Figure 1
Carvacrol inhibits the growth of planktonic Streptococcus pyogenes in a concentration-dependent manner. (A) The chemical structure of carvacrol. (B) Inhibition of growth of S. pyogenes strains (ATCC 19615, ATCC 49399, a clinical isolate from a pharyngeal patient and an erythromycin-resistant Spy 1558) by carvacrol at the given concentrations was measured using micro-broth dilution assay in BHI broth after 24 h of incubation at 37 °C. Bacterial turbidity was measured at OD = 600 nm, and percentage growth inhibition is expressed relevant to the vehicle (0.25% DMSO) as the mean ± SE of three independent experiments. Statistical analysis was performed using one-way ANOVA, and the differences among means were compared using Tukey’s test; *P < 0.05, **P < 0.01, and ***P < 0.001. (C) Bactericidal concentrations of carvacrol for S. pyogenes strains were determined by inoculating on agar plate from each replicates well in broth dilution plate that shows a complete absence of growth and was incubated at 37 °C for 24 h. Concentrations labeled as 2, 3, 4, 5, and 6 on the agar plate represent carvacrol concentration of 2000, 1000, 500, 250, and 125 µg/mL, respectively. Arrows indicate the MBCs observed. MBC, Minimum bactericidal concentration.
