College of Animal Science and Technology, Yangzhou University, Yangzhou, 225009, China; Research Center of Characteristic Fish, Freshwater Fisheries Research Institute of Jiangsu Province, Nanjing, 210017, China.
College of Animal Science and Technology, Yangzhou University, Yangzhou, 225009, China.
Fish Shellfish Immunol. 2022 Jun;125:180-189. doi: 10.1016/j.fsi.2022.05.009. Epub 2022 May 11.
Aeromonas veronii is a freshwater bacterium associated with many diseases in aquatic animals. However, few cases of A. veronii infection were reported in Odontobutis potamophila, which has been becoming a promising fish species in China in recent years. In this study, the dominant bacteria were isolated from diseased O. potamophila showing signs of hemorrhage on fins, ulceration on the dorsal and abdomen. The representative isolate Stl3-1was identified as A. veronii based on analysis of its morphological, physiological, and biochemical features, as well as 16S rRNA and gyrB gene sequences. The median lethal dosage (LD) of the isolate Stl3-1 for O. potamophila was determined as 4.5 × 10 CFU/mL. Histopathological analysis revealed that the isolate Stl3-1caused considerable histological lesions in the fish, including tissue cell degeneration, necrosis, and inflammatory cell infiltrating. Detection of virulence-related genes showed that A. veronii Stl3-1 was positive for exu, ompA, lip, flaH, hlyA, aer, flgM, tapA, act, flgA, gcaT and flgN. Additionally, quantitive real-time PCR (qRT-PCR) was also undertaken to analyses the host defensive response in O. potamophila infected by A. veronii. The immune-related gene expressions in O. potamophila during experimental infection were monitored at different point of time, and the results showed that the expression levels of MHC II, Myd88, TLR, and SOD were significantly up-regulated in liver, gill, spleen, and head kidney. The results revealed that A. veronii was a pathogen causing mass mortalities of O. potamophila and will contribute to better understanding the host defensive response against A. veronii infection.
维氏气单胞菌是一种与水生动物多种疾病相关的淡水细菌。然而，在近年来在中国成为有前途的鱼类品种的波氏吻鲈中，很少有报道称其感染了维氏气单胞菌。在本研究中，从出现鳍部出血、背部和腹部溃疡等症状的患病波氏吻鲈中分离出优势细菌。代表性分离株 Stl3-1 基于其形态、生理和生化特征以及 16S rRNA 和 gyrB 基因序列的分析，被鉴定为维氏气单胞菌。分离株 Stl3-1 对波氏吻鲈的半数致死剂量（LD）为 4.5×10 CFU/mL。组织病理学分析表明，分离株 Stl3-1 对鱼类造成了相当大的组织损伤，包括组织细胞变性、坏死和炎性细胞浸润。毒力相关基因检测表明，维氏气单胞菌 Stl3-1 携带 exu、ompA、lip、flaH、hlyA、aer、flgM、tapA、act、flgA、gcaT 和 flgN 等基因。此外，还进行了定量实时 PCR（qRT-PCR）分析，以研究波氏吻鲈感染维氏气单胞菌后的宿主防御反应。在实验感染期间，监测了不同时间点波氏吻鲈免疫相关基因的表达，结果表明，MHC II、Myd88、TLR 和 SOD 的表达水平在肝脏、鳃、脾脏和头肾中显著上调。结果表明，维氏气单胞菌是导致波氏吻鲈大量死亡的病原体，并将有助于更好地理解宿主对维氏气单胞菌感染的防御反应。
