TABLE 2.

Altered gut microbiota composition in ASD patients (↑ = increased, ↓ = decreased).

Study subjects	Findings	References
13 autistic children and 8 control children	Clostridium↑ and Ruminococcus spp.↑	Finegold et al. (2002)
15 autistic children and 8 control children	C. bolteae↑, Clostridium clusters I↑, and Clostridium clusters XI↑	Song et al. (2004)
58 autistic children, 12 healthy siblings, and 10 control children	Clostridium clusters I↑ and Clostridium clusters II↑	Parracho et al. (2005)
33 autistic subjects,7 sibling controls, and 8 non-sibling control subjects	Bacteroidetes↑, Proteobacteria↑, Alkaliflexus↑, Desulfovibrio↑, Acetanaerobacterium↑, Bacteroides↑, Parabacteroides↑, Desulfovibrio spp. ↑, Bacteroides vulgatus↑, Actinobacteira↓, Turicibacter Clostridium↓, Firmicutes↓, Weissella↓, Helcococcus↓, Alkaliphilus↓ Anaerofilum↓, Pseudoramibacter↓, Ruminococcus↓, Streptococcus↓, Anaerovorax↓, Dialister↓, Lactococcus↓, Leuconostoc↓, and Ethanoligenens↓	Finegold et al. (2010)
15AUT-GI and 7 control-GI children	Betaproteobacteria↑, Bacteroidetes↓, and the ratio of Firmicutes/Bacteroidetes↑	Williams et al. (2011)
10 autistic children, 9 siblings, and 10 healthy children	Lactobacillus spp.↑, Desulfovibrio spp.↑, and Bacteroidetes/Firmicutes↓	Tomova et al. (2015)
35 children with ASD and 6 TD children	Sutterella↑, Odoribacter↑, Butyricimonas↑, Veillonella↓, Streptococcus↓, and Bacteroidetes/Firmicutes↑	Zhang et al. (2018)
48 children with ASD and 48 healthy children	Firmicutes↓, Proteobacteria↓, Verrucomicrobia↓, Bacteroidetes/Firmicutes↑, Dialister↓, Prevotella↑, Bacteroides↑, Megamonas↑, Escherichia/Shigella↓, Lachnospiracea_incertae_sedis↑, Clostridium XlVa↓, Eisenbergiella↓, Clostridium IV↓, Flavonifractor↓, Haemophilus↓, and Akkermansia↓	Zou et al. (2020)
77 children with ASD and 50 age-matched healthy children	Unidentified Lachnospiraceae↑, Clostridiales↑, Dorea↑, Erysipelotrichaceae↑, Collinsella↑, Lachnoclostridium↑, Bacteroides↓, Faecalibacterium↓, Parasutterella↓, and Paraprevotella↓	Ding et al. (2020)
9 autistic children, and 6 healthy children	Bacteroidales ↓, Selenomonadales↓, Prevotellaceae↓, and Ruminococcaceae↑	Sun et al. (2019)
143 ASD children, 143 age- and sex-matched TD individuals	Firmicutes↑, Firmicutes/Bacteroidetes↑, Megamonas↓, Proteobacteria↑, Actinobacteria↑, Bacteroidetes↓, Dialister↑, Escherichia-Shigella↑, Bifidobacterium↑, Prevotella 9↓, and Ruminococcus 2↓	Dan et al. (2020)
72 ASD and 74 TD children	Clostridium↑, Dialister↑, Coprobacillus↑, and Faecalibacterium↓	Wan et al. (2021)
11 ASD and 14 healthy control children	Actinobacteria↓, Bacteroidetes↑, Proteobacteria↑, Bacteroidetes/Firmicutes↑, Actinomycetaceae↓, Coriobacteriaceae↓, Oscillospira↑, Gemellaceae ↓, Streptococcaceae↓, Faecalibacterium prausnitzii↑, and Bifidobacteriaceae↓	Coretti et al. (2018)