*2.7. Minimum Inhibitory Concentration (MIC) and Minimum Bactericide Concentration (MBC) Assays*

Minimum inhibitory concentration (MIC) and minimum bactericide concentration (MBC) were determined according to the method described by Elshikh et al. with minor adjustment [25]. Briefly, 100 μL of MH broths were added into 96-well plate and then another 100 μL of dissolved samples, whose initial concentrations were 100 mg/mL, were added in first wells. Serial two-fold dilutions were made with final concentrations ranging from 50 mg/mL to 0.39 mg/mL. Afterwards, 100 μL of the standardized bacteria suspensions (1 <sup>×</sup> 106 CFU/mL) was added to each test well, so that the final

volume in each well was 200 μL. Plates were incubated at 37 ◦C for 24 h. After incubation, 30 μL of the freshly prepared resazurin (0.015%) was added to all test wells, and further incubated for 2 h to allow the viable microorganism to metabolize the blue resazurin dye into pink resorufin. MIC was defined as the concentration at which the corresponding well showed no color change. Afterwards, the contents of wells with concentrations equal or higher than MIC values were directly incubated onto the MH plate, and the lowest concentration at which there was no colony growth was defined as MBC.
