Effects of niclosamide on P. aeruginosa motility and biofilm formation. (A to C) Swimming (A), swarming (B), and twitching (C) by P. aeruginosa PA14 in the presence of increasing concentrations of niclosamide. (D) Biofilm formation by P. aeruginosa PA14 in the presence of increasing concentrations of niclosamide, assessed as the amount of attached cells (gray histograms, left axis) versus planktonic cells (black squares, right axis). Values are the means (± standard deviations) of at least three independent experiments. **, P < 0.01; ***, P < 0.001 (ANOVA).