167 The Microbiome Signature of Autistic Children Is Characterized by Decreased Diversity and Dysbiosis

Abstract

Background: Autism Spectrum Disorders (ASDs) are complex neuro-developmental disorders characterized by cognitive defects, social interaction skills impairments and communication, language and behavioral problems. A strong correlation between autism severity and GI symptoms, alterations of intestinal permeability (IP), presence of inflammation and intestinal dysbiosis has been described. It has recently been proposed that alterations of the intestinal microbiota could contribute to the development of ASDs. Recent studies demonstrated that autistic children with gastrointestinal symptoms show major fecal microbiota alterations. In this study we aimed to study the fecal candida and bacterial microbiota, their correlation to intestinal permeability, in autistic children compared to normal developing children, in order to provide rational basis to a possible specific therapeutic intervention in restoring gut microflora in ASDs. Material and Methods: We collected stool samples from 47 subjects with ASDs (40 boys and 7 girls, mean age 6.0 ± 2.8 yr), and 33 healthy children matched controls (24 boys and 9 girls, mean age 7.3 ± 3.1 yr). Search for Candida culture and biochemical identification of the colonies were performed by Sabouraud Dextrose Agar + Chloramphenicol + Gentamicin, Oxoid Products Microbiology and analized by ID 32 C (bioMerieux) system. In a subgroup of 12 ASDs subjects (8 boys and 4 girls, mean age 6.8 ± 2.9 ), and 16 healthy children matched controls (8 boys and 8 girls, mean age 7.3 ± 3.1 yr), total microbial DNA was extracted and 16S variable region V4 amplified by PCR. The results were analyzed by QIIME software. Intestinal Permeability (IP) was assessed with the lactulose/mannitol (LA/MA) test. Results: Compared to HC, ASDs samples presented an increased number of Proteobacteria combined with a reduction of Bacteroidetes and Actinobacteria. Microbial diversity was reduced in ASDs children, albeit they were more phylogenetically different. Interestingly, β-diversity analysis showed 2 distinct clouds in ASDs children, one dominated by E. Coli and the other with no clear domination. Candida spp was detected in the stools of 15 ASD children (31.9%) compared to controls (6.1%). Interestingly in ASDs, C. albicans was most frequently identified (9 out of 15 cases). Finally, IP resulted altered in 42.4% of ASDs compared to 22.7% of controls (p < 0.05). No correlation was detected between altered IP and either microbiome composition or candidosis. Conclusions: In this proof-of-concept study we establish that ASD children have a specific microbiome signature characterized by decreased diversity and quantitative representation of some specific phyla. Candida infestation, particularly C. albicans was more frequently detected in ASD children than controls.