乌鳢源杀鱼爱德华菌的分离鉴定及药敏特性研究

背景] 江苏省扬州市某乌鳢养殖场发生疾病，给养殖户造成了严重的经济损失。目的] 确定病因并筛选出敏感药物，为乌鳢相关疾病的防治提供参考。方法] 从患病乌鳢体内分离致病菌，并从形态、生理生化特征、16S rRNA和gyrB基因序列及特异性PCR检测等方面对分离菌株进行鉴定，同时开展人工感染试验分析其致病性，通过纸片扩散法进行药敏特性分析。结果] 从患病乌鳢体内分离获得优势菌株SHL，经形态特征、理化特性、16S rRNA和gyrB基因序列及特异性PCR检测鉴定为杀鱼爱德华菌。进一步人工感染试验证实其对乌鳢有较强的致病性，LD₅₀为1.6×10⁵ CFU/g，发病症状与自然发病症状相似。药敏试验结果显示，该菌株对青霉素、氯霉素、四环素等28种抗菌药物高度敏感，对红霉素中度敏感，对苯唑西啉、克拉霉素、万古霉素等6种药物耐药。结论] 引起江苏省扬州市某养殖场的乌鳢体表溃烂及死亡的病原菌为杀鱼爱德华菌，这是我国首次从淡水鱼类中检出致病性杀鱼爱德华菌，表明该菌的感染谱在扩大，需引起水产养殖领域的重视，在养殖过程中可根据药敏实验结果选用合适的国标渔药进行防治。

Isolation, identification and antibiotic sensitivity of Edwardsiella piscicida from Channa argus

Background] A fish disease occurred in a snakehead farm in Yangzhou, Jiangsu Province, causes great economic losses. Objective] To determine the etiology and screen out sensitive drugs for the control of snakehead-related diseases. Methods] The pathogenic bacteria were isolated from the sick snakeheads, and the isolates were identified in terms of morphology, physiological and biochemical characteristics, 16S rRNA gene and gyrB sequences and specific PCR assays, while their pathogenicity was analyzed by artificial infection tests and antimicrobial sensitivity was tested by paper diffusion method. Results] A dominant strain SHL isolated from the sick snakeheads was identified as Edwardsiella piscicida, by its morphological characteristics, physicochemical properties, 16S rRNA gene and gyrB sequences, specific PCR results, and further artificial infection tests confirmed its strong pathogenicity to snakeheads with an LD₅₀ of 1.6×10⁵ CFU/g with similar symptoms to natural disease. The drug sensitivity test results showed that the strain was highly sensitive to 28 antibacterial drugs such as penicillin, chloramphenicol and tetracycline, moderately sensitive to erythromycin, and resistant to 6 drugs such as oxacillin, clarithromycin and vancomycin. Conclusion] Edwardsiella piscicida is the pathogen causing the ulceration and death of snakeheads (Channa argus) cultured in Yangzhou, Jiangsu province. It is the first time that Edwardsiella piscicida was detected from freshwater fish in China. The results demonstrated that the infection spectrum of Edwardsiella piscicida is expanding, which needs to be paid more attention in the field of aquaculture. In aquaculture practice, we can treat the disease with the appropriate national standard fishery drugs according to the results of the drug sensitivity test.