Figure 2.

Carvacrol exerts concentration-dependent growth inhibition on Streptococcus pyogenes and an instantaneous bactericidal effect at 2 × MIC. Time-kill curve plots from (A) agar plate count method* and (B) spectrophotometric method** on the growth of Streptococcus pyogenes ATCC 19615, clinical isolate, and erythromycin-resistant, Spy 1558 in the presence of ¼ × MIC ½ × MIC, 1 × MIC, and 2 × MIC of carvacrol or 0.25% DMSO (diluent control) and no treatment (bacteria control). The bacteria and carvacrol solutions were prepared in BHI broth and were assessed for a period of 24 h at a 37 °C incubation period. *Cell growth/killing at 0.08, 1, 2, 3, 4, 5, 6, and 24 h incubation was measured by performing viable cell counts by dilution of cultures in saline solution (0.85% NaCl) and enumeration on BHI agar plates in duplicate. **The bacterial turbidity at OD = 600 nm was measured using a spectrophotometer in 1 h intervals over 24 h incubation period with different carvacrol concentrations or diluent in triplicate. Both methods were performed in three independent experiments. “0” in the scale represents “below the limit of detection”.