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Title: Investigation of the gastrointestinal microbiota associated with autism spectrum disorders in children
Author: Ambrose, Holly N.
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Interest in the role of the gastrointestinal (GI) microbiota on host health has exponentially increased in recent years, with the microbiome now considered a major organ that can have systematic effects. This has included hypotheses and subsequent studies of possible roles of the GI micro biota in autistic spectrum disorders (ASD). Previous data demonstrated differences in the faecal microbiota of ASD and non-ASD children, particularly within the Clostridium populations (most notably Clostridium clusters I and II). The primary objective of this work was to investigate the diversity and dynamics of the anaerobic faecal spore-forming bacteria (including Clostridium) associated with ASD using a range of enrichment methods. Twenty-two faecal samples were collected from 11 subjects (5 ASD, 3 non-ASD siblings and 3 unrelated non-ASD children), yielding 2340 isolates - 1286 'biotypes' comprising 109 species (60 of which were non spore-formers) from anaerobic cultivation across 8 enrichment methods (aerobic dessication, anaerobic dessication, heat and ethanol treatments of faecal samples, each cultured on Fastidious anaerobe agar and Reinforced clostridial agar). All enrichment methods contributed to the anerobic sporeformer diversity, with temporal stability for some biotypes demonstrated whilst others fluctuated from sample to sample. Biotype specificity was also found among commonly isolated anaerobic spore-formers for the ability to utilize tryptophan and/or phenylalanine. Multiple antibiotic resistance was also common, with more than 50 % of common Clostridium biotypes showing resistance to vancomycin (both ASD and non-ASD isolates). Aerobic cultivation of 7 of the faecal samples (4 ASD and 1 non-ASD subjects; all four treatments) on Tryptone soya agar isolated 180 'biotypes' (446 isolates) including 62 spore-former species (46 Bocillioceoce species, 12 Paenibacillaceae species, 3 Clostridium species and Rummeliibacillus pycnus). Whilst heat treatment gave the greatest diversity of Bacillus, all treatments again contributed to the overall diversity recovered. This is the first study of aerobic spore-formers harboured by ASD children. The diversity of anaerobic and aerobic spore-formers described herein extends our knowledge of these populations within the GI microbiota of ASD and non-ASD children, and demonstrated that employment of multiple enrichment methods is required to maximise the recovery of sporeformer diversity within such complex microbial ecosystems. The Clostridium data corroborates previously published findings regarding distinctions in the Clostridium populations of ASD and non-ASD cohorts (particularly Clostridium clusters I and II). The extensive collection of Clostridium biotypes obtained from the anaerobic spore-former work is an invaluable resource that could be applied to develop and/or validate molecular-based techniques for future studies examining the diversity, dynamics and relative abundance of Clostridium populations at subspecies levels. The resource could also be used for phenotypic and/or functional studies (including metabolomics) of faecal bacteria. Design and method development of a statistically powered feeding study investigating the effects of L. plantarum WCFSI on GI symptoms and faecal microbiota in ASD
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available