鲢鳙鱼源致病性嗜水气单胞菌的分离、鉴定

Islation and identification of pathogenic Aeromonas hydrophila from Hypophthalmichthys molitrix and Aristichthys nobilis

从江西省南城县和广东省佛山市、韶关市患细菌性败血症病鲢鱼、鳙鱼体内分离到3株优势菌,人工感染鲢后证实为该病的病原菌,此3株菌对剑尾鱼的半致死量(LD50)分别为:2.64×105、9.24×104、4.45×105CFU/g。对3株病原菌进行形态特征、ATB细菌鉴定仪生理生化特性鉴定结果符合嗜水气单胞菌的特征;为进一步确定病原菌分类地位,对其16SrRNA序列扩增测序,并与相关细菌16SrRNA序列比对,构建系统发育树,在系统发育树中与嗜水气单胞菌聚类为一支。Aero气溶素基因PCR扩增出209bp条带,检测结果进一步表明此3株菌为含有毒力基因的致病性嗜水气单胞菌。

Three pathogenic bacterial strains were isolated from Hypophthalmichthys molitrix and Aristichthys nobilis from Nan Cheng, Jiangxi Province, Foshan City and Shaoguan City, Guangdong Province. They were proved to be the pathogen of the Hemorrhagic septicemia by the challenge test to Hypophthalmichthys molitrix. The semi-lethal LD50 to Xiphophorus were 2.64×105,9.24×104,4.45×105 CFU/g, respectively. The pathogenic bacterial strains were defined as Aeromonas hydrophila by the morphology, biochemical characterization and automatic ATB expression.In order to investigate the phylogenetic position of these pathogen, their 16S rRNA sequences were sequenced and compared with interrelated sequences in databases. Phylogenetic tree based on 16S rRNA genes showed that these strains clustered together with Aeromonas hydrophila. The 209 bp fraction of the aerolysin gene was amplified by the polymerase chain reaction. It was further indicated that they were pathogenic Aeromonas hydrophila containing toxic gene.