Suppression of USA300 growth by butyric acid and acetic acid. USA300 (106 CFU/ml) was incubated with butyric acid (A, B) or acetic acid (C, D) (0.02–100 mM in PBS) overnight. Incubation of USA300 with PBS served as controls (c). After incubation, USA300 was diluted 1:100–1:105 with PBS, and 5 μl of the dilutions were spotted on an agar plate for MBC assays (A, C). The CFU counts were illustrated as the mean ± SD of three independent experiments (B, D). ***P<0.001 (two-tailed t-tests). UD, undetectable.