Isolation and identification of pathogen Streptococcus iniae in diseased hybrid snakehead (Channa argus♂× Channamaculata♀)

ObjectiveThe pathogens from diseased hybrid snakehead (Channa argus♂×Channa maculata♀) in an aquafarm in Zhongshan City of Guangdong Province were isolated and identified and antibiotic sensitivity test was per-formed in order to determine the causes and provide references for preventing and controlling this disease effectively.MethodPathogenic bacteria were isolated from moribund hybrid snakehead , and they were identified through physio-logical and biochemical characteristics test and 16S rRNA sequence analysis. Furthermore , antibiotic sensitivity test was performed through Kirby-Bauer disk diffusion method. ResultTwo dominant bacterias (ZS2013711-1, ZS2013711-2) were isolated from moribund hybrid snakehead , and they were identified to be Streptococcus iniae according to their physiological and biochemical characteristics and 16S rRNA sequence analysis. The half lethal dose values for the iso-lates to healthy hybrid snakehead were 2.7 ×105 and 6.7 ×105 CFU/g, respectively. The results of antibiotic sensitivity test showed the isolates were highly sensitive to cefotaxime, cefradine, cephazolin, lincomycin, and so on. Conclu-sionHybrid snakehead is a new found host for S. iniae. In hybrid snakehead aquaculture industry , its disease resulted from S. iniae can be prevented and treated by cefotaxime, cefradine, cephazolin and lincomycin.