Subsequently,biofilm formation of the C. tropicalis strains in each well was determined by a crystal violet binding assay as described before (O'Toole,2011). Biofilm formation on the well without addition of anymicroorganism was used as a negative control. Biofilm formation inwells without any essential oil, were used as a positive control and setas 100%. Decrease (%) in biofilm formations relative to the positivecontrol, was calculated using the following equation: