华鲮烂尾病病原的分离鉴定及药敏分析

Identification and drug sensitivity test of pathogen for tail-rot disease of the fish,Sinilabeo rendahli

从患有烂尾病的华鲮(Sinilabeo rendahli)体内分离到两个优势菌株(编号:BB090516C-1和BB090516C-2),对分离菌株形态特征、主要理化特性等生物学性状鉴定后测定其16S rRNA序列并构建系统发育树,同时采用K-B琼脂扩散法进行药敏实验。结果显示:经人工感染试验,证实分离菌对华鲮有较强的致病性,该菌为革兰氏阴性、兼性厌氧发酵型短杆菌。经形态特征、培养特性和生理生化反应等指标分析鉴定结果显示该菌为维隆气单胞菌温和生物型(Aerom onas veronii biovar sobria)。用16S rRNA基因序列比对结果显示分离菌株与维隆气单胞菌的同源性高达99%,系统进化树中与维隆气单胞菌自然聚为一支,表明该菌为维隆气单胞菌温和生物型。用22种抗菌类药物进行药敏实验发现,该菌对头孢曲松、硫酸庆大霉素等9种抗菌类药物高度敏感,对新霉素等6种药物中敏,对氨苄青霉素等7种药物耐药。

Two dominant virulent strains（No.：BB090516C-1 and BB090516C-2） were isolated from Sinilabeo rendahli suffered from tail-rot disease.In order to indentify the strains,their physiological and biochemical characteristics of strains were determined.Then,the gene fragment of 16S rRNA of strains were amplified and sequenced,and phylogenetic trees were constructed.Their drug sensitivity test was performed using K-B agar diffusion method.The results showed that the strains were a type of brevibacterium with Gram-negative,anaerobic fermentation.All tests including morphological,cultured,physiological and biochemical characteristics suggested that the strains matched to Aeromonas veronii biovar sobria.Through phylogenetic tree analysis by 16S rRNA gene part sequence,the results indicated that the homology of the strains is 99% compared with A.veronii and they naturally clustered into the same branch.As a result,we first isolated and identified the infective bacterium strain were A.veronii biovar sobria.After drug sensitivity test to isolated strains with twenty antibiotics,it was found that the strains were highly sensitive to nine antibiotics（Ceftriaxone and Gentamycin Sulfate etc.）,moderately sensitive to six antibiotics（Neomycin etc.） and not sensitive to the rest seven（Ampicillin etc.）.