中链脂肪酸的抗菌作用：辛酸对悉生卤虫无节幼体接种虾致病菌哈维氏弧菌和副溶血性弧菌的抗菌作用

Antibacterial effect of medium-chain fatty acid: caprylic acid on gnotobiotic Artemia franciscana nauplii against shrimp pathogens Vibrio harveyi and V. parahaemolyticus

试验目的是测定辛酸对培养基中的卤虫无节幼体接种了虾病原菌哈维氏弧菌和副溶血性弧菌的抗菌作用。首先,通过细菌生长试验研究不同浓度的辛酸（1,10和100 mM）对哈维氏弧菌和副溶血性弧菌抗菌效果。研究表明,100 mM浓度的辛酸,在5 h内病原体被完全抑制生长,然而,1 mM和10 mM浓度,有效的抑制时间延长。接着,通过细菌生长试验研究不同pH值（5~7）对辛酸（浓度为10 mM）抑制哈维氏弧菌和副溶血性弧菌抗菌效果的影响。与pH值6和7比较,在pH值5时,病原体生长非常少。卤虫无节幼体（龄II）饲养在含有10 mM辛酸的培养基中,然后接种哈维氏弧菌和副溶血性弧菌,记录60 h内的死亡率,每间隔6 h记录1次。研究发现,接种了哈维氏弧菌和副溶血性弧菌的卤虫无节幼体的死亡率分别降低到20.61%和16.3%。研究结果表明,辛酸对水产养殖中的发光弧菌具有潜在的抗菌活性。

The present study was carried out to determine the antibacterial effect ofcaprylic acid in the culture system of Artemia franciscana naupliiinoculated with shrimp pathogens Vibrio harveyi and V. parahaernolyticus. To begin with, the antibacterial effect of different concentrations （1, 10 and 100 mM） of caprylic acid against V. harveyi and V. parahaemolyticus was assessed through bacterial growth study. This indicated that at 100 mM concentration, the growth of the pathogens was completely inhibited within 5 h, whereas, in 1.0 and 10 mM concentrations, effective inhibition was observed with the extension of time. Subsequently, the influence of pH variation on the growth inhibitory effect of 10 mM caprylic acid against V. harveyi and V. parahaemolyticus at different pH （5-7） was also made through bacterial growth study. At pH 5, the pathogen growth was very less, compared with pH 6 and 7. The Artemia nauplii （instar Ⅱ） reared in 10 mM caprylic acid supplemented medium were challenged with V. harveyi and V. parahaemolyticus, and the mortality was recorded at an interval of 6 h up to 60 h. In this study, the mortality of Arternia nauplii reduced to 20.61 % and 16.30% in V. parahaernolyticus and V. harveyi challenged groups, respectively. The present results provide evidence for the potential antibacterial activity of caprylic acid in aquaculture against luminescent vibrios.