大鳍鳠腹部一种感染性疾病病原菌确定及药敏研究

Isolation,Identification and Pathogenicity of a Pathogenic Bacterium from Largefin Longbarbel Catfish,Mystus macropterus Bleeker

自患头顶溃疡症的大鳍鳠内脏组织中分离出致病菌株MM-A,对该菌进行了鉴定。人工感染试验证实,MM-A菌株为大鳍鳠的病原菌,其半致死量(LD50)为5.3×107 cfu/mL。根据菌株形态学特点、生理生化指标和16SrDNA序列确定其为鲇爱德华氏菌。16SrDNA序列分析显示MM-A菌珠与鲇爱德华氏菌的亲缘关系最近,同源性达99.4%;系统进化树分析表明该菌与鲇爱德华氏菌聚为一支。14种药物敏感性试验结果显示,该菌对土霉素、链霉素、氧氟沙星和庆大霉素均敏感,对四环素等5种抗生素及中草药柯子和秦皮比较敏感。

Bacterial pathogen strain MM-A was isolated from largefin longbarbel catfish （ Mystus macropterus） , suffered from a kind of disease with typical head-ulcerative symptom . The bacterial pathogen strain MM-A was confirmed to be the causative agent of the epidemic by artificial infection test and the LD50 was about 5 .3 × 10^7 cfu/mL .According to physiological feature ,biochemical indexes and 16s rDNA sequence ,the MM-A was further proved to be Edwardsiella ictaluri .The comparison of 16S rDNA molecule in Enterobacteriaceae showed that the strain MM-A shared the highest level of similarity （99 .4% ） with that of the E .ictaluri ,and they had the same position in the molecular phylogenetic tree based on 16S rDNA sequence in Enterobacteriaceae .The drug susceptibility test revealed that the isolated strain MM-A was susceptible to oxyteracycline ,streptomicinum ,ofloxacin and other antibiotics ,lowly susceptible to tetracycline and other antibiotics and Chinese medicinal herbs including Terminalia chebula , and Fraxinus rhynchophylla .