患病草鱼肠道病原菌的分离鉴定及毒力研究

Isolation,Identification and Virulence of Pathogenic Bacteria in Gut of Diseased Grass Carp Ctenopharyngodon idellus

自环洞庭湖区精养鱼池患病草鱼肠道中分离获得4种病原菌,进行16S rRNA基因和gyrB基因序列测定和在线比对,并对草鱼进行回归感染。随后进行4种病原菌的药敏特征、溶血活性试验,并利用PCR方法检测了6种毒力因子的携带情况。试验结果表明,病原菌分别为温和气单胞菌、异常嗜糖气单胞菌、类志贺邻单胞菌和格氏乳球菌;4种病原菌回归感染草鱼,均能使草鱼患病致死,自死亡的草鱼体内均能分离得到相应感染的病原菌;4种病原菌对多种抗生素具有耐药性,且在脱纤维绵羊血血平板上检测到了温和气单胞菌、异常嗜糖气单胞菌AaB007的溶血活性;PCR结果表明,4种病原菌携带多种毒力因子。研究结果可为环洞庭湖区草鱼精养鱼池健康养殖及病害防治提供科学依据。

Four pathogenic strains were isolated from intestine of diseased grass carp ( Ctenopharyngodon idellus ) collected from an intensive fish farming ponds in Dongting Lake area. The 16S rRNA gene sequencing,gyrB gene sequencing and BLAST analysis revealed that these four pathogenic bacterial strains were Aeromonas sobria , A. allosaccharophila , Plesiomonas shigelloide and Lactococcus garvieae . The infection tests indicated that all these four pathogenic strains were lethal to grass carp,and the corresponding pathogenic bacteria were isolated from the dead grass carp. Subsequently,we studied the drug sensitivity and hemolytic activity of these four strains,and it was approved that they carried the six toxicity genes by PCR. The results showed that the four pathogenic strains had resistance to a variety of antibiotics and many toxicity genes. The findings provide important scientific basis for healthy aquaculture of grass carp in intensive fish culture ponds in Dongting Lake area and that more attention should be paid to prevention and control of freshwater fish diseases.