Fig. 1.

The inhibition of biofilm growth and eradication of established biofilm by NAg, ionic silver (Ag⁺) and gentamicin (GM). A A schematic of biofilm growth stages. B Determination of the minimum inhibitory concentration (MIC, defined as the lowest concentration that resulted in no visual growth) of NAg (tested at 0.5–7 µg/mL), Ag⁺ (0.5–7 µg/mL) and gentamicin (1–8 µg/mL) on P. aeruginosa general growth (24 h exposure at 37 °C). Red and blue boxes represent the untreated cell-only and the media-only controls, respectively. Effect of NAg, Ag⁺ and GM on C P. aeruginosa biofilm formation (24 h exposure, 37 °C), determining the minimum biofilm inhibitory concentration (MBIC, defined as the lowest concentration that caused ≥ 80% biofilm growth inhibition) and on D grown P. aeruginosa biofilm (24 h exposure, 37 °C), determining the minimum biofilm eradication concentration (MBEC, defined as the lowest concentration that caused ≥ 80% reduction of pre-formed biomass). Biofilm biomass is expressed as % relative to the cell-only control (no antimicrobial agent, 0 µg/mL). Error bars represent SEM (standard error of the mean) of three biological replicates (experiments with independent bacterial inocula from three isolates and different antimicrobial preparations, each with three technical replicates). * indicates statistically significant inhibition and eradication effects with p > 0.05 (not significant, ns), p < 0.05 (*), p < 0.01 (**), p < 0.001 (***) and p < 0.0001 (****), relative to the cell-only control