鳜致病性类志贺邻单胞菌的分离鉴定及耐药性分析

Identification and Drug Sensitivity Analysis of Pathogenic Plesiomonas shigelloides Isolated from Diseased Mandarin Fish Siniperca chuatsi

2019年江苏扬州某养殖场鳜出现大量死亡,临床症状表现为体表溃疡、鳃丝腐烂等,解剖发现肝脏出血。为查明鳜死亡病因,自濒死鳜分离到优势生长细菌,通过形态观察、理化特性测定及16S rRNA基因同源性分析进行分离菌的种属鉴定,同时通过人工感染试验、毒力基因检测确定其致病性,并通过纸片扩散法进行耐药性分析。结果表明:引起鳜大量死亡的病原菌株SN1为类志贺邻单胞菌,其对鳜的半数致死密度为1.05×10^(5)cfu/mL;类志贺邻单胞菌SN1携带astA、astB、astD、astE、actP、aphA等6个毒力相关基因;类志贺邻单胞菌SN1对青霉素G和克林霉素2种药物耐药,对哌拉西林、苯唑西林和麦迪霉素等6种药物中介,对恩诺沙星、硫酸新霉素、盐酸多西环素、氟苯尼考等26种药物敏感。本试验结果可为类志贺邻单胞菌引起鳜细菌性疾病的防治提供理论依据。

Outbreaks of mass mortalities occurred in mandarin fish Siniperca chuatsi farms in Yangzhou City, Jiangsu Province of China in 2019. The diseased fish had clinical symptoms of haemorrhaging on surface, gills rotting, and the presence of ascitic fluid in the abdominal cavity, enlarged gallbladder and hemorrhagic liver. The bacterial isolates from the diseased fish exhibited the same phenotypic traits and biochemical characteristics, and were identified as Plesiomonas shigelloides. In challenge test, the mandarin fish infected with the representative P. shigelloides SN1 developed similar pathological signs to the naturally diseased fish, and the LD50value of the strain SN1 to S. chuatsi was 1.05×10^(5) cfu/mL. Detection of virulence-associated genes by PCR indicated that P. shigelloides SN1 was positive for astA, astB, astD, astE, actP and aphA. According to the antibiotic resistant assay, P. shigelloides SN1 was sensitive to ampicillin, erythromycin and cephalosporins, and resistant to penicillin G and clindamycin. These findings will provide theoretical support for prevention and control of the diseases caused by P. shigelloides in mandarin fish.