Cell suspensions (100μL) were transferred into 96-well microtiter polystyrene plates (Greiner Bio-One, Germany), incubated at 28 °C for 240 min in an orbital mixer incubator, and stained for 15 min at room temperature using 100 μL of 0.1% crystal violet solution. After washing with sterile water to remove unattached cells and residual dye, 100 μLof 95% ethanol was added to solubilize the dye adsorbed by biofilm.