Analysis on the Virulence Genes and Drug Resistance of Aeromonas veronii in Ctenopharyngodon idellus

In order to understand the epidemic season of Aeromonas veronii and the virulence gene carrying situation of Aeromonas veronii in different periods and its prevention and control methods during the aquaculture process of Ctenopharyngodon idellus, seven strains of pathogenic bacteria were isolated from the tissues of diseased Ctenopharyngodon idellus, such as liver, kidney, and spleen in the aquaculture farm of Shunchang County, Fujian Province. The isolated strains were analyzed by using the bacterial isolation & culture, gram staining microscopic examination, biochemical identification, virulence genes, drug sensitivity test, 16S rRNA and gyrB gene sequencing. The results showed that the seven pathogenic bacteria isolated from Ctenopharyngodon idellus showed the round yellowish bacterial colony with smooth moist surface and neat edge in the culture medium. β-hemolysis was observed around the colony, and the gram staining microscopic examination showed the negative brevibacterium. Through the 16S rRNA and gyrB gene sequencing analysis combined with the biochemical identification and mass spectrum identification, the identification results were all Aeromonas veronii. The PCR result of the eight kinds of virulence genes showed that all the isolated strains all carried 6 kinds of virulence genes including Lip, Act, aerA, Alt, Exu and Fla. The results of drug sensitivity test showed that all the strains had the same sensitivity to the eight kinds of antibiotics, and were relatively sensitive to the seven kinds of antibiotics, such as oxytetracycline hydrochloride, thiamphenicol, flufenicol, sulfamethoxazole, sulfadimethoxine, josamycin and enrofloxacin, while were relatively resistant to the six kinds of antibiotics, such as ampicillin sodium, neomycin sulfate, sulfadiazine, sulfamonomethoxine, doxycycline and erythromycin.