Isolation and Identification of Septicemia Pathogen of Ictalurus Punctatus

In recent years,a communicable disease attacked Ictalurus punctatus in cage culture in Zhexi reservoir,Wuqiangxi reservoir and Fengtan reservoir Hunan province,which resulted in the mass mortality of Ictalurus punctatus.The infected fish had the symptom of exophthalmos,abdominal tympanites,the red swelling anus,abdominal hydropsy,swollen liver,spleen and kidney,and hyperemia of intestinal wall.In this study,three pathogenic strains(FB1,FB2,FB3) were isolated from intestinal wall,liver,spleen and stomach of the septicemia-infected Ictalurus punctatus.It was found that strain FB1 was pathogenic bacteria causing septicemia of Ictalurus punctatus by using artificial infection experiments.The 16S rDNA sequence of strain FB1 had a high homology with Aeromonas hydrophila.The strain FB1 was further identified as Aeromonas hydrophila by the morphological,the physiological,bio-chemical experiments.According to the identification result,FB1 is aeromonas hydrophila,FB2 and FB3 are Stenotrophomonas maltophilia.