Butyrate inhibits the growth of C. difficile strain 630. (A) Growth curves [log10(OD600)] over 24 h (n = 7 per condition). (B) CFUs after 24 h (n = 21 per condition) and (C) at 6, 12, 18, and 24 h of growth in BHI supplemented with 5 and 25 mM acetate, propionate, or butyrate (n > 15 per condition). (D) Growth curves [log10(OD600)] over 24 h in BHI supplemented with increasing concentrations of butyrate (0, 5, 10, 25, 50 mM; n = 3 per condition). Statistical significance calculated using Dunnett’s test: *P-value <0.05; **P-value <0.01; ***P-value <0.001.