Isolation and identification of a bacterial pathogen from Chu's croaker Nibea coibor

The usual occurrence of the diseases,which results in high mortality of adult Chu's croaker(Nibea coibor),have a negative effect on the development of high density croaker mariculture.In the present study,the pathogenic bacteria were isolated from the head of the diseased croaker of Nanao isoland,Shantou,China.A dominant green isolate(named KLg) was retrieved from the croaker.KLg was proved to be the pathogen of the diseased croaker by artificial infection and the drug sensitivity test of KLg showed that the pathogen was sensitive to 7 antibiotics such as cefoerrazone,erythromycin,ceftriaxone,cefazolin,ceftazidine,cefuroxime and piperacillin.The strain was further confirmed to be affiliated with Vibrio harveyi after gram stain,biochemical test and phylogenetic analysis and reconfirmed by 16S rDNA gene sequence and phylogenetic analysis.To our knowledge,this is the first report that V.harveyi was found to be the pathogen of cultured Chu's croaker in southern China.The results here would lay a basis on further disease prevention and remediation of Chu's croaker N.coibor in future.