4.3. Quantitative Absorbance-Based Biofilm Measurement (Crystal Violet Assay)

The cultures were treated with EGCG-S and antibiotics alone and different formulations followed up by incubation at 37 °C for 4 days. The liquid was aspirated, the biofilm (if any) was washed and then stained with 0.1% crystal violet (CV) for 24 h. After strain aspiration and a final 1 × PBS wash, the biofilms were dried for 24 h. Biofilm was resuspended in 30% acetic acid and the optical density (OD) were recorded at 595 nm [76]. All experiments were performed in triplicate, with mean and standard deviation calculated. These readings were then used to determine the percentage of biofilm inhibition. 10% bleach and PBS were used as the positive and negative control, respectively.