Table 1.

Recent findings on changes in the SpA gut microbiota.

	Study Subjects	Key findings	Ecological changes in the flora	Strains with increased abundance		Strains with reduced abundance
1	Microbial profiles for terminal ileum biopsy specimens obtained from patients with recent-onset tumor necrosis factor antagonist-naive AS (Costello et al., 2015)	Microbial communities in AS differ significantly from those in healthy control subjects, driven by a higher abundance of 5 families of bacteria	The microbial composition was demonstrated to correlate with disease status	Lachnospiraceae, Ruminococcaceae, Rikenellaceae, Porphyromonadaceae, Bacteroidaceae		Veillonellaceae, Prevotellaceae
2	Stool specimens from 150 AS patients (Klingberg et al., 2019)	There is a distinct fecal microbiota profile, which is associated with the fecal calprotectin levels.	87% of patients with ecological disorders	Proteobacteria, Enterobacteriaceae, Bacilli, Streptococcus spp., Actinobacteria		Bacteroides, Lachnospiraceae
3	Chinese AS patient cohort (Wen et al., 2017)	Reduced abundance of melanin-producing Prevotella, Prevotella spp. and Anaphyllobacter spp.	Ecological disorders			Bacillus spp., Prevotella, melanogaster, Prevotella spp.
4	Stool samples from 22 patients with AS (Li et al., 2019)	Increased abundance of Bacillus variegatus and reduced Bacillus mimicus	Lower biodiversity ratios; significant reduction in the diversity of intestinal fungi	Ascomycota, Cysticercus		Basidiomycota, Stretchers
5	Stool samples from two AS cohorts (Breban et al., 2017)	Ruminal cocci may be a potential marker of disease activity	A unique ecological disorder	align="left"> Rumenococcus
6	27 patients with SpA (Tito et al., 2017)	Dialister may be a potential microbial marker of disease activity	Significant differences in the microbiological composition of the gut in patients with microscopic intestinal inflammation	Dialister
7	Macrogenome sequencing of stool samples from patients with IBD (Hall et al., 2017)	Significant increase in the abundance of parthenogenic anaerobic bacteria tolerant to oxidative stress; dramatic but transient rumen cocci blooms coinciding with increased disease activity	Low diversity	Rumenococcus, Parthenogenic anaerobic bacteria
8	A total of 174 mucus samples from 43 UC and 26 CD patients (Nishino et al., 2018)	Significant increase in the Metaplasma phylum and significant decrease in the phylum Firmicutes and Bacteroidetes; CD and UC have different microbial community structures associated with mucous membranes.	Significant reduction in alpha diversity	Phylum Metaplasma		Phylum Firmicutes, Bacteroidetes
9	Stool analysis of patients with IBD (Alam et al., 2020)	The changed bacterial groups are those that do not co-exist well with the common intestinal commensal bacteria	Low microbiome diversity	Coriobacteriaceae, Prevotellaceae, Burkholderiaceae, Veillonellaceae, Streptococcaceae, Pseudomonadaceae, Acidaminococcaceae
10	Recent-onset, DMARD-naive PsA (Scher et al., 2015)	Low relative abundance of Akkermansia and Ruminoccocus hb as a characteristic of the PsA gut microbiota	Reduced diversity of the gut microbiota due to the low relative abundance of several taxa.			Akkermansia, Ruminoccocus
11	52 psoriasis patients (Codoner et al., 2018)	Type 2 patients have a higher frequency of bacterial translocation and more frequent inflammatory states		Faecalibacterium		Bacteriodes