Phân lập và định danh vi khuẩn phát sáng gây bệnh trên cá Ngựa đen (Hippocampus kuda)

Seahorse (Hippocampus spp.) are economically valuable species and are used in traditional medicine.  In  Vietnam,  seahorse  cultivation  has  been  recently  developed  in  some  regions namely Khanh Hoa, Ninh Thuan, Hue, Da Nang and Vung Tau. Three seahorse small-scale farms  in Khanh  Hoa  are  now  facing  problems  with  unknown  disease  occuring in  common seahorses (Hippocampus kuda Bleekers 1852). In the present study, luminous bacteria were isolated  from  a  total  of  35  Hippocampus  kuda,  which  had  ulcerations.  Physiological  and biochemical  testing  as  well  as    16S  rDNA  sequencing  confirmed  that  the  photobacterium (named TNX-X1)  was closely related to Vibrio harveyi. Infectivity studies (challenge test) were  conducted  directly  in  Hippocampus  kuda  showed  that  this  Vibrio  isolate  caused  a disease with symptoms including white changing, viscous skin and ulceration. LD50  (Lethal dose 50%) for fish with an average body weight of 1 – 2g was 5x10 6 CFUxfish-1. The isolate, in  addition,  was  resistant  to  certain  antibiotics  including  ampicillin10µg/disc  (A10), cefadroxil 30µg (CD30), amoxicilin 25µg (AMC25) and cefalexin 30µg (CL30) (in total 9 antibiotics).