The working solutions (10 mg/mL) were diluted with MBH in the ratio of 1:25 and then 50 μL were transferred into sterile microtiter plates. 50 μL of bacterial inocula were added into the microtiter plates. The final concentrations of test substances in microtiter plates were 200 μg/mL. Plates were incubated at 35 ◦C (15 hours), and then 20 μL of 0.09% resazurin was added into each well. Plates were further incubated at 3 ◦C (3 hours) for complete incubation.