The Role of Altered Bacterial Gut Microbiota and Gut Mycobiota on Gastrointestinal Symptoms Associated with Autism Spectrum Disorder (ASD).

John Hiett

Introduction. Autism spectrum disorder (ASD) is a developmental disability that includes social and communication impairments, restricted interests, and repetitive behaviors. Although the etiology of ASD in not completely known, a very strong genetic component has been identified.5 Compared to healthy controls, children and adults with ASD typically suffer from a wide variety of gastrointestinal symptoms associated with the disorder. These include, but are not limited to, constipation and inflammatory bowel disease (IBD).1,2,3,4 Recently, much research has been done in the testing and culturing of fecal waste in patients with ASD in order to paint an accurate picture of what the microbiome and mycobiome look like in those patients with ASD. This research points to altered levels of Clostridium, Firmicutes, Bacteroidetes, and Candida species in children with the disorder.3,4 Methods. Samples were collected from 40 young subjects with a previous diagnosis of ASD. The samples were pyrosequenced using the FastDNATM SPIN Kit for Feces, and the gut microbiota and mycobiota were compared to the biomes of age and sex-matched neurotypical healthy subjects.3 Results. When compared to the microbiome and mycobiome of neurotypical subjects, children and adults with ASD show reduced diversity. Most notably, at phylum level analysis subjects showed a higher Firmicudetes/Bacteroidetes ratio3 due to a significant decrease in the number of Bacteroidetes species. Furthermore, in another very similar study focused on Clostridium species4, researchers noted enhanced levels of C. Perfringens in the gut of children with ASD, as well as statistically significant increases in the amount of beta2-toxin-gene. In addition to changes in gut bacteria, researches who discovered a higher Firmicudetes/Bacteroidetes ratio in children with ASD also noted enhanced levels of the fungus Candida.3 Conclusions. Studies have demonstrated that children and adults with ASD harbor statistically significant changes in their gut microbiome and mycobiome, including decreased Bacteroidetes species, and increased levels of C. Perfringens and Candida species. Although it is not believed that repairing the biome of ASD afflicted individuals to resemble that of neurotypical subjects will alleviate the behavioral or social symptoms of the disorder, it is believed that achieving normality in the gut will alleviate many of the gastrointestinal symptoms associated with ASD. Relieving the symptoms of constipation and inflammatory bowel disease (IBD) may prove to be the first step in finding a cure for Austism Spectrum Disorder.2

  1. Lim JS, Lim MY, Choi Y, Ko GP. Modeling environmental risk factors of autism in mice induces IBD-related gut microbial dysbiosis and hyperserotonemia. Molecular Brain. April 2017.10(1):14.
  2. Luna RA, Oezguen N, Balderas M, et al. Distinct Microbiome-Neuroimmune Signatures Correlate With Functional Abdominal Pain in Children With Autism Spectrum Disorder. Cellular and Molecular Gastroenterology and Hepatology. March 2017. 219(1):229.
  3. Strati F, Cavalieri D, Albanese D, et al. New evidences on the altered gut microbiota in autism spectrum disorders. Microbiome. February 2017. 5(1):24.
  4. Finegold SM, Summanen PH, Downes J, Corbett K, Komoriya T. Detection of Clostridium perfringens toxin genes in the gut microbiota of autistic children. Anaerobe. February 2017.1(1):5.
  5. Christensen DL, Baio J, Braun KV, et al. Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, MMWR Surveill Summ, April 2016; 65(3):1-23
  6. Fakhoury, Marc, Imaging genetics in autism spectrum disorders: Linking genetics and brain imaging in the pursuit of the underlying neurobiological mechanisms, Progress in Neuro-Psychopharmacology and Biological Psychiatry, Available online 16 March 2017
  7. Gill SR, Pop M, DeBoy RT, et al. Metagenomic Analysis of the Human Distal Gut MicrobiomeScience (New York, NY). 2006;312(1):5778
  8. Caroline G.M. de Theije, Harm Wopereis, et al. Altered gut microbiota and activity in a murine model of autism spectrum disorders, Brain, Behavior, and Immunity, 37(1):197-20
  9. Johnson, Chris, et al. Identification and Evaluation of Children With Autism Spectrum Disorders, Pediatrics 2007;120(1):1183