长丝鲈“突眼病”病原菌的分离鉴定及药敏试验

Isolation,identification and drug sensitivity of pathogenic bacterial strain from exophthalmic disease in giant gourami Osphronemas goramy

从患"突眼病"长丝鲈Osphronemas goramy肾脏中分离到1株优势菌CSL1,分别以腹腔注射、划伤浸泡和直接浸泡3种方式进行人工回归感染试验。结果表明:CSL1菌株能感染长丝鲈,且毒力较强,腹腔注射0.2 m L菌液(菌浓度为1×108cfu/m L)可导致受试长丝鲈66.7%死亡,划伤浸泡感染(菌浓度为1×108cfu/m L)死亡率达100%,直接浸泡感染(菌浓度为1×108cfu/m L)无死亡,被感染长丝鲈出现与自然感染相同的症状;对菌株CSL1进行形态特征观察和主要理化特性分析,初步鉴定为豚鼠气单胞菌Aeromonas caviae;进一步选用16S rRNA对该菌进行分子鉴定,将序列结果进行Blast分析并构建进化树,结果显示,16S rRNA基因与Gen Bank上登录的豚鼠气单胞菌的相应序列具有很高的同源性,进化树聚为一支;综合生理生化与分子鉴定结果,判定所分离的菌株为豚鼠气单胞菌;药敏试验显示,该菌株对左氟沙星、诺氟沙星、恩诺沙星、氧氟沙星、庆大霉素、卡那霉素、妥布霉素、吡哌酸8种药物高度敏感,对阿齐霉素、新霉素和强力霉素3种药物中度敏感,对新生霉素、萘啶酸、氨卞青霉素、青霉素、阿莫西林、甲氧卞啶、链霉素、复方新诺明8种药物具有耐药性。研究表明,长丝鲈"突眼病"的病原菌为豚鼠气单胞菌,其药敏结果可为防治该病提供用药参考,庆大霉素是治疗由豚鼠气单胞菌引起的各种养殖鱼类相关疾病的普适药物。

A dominant bacterium CSL1 was isolated from kidney of giant gourami Osphronemas goramy with exophthalmic disease,and artificial infection,morphological and physiological,and chemical experiments were carried out by intraperitoneal injection and immersion. The intraperitoneal injection of the bacterium（ 0. 2 mL of bacterium,1 ×10^8cfu / mL） showed 66. 7% mortality in the tested giant gourami,immersion of the injured fish with the bacterium（ 1 ×10^8cfu / mL） led to 100% mortality,and 0 mortality,and the same symptoms as the naturally infected giant gourami were found in the immersion of the fish with the bacterium（ 1 ×10^8cfu / mL）. The bacterial morphology,physiology and biochemistry assays revealed that the isolated bacterium was preliminarily determined to be Aeromonas caviae. The 16 S rRNA gene was cloned,sequenced and analyzed in the bacterium by a molecular method.Blast and phylogenetic tree showed that 16 S rRNA gene shared high similarity with its counterpart of A. caviae found in Gen Bank,indicating that the bacterium isolated was a strain of A. caviae. The drug sensitivity test showed that the isolated bacterium was highly sensitive to eight kinds of antibiotics including levofloxacin,norfloxacin,enrofloxacin,ofloxacin,gentamycin,namycin,tobramycin,and pipemidic acid,intermediate sensitive to azithromycin,neomycina,and doxycycline,and resistant to eight kinds of antibiotics including novobiocin,nalidixin,ampicillin,penicillin,amoxicillin,trimethoprim,streptomycin,and sulfamethoxazole. The findings indicated that the pathogenic bacterium of exophthalmic disease in giant gourami was A. caviae,and provided reference to preventing and curing the disease,gentamicin being a reference drug for treating the cultured fish related diseases caused by A. caviae.