三种植物精油对美人鱼发光杆菌美人鱼亚种的抑菌效果及其毒力基因表达的影响

为研究百里香精油、牛至精油和肉桂精油对海水养殖重要致病菌美人鱼发光杆菌美人鱼亚种（Photobacterium damselae subsp．damselae，PDD）的抑菌作用，采用二倍稀释法分别测定3种植物精油对6株不同致病力PDD菌株的最小抑菌质量浓度（MIC）和最小杀菌质量浓度（MBC）。采用分光光度计法检测添加精油后6株PDD生长曲线的变化；以2株高致病性PDD菌株为研究对象，分析不同浓度精油对PDD毒力基因表达量及胞外产物（extracellular products，ECP）活性的影响；分析了3种精油存储不同时间后以及在金属离子影响下的药效稳定性。结果显示，这3种精油对6株PDD菌株均具有较好的抑菌及杀菌作用，MIC为32～128 μg/mL，MBC为64～192 μg/mL；3种精油对2株高致病性PDD菌株的毒力基因表达及ECP的磷脂酶活性和溶血活性均有抑制作用，其中低浓度精油对PDD主要毒力基因的抑制作用最明显。3种精油于室温下避光存储35 d，对实验菌株的杀菌率均大于99%，显示其良好的药物稳定性；水环境中不同浓度Na+、Mg2+、Ca2+、K+等对3种精油的杀菌效果无明显影响。研究表明，3种精油均适宜开发为防治水产动物细菌性疾病的新型渔药或饲料添加剂。本研究可为拓展芳香类植物精油在水产疾病防控上的应用提供借鉴与参考。

The bactericidal efficacy of three plant essential oils against Photobacterium damselae subsp.damselae and their impact on the expression of virulence genes

The study was to investigate the bactericidal efficacy of Thyme essential oil, Oregano essential oil and Cinnamon essential oil on Photobacterium damselae subsp. damselae (PDD), an important pathogenic bacteria in mariculture. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of three plant essential oils against six PDD strains with different pathogenicity were determined through double dilution method. These strains’ growth curve after adding plant essential oil was detected using spectrophotometric method. The expression of virulence genes and activity of extracellular products (ECP) under different essential oil concentrations in two highly pathogenic PDD strains were analyzed. Meanwhile, The bactericidal efficacy of three plant essential oils after long-time storage and metal ions addition were studied. The results showed that the three plant oils had good bactericidal effects on six PDD strains, with MICs of 32-128 μg/mL and MBCs of 64-192 μg/mL. They had good had inhibitory effects on the expression of virulence genes, phospholipase activity and hemolytic activity of ECP in two highly pathogenic PDD strains. Specifically, low concentration of plant essential exhibited significantly inhibitory effects on the expression of virulence genes. After 35 days of storage away from light, the sterilization rates of the three essential oils remained above 99%, demonstrating excellent pharmacodynamic stability. The presence of different concentrations of Na+, Mg2+, Ca2+, K+ in the water environment did not exert a significant influence on the bactericidal efficacy of the three essential oils. The results showed the suitability of the three essential oils for the development of novel drugs or feed additives in aquaculture, with potential application in disease prevention and treatment. This study can provide reference for expanding the application of aromatic plant essential oil in the prevention and control of aquatic diseases.