Department of Microbiology, Teaching Institute of Public Health of Primorsko-Goranska County, Rijeka, Croatia.
Department of Microbiology and Parasitology, Faculty of Medicine, University of Rijeka, Rijeka, Croatia.
J Med Microbiol. 2019 May;68(5):703-710. doi: 10.1099/jmm.0.000962. Epub 2019 Mar 27.
The present study evaluated the possible synergistic antimycobacterial interactions of Juniperus communis and Helichrysum italicum essential oils (EO).
Antimycobacterial potential was tested against Mycobacterium avium and Mycobacterium intracellulare using broth and water dilution method and checkerboard synergy method. Antiadhesion and antibiofilm effect of EOs was evaluated on biotic (HeLa cells) and abiotic surface (polystyrene). To evaluate the possible mechanisms of action, cellular leakage of proteins and DNA was tested and structural changes were visualized with a transmission electron microscope.
MIC, minimum bactericidal concentration (MBC) and minimal effective concentration (MEC) were 1.6 mg ml for J. communis EO and 3.2 mg ml for H. italicum EO against both mycobacteria. All combinations of EOs in checkerboard synergy method produced fractional inhibitory concentration index values ranging from 0.501 to 1.5, corresponding to synergistic, additive or indifferent effects. Mycobacterium avium showed a greater tendency to create biofilm but these EOs at subinhibitory concentrations (sMIC) effectively blocked the adhesion and the establishment of biofilm. The exposure of both mycobacteria to MICs and sMICs lead to significant morphological changes: acquired a swollen form, ghost-like cell, disorganized cytoplasm detached from the cell wall. OD value of supernatant for both mycobacteria exposed to EOs have confirmed that there is a leakage of cellular material.
The leakage of the cellular material is noticeably higher in sMIC, which is probably due to cell wall damage. sMIC of both EOs have an additive or synergistic effect, reducing MICs, limiting adhesion and preventing the formation of biofilms.
本研究评估了杜松和蜡菊精油（EO）对分枝杆菌协同抗分枝杆菌作用的可能性。
采用肉汤稀释法和水稀释法以及棋盘协同法检测抗分枝杆菌潜能，检测 EO 对生物（HeLa 细胞）和非生物表面（聚苯乙烯）的抗黏附和抗生物膜作用。为了评估可能的作用机制，检测了细胞蛋白质和 DNA 的渗漏，并使用透射电子显微镜观察结构变化。
MIC、最小杀菌浓度（MBC）和最小有效浓度（MEC）分别为 1.6mg/ml 对 J. communis EO 和 3.2mg/ml 对 H. italicum EO 对两种分枝杆菌均有效。棋盘协同法中所有 EO 组合的部分抑菌浓度指数值均在 0.501 至 1.5 之间，对应于协同、相加或无关作用。分枝杆菌 avium 更倾向于形成生物膜，但这些 EO 在亚抑菌浓度（sMIC）下有效阻止了黏附和生物膜的形成。分枝杆菌暴露于 MIC 和 sMIC 下会导致明显的形态变化：细胞呈肿胀形式，呈幽灵状，细胞质失去与细胞壁的连接而变得紊乱。暴露于 EO 的两种分枝杆菌的上清液 OD 值均证实细胞物质有渗漏。
sMIC 下细胞物质的渗漏明显更高，这可能是由于细胞壁受损。两种 EO 的 sMIC 具有相加或协同作用，降低 MIC，限制黏附并防止生物膜形成。
