Isolation, Identification And Pathological Study Of Pathogenic Bacteria Of Trionyx Sinensis

Trionyx sinensis is an important economic species for freshwater aquaculture in China.with the rapid development of high-density aquaculture and the increasing scope of breeding,various pathogens that endanger the culture of T.sinensis are also emerging,and diseases are erupted every year,causing a large number of deaths of T.sinensis.The main reason is the skin of the body surface.Infected by bacteria,the huge economic losses to the farmers have seriously restricted the healthy and sustainable development of the T.sinensis breeding industry.In this research,two pathogens were isolated from the lesions of the T.sinensis disease,the liver and the intestines,which were bred from the farm.The dominant bacteria Lb18-01and Lb18-02,and the physiological and biochemical methods to identify the two pathogens,At the same time,combined with molecular biology techniques,the 16Sr DNA sequences of the two strains were compared with the bacterial 16Sr DNA in the NCBI gene pool,and the gene sequences of the two strains were compared with the 16Sr DNA of the most homologous bacteria collected in Genbank by ClustalX and MEGA software.Homology similarity analysis,constructing a phylogenetic tree.The results showed that the molecular biological detection method was consistent with the traditional biochemical physical and chemical identification,and Lb18-01 was identified as Proteus vulgaris and Lb18-02 was caused by Elizabethkingia meningoseptica.The symptoms in the artificial infection experiment are the same as those of the T.sinensis disease in the artificial breeding process.The LD50 of Lb18-01 on healthy young T.sinensis at 48h and 96h was 1.0×10~6 CFU/g and 8.4×10~5 CFU/g,respectively.The LD50 of Lb18-02 on healthy young T.sinensis 48h and 96h were 8.2.×10~5 CFU/g and 6.3×10~5CFU/g.Drug sensitivity test results showed.Both pathogenic bacteria showed resistance to20 kinds of drugs such as penicillin,tetracycline and ampicillin.Comparing the diseased and healthy T.sinensis tissue sections,the results showed that various internal organs such as liver,spleen,kidney and intestine had different degrees of lesions.Comparative analysis of serum biochemical indicators of sick and healthy T.sinensis,It was found that serum albumin,globulin,total protein content,high density lipoprotein,aspartate aminotransferase,catalase and reduced glutathione were lower than those in healthy sputum.The activities of serum glucose,low density lipoprotein,serum total cholesterol,alanine aminotransferase,glutathione peroxidase,total superoxide dismutase,alkaline phosphatase,acid phosphatase were significantly lower than healthy sputum.The diseased urea nitrogen,cereal enzymes.the ratio of alanine to the enzyme was higher than the health,and the content of creatinine was significantly higher than the health.This thesis takes T.sinensis in a certain area of Hunan as the research object.Isolation and pathogenic bacteria,histopathological study,and blood biochemical indicators.Aim to provide a theoretical basis for the diagnosis and prevention of T.sinensis disease,providing information for production practice.