Abstract：A strain of Bacterium (designed as 1214) was isolated and identified from the visceral of diseased tropical ornamental fish giant gourami (Osphronemus gorami) reared in Tianjin .The strain 1214 was found to be Gram-positive ,branching ,bead-like or long ,slender ,and filamentous rods in shapes .The infection experiments indicated that the isolated bacterium was pathogen responsible for the mortality .The traditional physiological and biochemical methods showed that most of the phenotypes of strain 1214 were similar to Nocardia ,and phylogeny analysis with 16S rDNA showed that the strain 1214 was branched into the same cluster as that of other species of Nocardia ,and had a higher identity with N .seriolae JCM 3360T (99 .9% ) .Based on the symptom of diseased fish and the grow th characteristics ,morphological , physiological , biochemical properties and phylogenetic analysis , the filamentous rod bacterium was identified as N . seriolea .Antimicrobial susceptibility assay revealed that this strain was susceptible to florfenicol ,streptomycin ,erythromycin ,doxycycline and azithromycin ,but high resistant to sulphamethoxazole and penicillin .
