FIG 1.

Identification of a small molecule that is antimicrobial to S. aureus. (A) Workflow for identifying compounds of interest. (B) Percent growth inhibition by treatment with the indicated concentrations of compound ‘921 relative to vehicle control for S. aureus Newman or ΔmntH/C strain. Data are mean ± standard deviation from duplicate measurements. Statistical significance was determined by t test where * = P < 0.05 and ** = P < 0.01. (C) Relative growth at 12 h with 5 μM ‘921 ± MnCl₂ is graphed as % of growth without compound or MnCl₂. Data are mean ± standard deviation from triplicate measurements acquired on two separate days and combined (n = 6). Statistical significance was determined by one-way analysis of variance (ANOVA) with Dunnett’s multiple-comparison test comparing each concentration of Mn to no-Mn control where *** = P < 0.001. (D) CFU recovered at 2-h intervals from growth curve of S. aureus Newman treated with vehicle, 5 μM ‘921, or 5 μM ‘921 + 1 mM MnCl₂ over time. Data are mean ± standard deviation from quadruplicate measurements. (E) CFU recovered following 24-h treatment of mid-exponential-phase S. aureus Newman cultures with the indicated combinations of vehicle, 1 mM MnCl₂, 100 μM ‘921, and 1 mM EDTA. Data are mean ± standard deviation from triplicate measurements acquired on two separate days combined (n = 6). Statistical significance was determined by one-way ANOVA with Sidak’s multiple-comparison test comparing each concentration of Mn to no-Mn control where * = P < 0.05 and *** = P < 0.001. Experiments in panels F and G were performed in an anaerobic chamber. (F) Growth of S. aureus Newman in the presence of vehicle, 1 mM MnCl₂, 5 μM ‘921, or 5 μM ‘921 + 1 mM MnCl₂. Data are mean ± standard deviation for triplicate measurements. (G) CFU recovered following treatment of mid-exponential-phase cultures of S. aureus with vehicle, 1 mM or 100 μM MnCl₂, 100 μM ‘921, or combinations of MnCl₂ + ‘921 for 24 h. Data are mean ± standard deviation for triplicate measurements.