Isolated And Identification Of Pathogenic Bacteria And Pathomorphology Of Ulcer Disease In Silurus Meriordinalis Chen

A communicable diseases of Silurus meriordinalis Chen was outbreak in Luzhou,Qionglai,Xinjing,Dayi,Meishan,Hechuan of Chongqing et. in 2005, which characteristic was ulcerated in body surface of the fish.This diseaes was highly morbility and mortality. The pathogeny was unknown, while the fishers were blind in medication,the pathogenetic condition was difficult to control. It was affecting and restricting Silurus meriordinalis Chen breeding severely.Once,the confidence of culturist was destabilized. Therefore, etiological study was conducted in order to solve the disease problems and maintain the sustainable development for the industry.Isolated a bacteria named DKN-1 from the sick Silurus meriordinalis Chen. It was Gram negative, rod bacteria, polar flagellum.. Traditinal biochemical and 16S rDNA sequence of strain show that DKN-1 was A.caviae. In the phylogenetic tree DKN-1 and A.caviae were the closest relative with 99.6% sequence similarity.In a word ,the pathogenic bacteria of Silurus meriordinalis Chen ulcer diseases was A.caviae. The pathogenic bacteria was hypersensitive to minocycline,spectinomycin and tenemycin. The MBC of benzalkonium and Glutaraldehyde were the lowest in the common disinfectants,both were 0.31 g/ml.The pathology of artificial challenge by Aeromonas caviae was studied.Theresults showed that the liver , kidney , spleen , mesentery of the infected fish were engorgement.The hindgut was thin and to be full of yellow mucus, the open ulcer in the skin.In the histopathology, the muscle, gastrointestinal tract , gill,and the fundamental organs were damaged. They were degeneration, necrosis, inflammatory cell infiltration. In the cytopathology,the organelles were damaged differently, ultramicrostructure was destroy.The mitochondrias were obviously injured,at last,the caryons were disappeared. The sick fish died by damage and functional impairment of major organ.