关键词: RS选择性培养基;16S rDNA基因;气溶素基因;药敏试验

Abstract:

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% gill-rot. 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.

Key words: RS selective medium, 16S rDNA gene, Aerolysin gene; , susceptibility testing