Table 3.

Variations of gut microbiome in autism.

Disorder	Subjects	Test	Increased Levels	Decreased Levels	Study
ASD	143 ASD children, mean age 4.937 +/− 0.155 143 TD individuals, mean age 5.189 +/− 0.170	Fecal microbiota analysis	Firmicutes Proteobacteria Actinobacteria Dialister Escherichia-Shigella Bifidobacterium	Bacteroidetes	Dan et al., (2020) [56]
ASD	78 ASD children, mean age 4.96 +/− 1.01 58 HCs, mean age 4.90 +/− 0.97	Fecal microbiota analysis	Bacteroides Parabacteroides Sutterella Lachnospira Bacillus Bilophila Lactococcus Lachnobacterium Oscillospira	-	Zhai et al., (2019) [57]
ASD	48 children, age 2–7 48 HCs, age 4	Fecal microbiota analysis	At the phylum level, Bacteroidetes; at the genus level, Bacteroides Prevotella Lachnospiracea_incertae_sedis Megamonas	At the phylum level, Firmicutes Proteobacteria Verrucomicrobia; at the genus level, Clostridium XlVa Eisenbergiella Clostridium IV Flavonifractor Escherichia/Shigella Haemophilus Akkermansia Dialister	Zou et al., (2020) [58]
ASD	33 ASD children, age 2–13 7 non-autistic siblings 8 HCs	Fecal microbiota analysis	Desulfovibrio Bacteroidetes vulgatus	-	Finegold et al., (2010) [46]
ASD	41 ASD children, age 2–18 45 non-autistic siblings 45 HCs	Fecal microbiota analysis	Bacteroides Ruminococcus	-	Ahmed et al., (2020) [59]
ASD	77 ASD children, age 2–7 50 HCs	Fecal microbiota analysis	unidentified Lachnospiraceae Clostridiales Erysipelotrichaceae Dorea Collinsella Lachnoclostridium	Bacteroides Faecalibacterium Parasutterella Paraprevotella	Ding et al., (2020) [60]
ASD	20 ASD children and 20 HCs, age 3–16	Fecal microbiota analysis	Akkermansia	Prevotella Coprococcus Veillonellaceae	Kang et al., (2013) [61]
ASD	23 ASD children 22 non-ASD siblings 9 HCs	Fecal microbiota analysis	Sutterella Ruminococcus torques	-	Wang et al., (2013) [62]

ASD—autism spectrum disorder; HCs—healthy controls.