Department of Plant, Food, and Environmental Sciences, Faculty of Agriculture, Dalhousie University, Truro, NS, Canada.
Department of Biology, Faculty of Science, Dalhousie University, Halifax, NS, Canada.
Sci Rep. 2021 Jan 15;11(1):1487. doi: 10.1038/s41598-020-79713-0.
Streptococcus pyogenes is an important human pathogen worldwide. The identification of natural antibacterial phytochemicals has renewed interest due to the current scarcity of antibiotic development. Carvacrol is a monoterpenoid found in herbs. We evaluated carvacrol alone and combined with selected antibiotics against four strains of S. pyogenes in vitro. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of carvacrol against S. pyogenes were 125 µg/mL (0.53 mM) and 250 µg/mL (1.05 mM), respectively. Kill curve results showed that carvacrol exhibits instantaneous bactericidal activity against S. pyogenes. We also demonstrated the potential mechanism of action of carvacrol through compromising the cell membrane integrity. Carvacrol induced membrane integrity changes leading to leakage of cytoplasmic content such as lactate dehydrogenase enzymes and nucleic acids. We further confirmed dose-dependent rupturing of cells and cell deaths using transmission electron microscopy. The chequerboard assay results showed that carvacrol possesses an additive-synergistic effect with clindamycin or penicillin. Carvacrol alone, combined with clindamycin or penicillin, can be used as a safe and efficacious natural health product for managing streptococcal pharyngitis.
化脓链球菌是一种重要的人类病原体，目前抗生素的开发十分匮乏，因此天然抗菌植物化学物质的鉴定重新引起了人们的兴趣。香芹酚是一种存在于草药中的单萜烯。我们评估了香芹酚单独使用和与选定抗生素联合使用对体外 4 株化脓链球菌的效果。香芹酚对化脓链球菌的最低抑菌浓度（MIC）和最低杀菌浓度（MBC）分别为 125µg/mL（0.53mM）和 250µg/mL（1.05mM）。杀菌曲线结果表明，香芹酚对化脓链球菌具有即时杀菌活性。我们还通过破坏细胞膜完整性来证明香芹酚的潜在作用机制。香芹酚诱导细胞膜完整性改变，导致细胞质内容物（如乳酸脱氢酶酶和核酸）泄漏。我们进一步使用透射电子显微镜证实了细胞的剂量依赖性破裂和细胞死亡。棋盘试验结果表明，香芹酚与克林霉素或青霉素具有相加-协同作用。香芹酚单独使用，或与克林霉素或青霉素联合使用，可作为一种安全有效的天然保健品，用于治疗链球菌性咽炎。
