一株弗氏柠檬酸杆菌的分离鉴定及致病性研究

为确定导致罗非鱼患病的原因，本试验对濒临死亡的罗非鱼进行无菌解剖，从心脏部位分离得到1株细菌，通过形态学观察、生理生化鉴定和16S rDNA分析，确定菌株为弗氏柠檬酸杆菌（Citrobacter freundii）。药敏试验结果显示，该菌株具有很强的多重耐药性，测试的20种药物中，该菌株对恩诺沙星、青霉素等13种药物具有完全耐药性，仅对头孢曲松、头孢他啶、头孢拉定、哌拉西林、舒巴坦5种药物敏感。人工感染试验结果显示，该菌对草鱼、黄颡鱼、罗非鱼、禾花鲤具有较强的致病性。本试验结果阐明了罗非鱼患病的原因，同时在养殖过程中可指导养殖户合理用药。

Isolation,Identification and Pathogenicity of a Strain of Citrobacter freundii

In order to determine the cause of disease in tilapia, the dying fish was carried out in sterile, a strain of bacterium (GXKJDX111) was isolated from the heart, through morphological observation, physiological and biochemical identification and 16S rDNA analysis, we identified the isolate as Citrobacter freundii, the results of drug sensitivity test showed that the isolate had very strong resistance, among the 20 kinds of drugs tested, the isolate was resistant to 13 kinds of drugs, including enrofloxacin, penicillin and so on, and had the sensitivity to 5 kinds of medicines, including ceftriaxone, ceftazidime, cefadroxil, piperacillin, Shubactam etc. Artificial infection showed that the bacterium had strong pathogenicity to grass carp, Pelteobagrus fulvidraco, tilapia and Procyprismerus. The result clarified the causes of the prevalence of tilapia, and could guide the farmers to use drugs reasonablely in the breeding process.