Department of Pathobiology, Faculty of Veterinary Science, Bu-Ali Sina University, Hamedan, Iran.
Department of Microbiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
J Appl Microbiol. 2018 Feb;124(2):379-388. doi: 10.1111/jam.13639. Epub 2018 Jan 11.
The present study was conducted to investigate the effects of Thymus daenensis and Satureja hortensis essential oils (EOs) on the planktonic growth, biofilm formation and quorum sensing (QS) of some Staphylococcus aureus isolates (strong biofilm producers).
Minimum inhibitory concentration (MIC) of the EOs, inhibition of biofilm formation as well as disruption of preformed Staph. aureus biofilms were assessed. The antibiofilm activity of the EOs was determined using microtitre plate test (MtP) and scanning electron microscope (SEM). The QS inhibitory activity was also examined on the pregrown biofilms by gene expression analysis using quantitative real-time RT-polymerase chain reaction (PCR) of hld gene (RNAIII transcript). Moreover, tetrazolium-based colorimetric assay (MTT) was performed to detect cytotoxic effects of these EOs on the Vero cell line. Finally, the major components of the tested EOs were determined using Gas Chromatography-Mass Spectrometry (GC-MS). The MICs of T. daenensis and S. hortensis EOs against planktonic cells of the isolates were 0·0625 and 0·125 μl ml respectively. The minimum bactericidal concentrations for both of the EOs was 0·125 μl ml . The MtP test showed a significant inhibitory effect of the EOs on the biofilm formation and disruption at sub-MIC concentrations. These results were confirmed by SEM. Real-time PCR revealed a significant down-regulation of hld gene following treatment with MIC/2 concentration of S. hortensis EO. GC-MS analysis showed that carvacrol, terpinene and thymol were the major components of the applied EOs.
As selected EOs did not show significant cytotoxic effects even up to tenfold of MIC concentration, the applied EOs seem to be good candidates for preventing of biofilm formation of Staph. aureus cells.
The present study introduced T. daenensis and S. hortensis EOs as new antibiofilm, and S. hortensis EO as anti-QS herbal agents with natural origin against Staph. aureus.
本研究旨在探讨藏茴香和香薄荷精油（EOs）对一些金黄色葡萄球菌分离株（强生物膜产生菌）浮游生长、生物膜形成和群体感应（QS）的影响。
测定了 EOs 的最小抑菌浓度（MIC）、抑制生物膜形成以及破坏已形成的金黄色葡萄球菌生物膜的能力。使用微量滴定板试验（MtP）和扫描电子显微镜（SEM）测定了 EOs 的抗生物膜活性。通过定量实时 RT-聚合酶链反应（PCR）检测基因表达分析，在预培养生物膜上还检查了 EOs 的 QS 抑制活性hld 基因（RNAIII 转录物）。此外，还通过四唑基比色法（MTT）检测这些 EOs 对 Vero 细胞系的细胞毒性作用。最后，使用气相色谱-质谱联用（GC-MS）法测定了测试 EOs 的主要成分。藏茴香和香薄荷精油对分离株浮游细胞的 MIC 分别为 0.0625 和 0.125 μl/ml。两种 EOs 的最低杀菌浓度均为 0.125 μl/ml。MtP 试验表明，EOs 在亚 MIC 浓度下对生物膜形成和破坏具有显著的抑制作用。扫描电镜证实了这一结果。实时 PCR 显示，香薄荷精油 MIC/2 浓度处理后 hld 基因表达显著下调。GC-MS 分析表明，香芹酚、萜品烯和百里香酚是应用 EOs 的主要成分。
由于所选 EOs 即使在 MIC 浓度的十倍以上也没有显示出显著的细胞毒性作用，因此应用 EOs 似乎是预防金黄色葡萄球菌细胞生物膜形成的良好候选物。
本研究介绍了藏茴香和香薄荷精油作为新的抗生物膜形成剂，以及香薄荷精油作为天然来源的抗 QS 草药剂，可对抗金黄色葡萄球菌。
