Molecular epidemiology studies on aeromonas hydrophila strains isolated from fresh water fish in liaoning province | 辽宁地区养殖淡水鱼感染嗜水气单胞菌的流行病学调查

Chinese. 通过RS选择性培养基和针对16S rDNA与气溶素基因的双重PCR检测技术，对采集于辽宁省不同地区、不同鱼类、不同症状病鱼感染的嗜水气单胞菌进行了系统的流行病学调查，并对致病性嗜水气单胞菌进行了毒力验证试验及对抗菌药物的敏感性试验。结果发现，51株临床样本中有26株分离菌扩增得到685 bp大小的目的片段，证明为嗜水气单胞菌，占分离细菌总数的50.98%，占绝对的优势，其中以出血症状为主的病鱼分离的菌占23.99%，以肠炎为主症状的病鱼分离菌占17.99%，以烂鳃症状为主病鱼分离菌占9%。26株嗜水气单胞菌中有17株同时扩增出252 bp大小的气溶素基因(aerA)，表明这17株分离菌为致病性嗜水气单胞菌。人工感染试验结果表明，致病性嗜水气单胞菌均有毒力且毒力大小差异明显。药敏实验结果显示，嗜水气单胞菌不同分离株对抗生素的敏感性差异很大，对先锋V耐药率高达90%，对新生霉素、红霉素、利福平、四环素耐药率也相对较高，分别为56.2%，42.7%，37.5%，31.1%，而对氟哌酸、链霉素、庆大霉素则较敏感。该结果对建立片区病原库，揭示辽宁地区淡水养殖鱼类感染的嗜水气单胞菌的地理分布、毒力大小、耐药性差异，进而弄清嗜水气单胞菌的表型、基因型差异具有重要理论参考意义。

English. In this paper, RS selective medium and a dual PCR were used to amplify the 16S rDNA gene and aerolysin gene of aeromonas hydrophila isolated from fresh water fish in Liaoning Province. This is a relatively large scale and detailed epidemiological investigation in Liaoning Province. Besides, susceptibility testing and virulence verification test were carried out in virulent aeromonas hydrophila strains. The results showed that there were 26 isolates bacteria which obtained 685 bp fragment (the 16S rDNA gene) among the 51 collected strains, which proved to be aeromonas hydrophila. The percentage was 50.98%. Among them, 23.99% were isolated from diseased fish with main symptom of hemorrhagic, 17.99% with main symptom of enteritis, and 9% gillrot. Besides, 17 of them were amplified successfully the aerA gene (252 bp), suggesting they were pathogenic. Through the artificial infection and drug sensitive test, It was found that there were significant differences among 26 aeromonas hydrophila strains in virulence and drug resistance. Up to 90% of these strains were resist to pioneer V, and they also showed a relatively high resistant rate to novobiocin、erythromycin、rifampin and tetracycline, namely 56.2%, 42.7%, 37.5% and 31.1%. However, almost all of the strains were sensitive to ofloxacin、norfloxacin and gentamicin. This study would provide significant theoretical basis for building the area pathogen library and clarifying the differences among aeromonas hydrophila strains in geographical distribution, virulence and drug resistance, and then figuring out their phenotypes and genotypes.