摘要
从天然患病南方鲇(Silurus meridionalisChen)幼鱼的肝脏中分离获得1株优势菌,命名为SCL1。用该菌株人工感染健康南方鲇幼鱼,发现菌株SCL1的感染致死率高,且患病症状与自然发病症状一致。再从人工感染的患病鱼肝脏中分离病原菌,再次感染健康南方鲇幼鱼,其症状与自然发病症状一致,确认分离菌株为南方鲇"败血症"的致病菌。该菌株形态学、生理生化特征和16S rDNA基因序列显示其为嗜水气单胞菌(Aeromonas hydrophila)。药敏试验结果表明,该菌对土霉素、链霉素、氧氟沙星、氟哌酸、卡那霉素和庆大霉素高度敏感,而对青霉素钠、麦迪霉素、罗红霉素、甲氧苄啶、乙酰螺旋霉素不敏感。组织病理研究显示患病南方鲇肝组织严重坏死,肝细胞排列紊乱,部分肝细胞核肿胀、崩解;脾脏细胞间界限不清,细胞核膨大,核内染色质疏松;肾小管上皮细胞肿胀,肾小囊腔间隙增大,可见该菌主要损伤南方鲇幼鱼肝、肾和脾。本研究旨在为南方鲇细菌性败血症的诊断与防治提供科学依据。
The study focused on bacteriological and histopathological examination of septicemia in juvenile southern catfish,Silurus meridionalis,when the disease took place in the catfish farm in Chongqing.There were 15%-40% of cultured southern catfish suffering from the disease and the mortality rate was 45%-80%.The diseased individuals exhibited traits of hemorrhagic septicemia,and showed symptoms of emaciation,sluggishness,eye exophthalmia,and fin hemorrhages.The viscera symptoms of the diseased fish included ascites,liver swelling,and clear histopathological alterations in spleen and kidney.Histopathological examination revealed hydropic swelling of hepatocytes,degeneration and necrosis of renal tubular epithelia in kidney,tumidity in lymphocytes in spleen.One strain of a bacterial species was isolated from liver,kidney and spleen of diseased southern catfish with typical septicemia symptom,and was named SCL1.The challenge experiments were carried out with healthy juvenile southern catfish by means of injection with live SCL1 at the concentration of 1.0×109 CFU/mL.All individuals of the catfish injected with SCL1 died in a week,and the symptom of the challenged fish was similar to those of the naturally diseased fish,and the LD 50 of SCL1 was calculated as 2.94×106 CFU/mL in the 22 g body weight southern catfish,while the catfish injected with 0.65% sterile solution in control group had no signs in 7 d post challenge.Therefore,SCL1 was the pathogenic bacterium strain,which was gram negative,rod-shaped,and the same as Aeromonas hydrophila in physiological and biochemical indexes except for H2S production,and was further proved to be A.hydrophila by means of its 16S rDNA sequence,which was 99.5% identical with A.hydrophila.SCL1 and was sensitive to oxytetracycline,streptomycin,ofloxacin,norfloxacin,kanamycin,and gentamycin,but resistant to penicillin sodium,midecamycin,roxithromycin,trimethoprim,and acetylspiramycin.This paper will be helpful to disease control and health management during Southern catfish farming.
出处
《中国水产科学》
CAS
CSCD
北大核心
2011年第2期360-370,共11页
Journal of Fishery Sciences of China
基金
重庆市重大科技攻关项目(CSTC,2005AB1009)
三峡库区生态环境教育部重点实验室基金资助项目
重庆市科技攻关计划项目(CSTC,2010AC1116)
