Abstract：The haemorrhagic septicaemia of domestic frog Quasipaa spinosa was rarely reported. We used conventional bacteriological methods and pathological observations to identify the pathogen and reveal the pathological damage after infection. A gram negative pathogenic bacterium was isolated from liver and ascitic fluid of the diseased frog. Regression infection proved this strain, which had LD50 of 1.59×106 cfu/g, was the pathogenic bacterium. According to result of biochemical characteristics test, phylogenetic analysis of 16S rDNA and gyrB gene sequences, this strain was identified as a species of Aeromonas hydrophila. Drug susceptibility showed that the strain was sensitive to enrofloxacin, tetracycline, and florfenicol, and resistance to cefalexin, penicillin and sulfasomizole. The histopathological observation showed obvious damage in spleen with white pulp district decreased and congestion, bleeding and broken fiber in red pulp. The epicardium showed extremely swollen with numerous neutrophils, plasma cells, and monocytes in pericardial cavity. The renal tubular epithelial cell showed hyaline degeneration with monocytes and neutrophilic granulocytes infiltration in the renal interstitial district. The hepatic cells were swollen with focal necrosis, while the neurocytes were degeneration obviously in brain tissue. Transmission electron microscope observation of spleen showed the transformation process for reticular cells to melano-macrophages and necrosis of cells and fiber, while the bacterium was digested in lysosome of macrophages. It was concluded that A. hydrophila was identified as the pathogen causing the symptoms of septicemia. The finding provided theoretical basis for the prevention and treatment of the disease.
任思宇, 吴春艳, 汪开毓, 王雯慧, 刘震坤, 杨延辉. 棘胸蛙出血性败血症的病原菌分离鉴定与病理学研究[J]. 水产科学, 2023, 42(1): 102-112.
REN Siyu, WU Chunyan, WANG Kaiyu, WANG Wenhui, LIU Zhenkun, YANG Yanhui. Isolation and Identification of Pathogenic Bacterium and Pathology of Haemorrhagic Septicaemia of Domestic Frog Quasipaa spinosa. Fisheries Science, 2023, 42(1): 102-112.
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2023, Vol. 42 
