TABLE 1.

Gastrointestinal microbiome analysis studies in functional dyspepsia.

Ref	Species	Number (FD/controls, n)	Technique for microbiota identification	Principal findings
Qiu et al. (2017)	Rats	3/3	16S rDNA V4 gene sequencing	Lower abundance of the bacteroidetes phylum, higher abundance of the proteobacteria and firmicutes phylum
Zhang et al. (2020)	Mice	12/12	16S rRNA gene sequencing	Down regulation of bacteroidetes, Lactobacillus, and prevotellaceae, up regulation of proteobacteria, verrucomicrobia, epsilonbacteraeota, firmicutes, lachnospiraceae NK4A136 group, and lachnospiraceae
Zhong et al. (2017)	humans	9/9	16S rRNA gene sequencing	Lower abundance of actinomycete, atopobium collin, leptotrichia trevisan, prevotella, and veillonella, The total relative abundance of bacteria was positively correlated with the severity of clinical symptoms
Fukui et al. (2020)	humans	11/7	16S rRNA V3-V4 gene sequencing	Up regulation of the phylum Firmicutes and Streptococcus, The relative abundance of Streptococcus was positively correlated with upper gastrointestinal symptoms
Nakae et al. (2016)	humans	44/44	16S rDNA gene sequencing	Lower abundance of Prevotella, higher abundance of Bifidobacterium and Clostridium, The relative abundance of Prevotella was negatively correlated with the severity of PDS symptoms