diagnosed with autism spectrum disorder (ASD) suggests a plausible contributory role of the gut mycobiota. This work aimed to elucidate the gut mycobiota in a cohort of 38 typically developing children (TD) and 40 children with ASD. Fecal samples were collected from all participants, autism severity and GI symptoms were assessed to unravel the potential implications of mycobiota alterations in the gut. We performed fungal internal transcribed spacer (ITS) gene amplicon sequencing to analyze the fungal composition and investigate their relationship with GI and autism symptoms. Among gut mycobiota, Saccharomyces cerevisiae was significantly lower (relative abundance) in the ASD fecal samples compared to TD children. Candida and C. albicans demonstrated a bimodal distribution among children with ASD. The small subset of children with elevated C. albicans or decreased S. cerevisiae had increased Autism Treatment Evaluation Checklist (ATEC) scores. Our findings suggest that a deficit of S. cerevisiae, and an overgrowth of C. albicans in a subset of children is associated with worse autism severity. Future work employing shotgun metagenomics with a larger cohort is encouraged to advance understanding of the functional role of fungi, and their possible interplay with GI symptoms and autism severity in children with ASD.

Keywords

• Autism spectrum disorder (ASD)
• internal transcribed spacer (ITS) sequencing
• mycobiota
• fungal microbiota
• candida albicans