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2011年8月江苏常州市武进区前黄镇某养殖场养殖的青鱼出现大量死亡,症状主要表现为病鱼口腔、头部、眼眶、鳃盖边缘、鳍条基部及鱼体尾柄处充血,肛门红肿。解剖后,可见肠道内无食物,并充血发红,腹腔内有的有淡黄色积液,肝胰脏呈紫红色、胆囊肿大。从患病青鱼肝脏、血液中分离到大量优势生长的细菌。人工感染试验证实分离菌(WJ110801-1)对健康青鱼具有很强的致病性。对分离菌进行了形态特征、理化特性等表型生物学特征检验、毒力因子检测、胞外酶分析及药敏试验,同时应用分子生物学方法测定了代表菌株的16S rRNA基因序列。结果显示,病原菌进化树与嗜水气单胞菌同源性最高,在99%以上;结合分离菌的表型及分子生物学分析,判定该菌为气单胞菌属(Aeromonas)的嗜水气单胞菌(A.hydrophila)。气溶素Aer和不耐热性细胞肠毒素alt是嗜水气单胞菌主要的毒力相关因子,利用设计的两对特异性引物对进行Aer和alt基因的PCR扩增,分离菌可以扩增出大小分别为280 bp的和250 bp的基因片段,表明本次分离的病原嗜水气单胞菌具有气溶素和细胞肠毒素毒力因子;胞外酶分析显示,分离菌具有淀粉酶、DNA酶、脲酶、明胶酶活性。分离菌进行药敏试验结果表明,供试37种抗生素中,氨曲南、氟苯尼考、庆大霉素等12种抗生素抑菌效果显著。文章报道了病原嗜水气单胞菌引起常州青鱼大量死亡,并针对病原做了详细的研究,对青鱼的疾病防控和健康养殖具有重要的参考意义。
In August 2011, a large number of herring breed blackhead carp farmed in a former farm in Wujin District, Changzhou City, Jiangsu Province. The symptoms mainly manifested as congestion of the oral cavity, head, orbit, edge of operculum, Anal swelling. Anatomy, we can see no food in the intestine, and congestion and redness, some pale yellow fluid within the abdominal cavity, liver and pancreas was purple, gallbladder enlargement. From diseased melanogaster liver, the blood of bacteria isolated a large number of dominant growth. Artificial infection test confirmed that isolates (WJ110801-1) has a strong pathogenicity to healthy herring. The isolates were characterized by morphological characteristics, physicochemical properties and other phenotypic biological characteristics, virulence factor detection, extracellular enzyme analysis and drug susceptibility testing. At the same time, the 16S rRNA gene sequences of representative strains were determined by molecular biology method. The results showed that the phytopathogenic tree had the highest homology with Aeromonas hydrophila, more than 99%. According to the phenotype and molecular biological analysis of the isolates, it was determined that the strain was Aeromonas hydrophobia A. hydrophila. Aerosols Aer and heat-labile cytotoxin alt are the major virulence-related factors of Aeromonas hydrophila. Two pairs of specific primer pairs were designed for PCR amplification of Aer and alt genes. Isolates could be expanded The gene fragments of 280 bp and 250 bp were amplified respectively, which indicated that the isolated pathogenic Aeromonas hydrophila had aerosol and cytotoxin. Extracellular enzyme analysis showed that the isolates had amylase , DNase, urease, gelatinase activity. The antibiotic susceptibility test of the isolates showed that the antibacterial effect of 12 antibiotics such as aztreonam, florfenicol and gentamycin were significant among the 37 antibiotics tested. The article reported that the pathogen Aeromonas hydrophila caused a large number of Changzhou herring died, and made a detailed study of the pathogen, the disease prevention and control of herring and healthy culture has an important reference value.