Human epidemiologic studies linking gut microbiota changes to ASD symptomology

PublicationCohort PopulationType of Analysis and/or TreatmentMajor Finding
Gondalia et al. (2012)ASD children without GI dysfunction (n = 23); ASD children with GI dysfunction (n = 28); neurotypical siblings (n = 53)• bEFAP was performed on the stool samples from all three groups.• Firmicutes (70%), Bacteroidetes (20%), and Proteobacterias (4%) comprised the major microbiota present in the stool regardless of disease state and sociodemographic features.
• No evidence was found linking gut disease, dysbiosis, and ASD symptoms.
Song et al. (2004)ASD children (n = 15); nonrelated controls (n = 8)• Group and species-specific primers were designed to target the 16S rRNA genes for qRT-PCR analysis on the stool samples.C. bolteae and clusters I and XI were elevated in the stool of ASD children.
Finegold et al. (2002)ASD children (n = 13); nonrelated controls (n = 8)• Bacterial cultures were performed on the stool samples.• Nine species of Clostridium were present in ASD but not the control children, where three unique species were identified.
• Non-spore-forming anaerobes and microaerophilic bacteria were abudant in ASD but lacking in the control children.
Parracho et al. 2005)ASD children (n = 58); control siblings (n = 12); nonrelated controls (n = 10)• FISH analysis was performed on the stool samples.C. histolyticum (Clostrium clusters I and II) was abundant in ASD children.
• Nonautistic siblings possess intermediate levels of this intestinal microbe.
Finegold et al. (2010)ASD children (n = 33); control siblings (n = 7); nonrelated controls (n = 8)• bEFAP procedure was used to analyze the stool samples.• Phyla changes: Bacteroidetes and Protebacteria were increased in ASD children; whereas Firmcutes and Actinobacteria were less abundant in the stool of this group.
• Genus changes: Delsufovibrio, Bacteroides, Alkaliflexus, Acetanaerobacterium, and Parabacteroides were elevated in ASD children, whereas Clostridum, Weissella, Turicibacter, Anaerofilum, Pseudoramibacter, Ruminococcus, and Streptococcus were decreased in this group.
Tomova et al. (2015)ASD children (n = 10); control siblings (n = 9); nonrelated controls (n = 10)• qRT-PCR analysis was performed on the stool samples.• ASD children showed significant reduction in the Bacteroidetes/Firmcutes ratio but increased amount of Lactobacillus spp.
• Probiotic supplementation of one Children Dophilus capsule, which contains three strains of Lactobacillus (60%), two strains of Bifidumbacteria (25%), and one strain of Streptococcus (15%) was provided orally to the ASD group 3 times a day for 4 months.Delsulfovibrio spp. showed a trend to be increased in this group, especially with increasing autistic severity.
• Clinical severity of GI symptoms was positively correlated with autism severity.
• Probiotic supplementation of the autistic children corrected the imbalanced Bacteroidetes/Firmicutes ratio, suppressed Delsufovibrio spp., and increased the amount of Bifidobacterium spp. present in the stool.
Williams et al. (2011)ASD children with GI dysfunction (n = 15); nonrelated controls with GI symptoms only (n = 7)• qRT-PCR with human mRNA samples for SI, MGAM, LCT, SGLT1, GLUT2, Vilin, and CDX2.• ASD children exhibited decreased expression of disaccharidases, hexose transporters, and the transcription factor CDX2.
• Pyrosequencing of intestinal microbiota.• The host transcriptomic changes correlated with the degree of gut dysbiosis observed in this ASD child cohort.
• qRT-PCR of Bacteroidete and Firmicute 16s rRNA genes from intestinal biopsies.• ASD children showed decrease amounts of Bacteroidetes and ratio of Bacteroidetes to Firmcutes, and greater preponderance of Betaproteobacteria in the intestinal biopsy samples.
Wang et al. (2013)ASD children (n = 23); control siblings (n = 22); nonrelated controls (n = 9)• qPCR on the stool samples.• ASD children with and without GI disorders showed high amounts of fecal Sutterella spp.
Ruminococcus torques was elevated in the stool of children with ASD and GI symptoms compared with those without any such disorders.
De Angelis et al. (2013)ASD children (n = 10); nonrelated controls (n = 10)• bEFAP procedure was used to analyze the stool samples.• Phylum changes were evident in Bacteroidetes, Firmicutes, Fusbobacteria, and Verrucomicrobia in ASD compared with health children.
