Table 1.

Microorganisms altered in multiple sclerosis (MS).

Kingdom	Phylum	Class	Order	Family	Genus	Species	Abundance	Effects on the immune system	Reference
Bacteria	Proteobacteria	Alphaproteobacteria	Rhizobiales	Brucellaceae	Mycoplana		Increased in RRMS		(20)
				Hyphomicrobiaceae	Gemmiger		Increased in PPMS		(85)
		Betaproteobacteria	Burkholderiales	Sutterellaceae	Sutterella		Decreased in MS		(19)
		Gammaproteobacteria	Pseudomonadales	Pseudomonadaceae	Pseudomonas		Increased in RRMS		(20)
			Pasteurellales	Pasteurellales	Haemophilus		Decreased in MS		(20)
		Deltaproteobacteria	Desulfovibrionales	Desulfovibrionaceae			Increased in pediatric MS		(25)
	Bacteroidetes	Sphingobacteriia	Sphingobacteriales	Sphingobacteriaceae	Pedobacter		Increased in RRMS		(20)
		Bacteroidia	Bacteroidales	Bacteroidaceae	Bacteroides		Decreased in MS		(19)
				Porphyromonadaceae	Parabacteroides		Decreased in MS		(20)
					Butyricimonas		Decreased in MS	Involved in SCFA production	(21, 76)
				Prevotellaceae	Prevotella		Decreased in MS	Linear negative relationship with the intestinal Th17 frequency	(86)
					Paraprevotella		Decreased at MS onset		(87)
	Firmicutes	Clostridia	Clostridiales	Lachnospiraceae	Blautia		Increased in RRMS		(20)
					Blautia		Decreased at MS onset		(87)
					Dorea		Increased in RRMS		(20)
				Ruminococcacceae	Faecalibacterium		Decreased in MS	Positively associated with SCFA production and negatively with TNF-α levels	(19, 80)
					Anaerotruncus		Decreased at MS onset		(87)
					Subdoligranulum		Decreased at MS onset		(87)
					Unclassified		Increased in PPMS		(85)
				Ruminococcaceae			Decreased in pediatric MS		(25)
			Eubacteriales	Oscillospiraceae	Flavonifractor	Flavonifractor plautii	Increased in MS	Affects CD4+ T cells and IL-17	(88–90)
				Lachnospiraceae			Decreased in pediatric MS		(25)
		Clostridium cluster IV and XIVa					Decreased in MS	Affects SCFAs, Tregs, and anti-inflammatory cytokine production	(19)
		Bacilli	Lactobacillales	Streptococcaceae	Streptococcus	Streptococcus thermophilus	Increased in MS		(19)
						Streptococcus salivarius	Increased in MS		(19)
						Streptococcus oralis	Increased in MS		(86)
						Streptococcus mitis	Increased in MS	Promotes Th17 differentiation and participates in cell-mediated tissue damage in autoimmunity	(86, 91)
		Negativicutes	Selenomonadales	Veillonellaceae	Megasphaera		Decreased at MS onset		(87)
					Mitsuokella		Decreased at MS onset		(87)
				Lactobacillaceae	Lactobacillus		Decreased in MS		(20)
	Verrucomicrobia	Verrucomicrobiae	Verrucomicrobiales	Akkermansiaceae	Akkermansia		Increased in MS	Associated with SCFA production and pro-inflammatory effects	(21, 81, 82)
						Akkermansia muciniphila	Increased in PPMS		(85)
	Actinobacteria	Coriobacterideae	Coriobacteriales	Coriobacteriaceae	Eggerthella	Eggerthella lenta	Increased in MS		(19)
					Collinsella		Decreased in MS		(20, 21)
					Adlercreutzia		Decreased in MS	Affects M2 polarization, IL-10 expression in M2 macrophages, and inhibition of CD4+ T-cell priming by DCs	(20, 92)
Archaea	Euryarchaeota	Methanobacteria	Methanobacteriales	Methanobacteriaceae	Methanobrevibacter		Increased in MS	Recruitment of inflammatory cells and DCs	(21, 93)
Heunggongvirae	Uroviricota	Caudovirales					Increased in MS		(88)

Shown are the sets of microorganisms altered in MS, MS onset, RRMS, PPMS, and pediatric MS. Along with their abundance in MS, their role in the immune system is also reported.

RRMS, relapsing–remitting multiple sclerosis; PPMS, primary progressive multiple sclerosis; SCFA, short-chain fatty acid; DCs, dendritic cells.