Isolation,identification and antibiotic susceptibility analysis of Shewanella xiamenensis from Cyprinus carpio var.Koi

ObjectiveThe cause of death for Cyprinus carpio var.Koi and antibiotic susceptibility of its pathogens were clarified to provide reference for effective prevention and control of this disease in breeding.MethodThe pathogenic bacteria were isolated from the diseased fish using the conventional method.The species of the isolated strain was identi-fied according to the morphological observation,physiological and biochemical characteristics identification and 16S rD-NA sequences analysis.Then,an artificial infection experiment was carried out to identify its pathogenicity.Kirby-Bauer method was used for antibiotic susceptibility test.ResultTaking the morphological characteristics,physiological and biochemical characteristics and 16S rDNA sequences analysis into consideration,the bacterial strain isolated was finally identified as Shewanella xiamenensis.Results of artificial infection experiment showed that the isolated S.xiamenensis strain from liver of diseased fish was highly virulent.Its median lethal dosage(LD50)for the zebra fish was calculated as 2.30×104CFU/g.The results of antibiotic susceptibility test showed that the S.xiamenensis was highly susceptible to 14 drugs such as amoxicillin,meropenem,imipenem,gentamicin,neomycin,kanamycin,cefoperazone,cefixime,cefo-taxime,azithromycin,erythromycin,clindamycin,chloramphenicol,and florfenicol.While it was resistant to ampicil-lin,levofloxacin,norfloxacin,enrofloxacin,rifampicin,streptomycin,enoxacin,sulfisoxazole and trimethoprim.Con-clusionS.xiamenensis can infect C.carpio and cause the death of it.The virulence of S.xiamenensis is strong.Some anti-biotics such as amoxicillin,meropenem,imipenem,gentamicin,neomycin,kanamycin,cefoperazone,cefixime,cefo-taxime and azithromycin can be used for prevention and treatment of this disease in breeding.