草鱼源鲁氏耶尔森菌的分离鉴定及药敏试验

Isolation,Identification and Antibiotic Sensitivity of Yersinia Ruckeri from Infected Grass Carp(Ctenopharyngodon Idellus)

为查明临沂蒙阴县某草鱼养殖场出现草鱼暴发性死亡的病因,从患病草鱼肝脾肾混合组织中分离纯化菌株,通过形态学观察、16S rRNA基因序列及其系统发育分析,确定其分类地位,利用药敏纸片扩散法检测其耐药特性。结果表明,分离的菌株是一种短杆状革兰阴性菌,在LB平板上形成表面光滑、边缘整齐、不透明的圆形乳白色菌落;基于16S rRNA基因序列构建系统发育树显示,该菌株与鲁氏耶尔森菌(Yersinia ruckeri)聚在同一分支,序列同源性高达100%;在1%氯化钠(NaCl)胰胨水、3%NaCl胰胨水、鸟氨酸脱羧酶、赖氨酸脱羧酶、MR-VP、β-半乳糖苷酶、甘露糖、甘露醇等8项试验中,结果呈阳性,与鲁氏耶尔森菌特征相近,确定分离株为鲁氏耶尔森菌。该菌株具有多重耐药性,对万古霉素、麦迪霉素、头孢唑啉、红霉素等6种药物耐受;对环丙沙星、头孢曲松、诺氟沙星、四环素等14种药物敏感。

To investigate the cause of the disease outbreak of Grass carp(Ctenopharyngodon idellus)in Mengyin county,Linyi city,Shandong province,the bacteria were isolated from the liver,spleen and kidney tissues of infected fish,and identified by morphological characters,physiological and biochemical characteristics,phylogenetic analysis of 16S rRNA gene.Then,the drug sensitivity of the isolated bacteria was detected by the the K-B disk diffusion method.The results showed that the strain was a short rod-shaped,gram-negative bacterium,which formed the white and round colony with the smooth edge and moist surface when cultured on the LB agar plate.Phylogenetic tree based on 16S rRNA gene showed that the strain had the closest relationship with Yersinia ruckeri,which had the similarities of 100%.Physiological and biochemical characteristics showed the strain was positive in 8 experiments including 1%NaCl tryptone water,3%NaCl tryptone water,ornithine decarboxylase,lysine decarboxylase,MR-VP,β-galactosidase,mannose and mannitol,which were similar to the characteristics of Y.ruckeri.The results demonstrated that the isolate was identified as Y.ruckeri.Antibiotics susceptibility test showed that the strain had multiple drug resistance,which was resistant to six drugs such as vancomycin,medemycin,cefazolin and erythromycin.It was also sensitive to 14 drugs such as ciprofloxacin,ceftriaxone,norfloxacin and tetracycline.