黄颡鱼败血症病原菌的分离鉴定与病理组织学观察

Identification of Pathogenic Bacteria for Septicemia in Yellow Catfish (Pelteobagrus fulvidraco Richardson) and Their Histological Observation

该研究对重庆市璧山县大路渔场大规模发生败血症的患病黄颡鱼的病原菌进行分离鉴定及组织病理学观察.首先把从患病黄颡鱼脾脏中分离获得的优势菌(命名为YC-1)人工感染健康黄颡鱼,该鱼患病症状表现与自然发病症状一致.再从人工感染鱼脾脏中分离病原菌,再次感染健康黄颡鱼,其症状仍然与自然发病症状一致.因此确认分离菌株YC-1为黄颡鱼"败血症"的致病菌.根据菌株形态学特点、生理生化指标和16SrDNA基因序列鉴定其为嗜水气单胞菌Aeromonas hydrophila.组织病理切片显示患病黄颡鱼肝组织严重坏死,肝细胞排列紊乱;脾脏细胞间界限不清,细胞核膨大;肾小管上皮细胞肿胀,肾小囊腔间隙增大.

The study focused on the bacteriological and histopathological examination of septicemia in yellow catfish,Pelteobagrus fulvidraco Richardson,during the fish disease outbreaks in a quaculture farm in BiShan county of Chongqing.One bacteria strain was isolated from the spleen of diseased yellow catfish samples with the typical septicemia symptoms and was named YC-1.Then a challenge experiment was carried out with healthy yellow catfish by means of injection of the bacteria.The symptoms of the artificially infected fish were similar to those of the natural diseased fish.The pathogenic bacteria were isolated again from the spleen of the artificially diseased fish and were used in infection of healthy yellow catfish.As a result,symptoms were observed which were similar to the symptoms of the natural diseased fish.Therefore,YC-1 was identified as the pathogenic bacterium strain of the diseased fish.According to its physiological feature,biochemical indexes and 16S rDNA sequence,YC-1 was further proved to be Aeromonas hydrophila.Histopathological examination of the diseased fish showed necrosis of hepatocytes with seriously disordered arrangement of the cells;unclear cell boundary and swollen nucleus in the lymphocytes of the spleen and hydropic swelling and degeneration of renal tubular epithelia in the kidney.