Isolation,identification and drug susceptibility test of pathogenic Edwardsiella tarda in Siniperca chuatsi

ObjectiveDeath causes of Siniperca chuatsi were studied,isolation and identification of pathogenic bac-teria and analysis of drug susceptibility were conducted to provide reference for effective prevention and treatment to Ed-wardsiella tarda disease in aquaculture.MethodDominant strain was isolated from liver tissue of ill S.chuatsi.Pathoge-nicity of the strain was determined by recursive infection experiment.The strain was identified by using bacteria physio-logical and biochemical analysis and 16S rDNA sequence analysis.K-B paper disk diffusion was applied to test its drug susceptibility.ResultIsolated strain FS170808 had certain pathogenicity and could lead to morbidity and death of healthy S.chuatsi.Its median lethal dose was 9.5×105CFU/mL.The strain FS170808 was identified as E.tarda through physiologi-cal and biochemical identification and 16S rDNA sequence analysis.The strain was highly susceptible to 17 kinds of drugs including ampicillin,cefatriaxone,cefuroxime,gentamicin,kanamycin,ofloxacin,tetracycline,doxycycline and the others,intermediately susceptible to cephalexin,cefradine,ceftazidine,neomycin,polymyxin B,and resistant to oxacillin, selectrin,aboren,and vancomycin.ConclusionE.tarda can lead to the morbidity and death of S.chuatsi.The highly susceptible drugs such as ampicillin,cefatriaxone,cefuroxime and gentamicin can be used for prevention and treatment in aquaculture.