The preparation of agar, broth, and bacteria were carried out as described in Section 3.7. MICs was determined for thyme, clove, and tea tree against S. aureus and E. coli according to the method used by Zhang and Mith [53,54] with some minor modifications. The original solution of each EO was dissolved in Tween-20 (0.5%), dimethyl sulfoxide (DSMO, 5%), or ethanol (100%) in a 1:1 ratio to make serial 2-fold dilutions, yielding solutions with a gradient from 100% oil to 0.2% oil (v/v). A volume of 10 µL of each oil dilution was added to the 6 mm paper disc and then placed on MH agar plates with a 100 µL bacterial concentration containing a 104–105 CFU/mL suspension of each tested bacterium. DSMO without bacteria was used as a control.