Table 1.

Metabolites that contribute to pathogenesis

A. Metabolites enhance pathogen expansion
Metabolite	Source	Pathogen	References
Sialic Acid	Released from mucosa by microbiota	S. typhimurium, C. difficile	Ng et al. 2013
Succinate	By-product of microbiota fermentation	C. difficile	Ferreyra et al. 2014
Hydrogen	By-product of microbiota fermentation	S. typhimurium	Maier et al. 2013
Ethanolamine	Mammalian and bacterial membranes	EHEC, S. typhimurium, L. monocytogenes	Kendall et al. 2012; Bertin et al. 2011; Thiennimitr et al. 2011; Joseph et al. 2006
Sorbitol	Host diet	C. difficile	Theriot et al. 2014

B. Metabolites influence virulence gene expression
Metabolite	Virulence factor controlled	Regulator(s) involved	References
ethanolamine	Enhances LEE expression (EHEC)	EutR	Kendall et al. 2012
Succinate	Enhances LEE expression (EHEC)	Cra	Curtis et al. 2014
Fucose	Inhibits LEE expression (EHEC)	FusKR two component system	Pacheco et al. 2012
Butyrate	Inhibits SPI-1 expression (S. typhimurium)	unknown	Lawhon et al. 2002; Gantois et al. 2006; Hung et al. 2013
	Enhances LEE expression (EHEC)	Lrp → PchA → LeuO → Ler	Nakanishi et al. 2009; Takao et al. 2014; Tobe et al. 2011
	Enhances flagella expression (EHEC)	Lrp & unknown Lrp-independent pathway	Tobe et al. 2011
Propionate	Inhibits SPI-1 expression (S. typhimurium)	HilD → HilA	Lawhon et al. 2002; Gantois et al. 2006; Hung et al. 2013
Acetate	Enhances SPI-1 expression (S. typhimurium)	BarA/SirA two component system → HilA	Lawhon et al. 2002
Taurocholate	Enhances C. difficile germination		Theriot et al. 2014