Isolation and identification of a pathogenic bacterium from Epinephelus septemfasciatus with exophthalmic disease

Abstract:

A pathogenic bacterial strain CB1008 was isolated from the eyes and internal organs of seven-band grouper Epinephelus septemfasciatus. It was proved to be the pathogen of the diseased seven-band grouper by artificial infection test. Morphological observations showed that it was a short-rod and Gram-negative bacterium with single polar flagella. According to API-32E system, through traditional physiological and biochemical experiments and 16S rDNA gene homology comparison of the bacterium, the results showed that the reisolated strain CB1008 was Vibrio harveyi. The test of sensitivity of strain CB1008 to 36 kinds of antibiotics revealed that the pathogen was sensitive to Chloramphenicol, Nalidixan, Tetracycline, Norfloxacin and Fleroxacin. V. harveyi is a kind of pathogenic bacterium commonly found in cultured marine finfish,but this is the first time that V. harveyi is reported as the pathogenic bacterium of seven-band grouper in China.