• Measurement of free amino acid and volatile organic compounds in the stool samples.• Caloramator, Sarcina, and Clostridium genera were greater in ASD children.
• Variations within the Lachnospracease family were observed.
• ASD children possessed greater amounts of fecal Bacteroidetes genera, select Alistipes and Akkermansia species, but Sutterellaceae, Enterobacteriaceae, Eubacteriaceae and Bifidobacterium species were reduced in this group.
• Levels of free amino acids and volatile organic compounds within the stool were affected in this group.
Wang et al. (2011)ASD children (n = 23); control siblings (n = 22); nonrelated controls (n = 9)• qPCR on the stool samples.• Bifidobacteria species was reduced and mucolytic bacterium, Akkermansia muciniphilia, was increased in the stool of ASD children.
Williams et al. (2012)ASD children with GI dysfunction (n = 15); nonrelated controls with GI symptoms only (n = 7)• Pyrosequencing and qPCR of ileal and cecal biopsies.Sutterella spp. (wadsworthensis and stercoicanis) predominated in the gut microbiota of ASD children with concurrent GI dysfunction, but these species were absent in children with GI symptoms only.
Kang et al. (2013)ASD children (n = 20); nonrelated controls (n = 20)• Pyrosequencing of the stool samples.• The presence of ASD rather than GI symptoms was a better predictor of a less diverse gut microbiota composition.
• The genera Prevotella, Coprococcus, and unclassified Veillonellaceae were reduced in the stool of ASD children.
Adams et al. (2011)ASD children (not on probiotic supplement and those taking a daily probiotic, n = 58); nonrelated controls (n = 39)• Bacterial culture of the stool samples.• There was a positive correlation with GI symptoms and ASD clinical severity.
• Concentrations of Lysozyme, lactoferrin, secretory IgA, elastase, SCFAs were measured in the stool.• Decreased number of SCFAs, specifically acetate, propionate, and valerate were identified in ASD children, especially those consuming a daily probiotic.
• The stool of ASD children contained less Bifidobacter but greater amounts of Lactobacillus.
• Lysozyme was suppressed in ASD children.
Sandler et al. (2000)Regressive-onset autistic children (n = 11)• The children received a 12-week treatment of oral vancomycin (125 mg 4 times a day for a daily dose of 500 mg).• The vancomycin treatment improved the behavioral scores of ASD children, but the beneficial effects were transient with the behavioral symptoms recurring upon discontinuation of the antibiotic.
• Once antibiotic treatment was discontinued, the children received probiotic supplementation with a mixture of L. acidophilus, L. bulgaricus, and B. bifidum (40 × 109 CFU/ml).
• Psychologic evaluations were performed before and after the antibiotic treatment.
Wang et al. (2012)ASD children (n = 23); nonrelated controls (n = 31)• Concentrations of SCFAs, phenols, and ammonia were measured in the stool samples.• Fecal SCFAs were significantly higher in ASD children.
• Acetic, butyric, isobutryic, valeric, and isovaleric acids were elevated in the stool of ASD children, whereas caproic acid was reduced.
• The ASD group had greater ammonia concentration in the stool.
Yap et al. (2010)ASD children (n = 39 with 35 males and 4 females); control siblings (n = 28 with 14 males and 14 females); nonrelated controls (n = 34 with 17 males and 17 females)• H NMR spectroscopy and pattern recognition methods were used to measure the concentration of free amino acids and bacterial metabolites in the urine.• The free amino acids glutamate and taurine were elevated in the urine of ASD children.
• Disturbances in the patterns of bacterial metabolites dimethylamine, hippurate, and phenylacetylglutamine were also observed in this group.
Kalużna-Czaplńnska and Blaszczyk (2012)ASD children with GI dysfunction (n = 22)• Concentrations of DA, LA, and the ratio of DA/LA in the urine were determined by capillary gas chromatography/mass spectrometry before and after probiotic therapy.• The concentration of DA in the urine was higher in ASD children compared with controls before and after probiotic supplementation.
• The children were provided an oral probiotic capsule containing L. acidophilus twice daily for 2 months (strain Rosell-11, containing 5 × 109 CFU/gram).• The probiotic therapy appeared to partially improve the elevated urinary concentrations of DA and ratio of DA/LA, and there was noticeable improvement in the behaviors of ASD children, particularly in concentration ability and carrying out orders.
  • bEFAP, bacterial tag encoded FLX amplicon pyrosequencing; CFU, colony forming unit; FISH, fluorescent in situ hybridization; LA, L-arabinitol; qRT-PCR, quantitative real-time polymerase chain reaction.