Isolation, Identification and Characterization of Aeromonas hydrophila from Hemorrhagic Grass carp
草鱼出血病混合感染的嗜水气单胞菌的分离、鉴定与理化特性

Two strains of infectious bacteria and a GCRV-like virus were isolated from grass carp which seemed to be infected by both virus and bacteria in Guangdong and Fujian provinces. CIK cells were inoculated with tissue fluid filtrated from the diseased fish. GCRV-like virus particles and virus inclusion body were observed in the cytoplasm of the infected cells under electron microscope. Artificial infection experiments showed that healthy grass carp died after infected with both the bacteria strains and virus-infected cell culture supernatant. Bacteria morphology, characteristics, physiology and biochemistry assays were used to identify the isolated bacteria. The characteristics of the two strains isolated were in accordance with those of Aeromonas hydrophila. PCR was performed to identify the bacteria. Both 16S rRNA gene and gryB gene of the two strains possessed high similarity with those of A. hydrophila registered in GenBank. AerA and ahpA genes could be amplified in both strains which indicated that both of them possessed strong pathogenicity. The two strains were therefore identified to be virulent strains of A. hydrophila. The diseased grass carp analyzed was supposed to be mixed infected by both A. hydrophila and virus.