Isolation and identification of pathogenic bacteria associated with black-mouth disease in sea urchin Strongylocentrotus intermedius
LIU Yansong, ZHANG Weijie, WANG Zhong, YIN Weijun, OU Fanjiang, TIAN Wenzhuo, LIU Lei, CHANG Yaqing*
Key Laboratory of Mariculture & Stock Enhancement in North China’s Sea, Ministry of Agriculture and Rural Affairs, Dalian Ocean University, Dalian 116023, China
Abstract: In order to probe into the pathogen of black mouth disease in sea urchin Strongylocentrotusintermedius, a dominant strain (D1) was isolated from the coelomic fluid of the sea urchin with the black mouth disease and then was artificially challenged to the healthy sea urchin to confirm the pathogenicity. The pathogenic bacteria were subjected to electron microscopic observation, gram staining, physiological and biochemical identification and 16S rRNA sequence comparison to identify its classification. The sensitivity of the strain to 30 antibiotics was also detected. The results showed that after being alleloped by D1 strain, the symptoms of the sea urchin with bulbus intermedius are the same as those of the sea urchin with black mouth disease in the natural state and the same strain was isolated in the humor of the sea urchin cavity. It was found that the bacterium was (2.10±0.31)μm × (0.68±0.08)μm (length × width) in size, with gram negative. 16S rRNA comparison showed that the bacterium was similar to Vibrioechinoideorum with as high as 99.04% of similarity. The bacterium reacted positively with sucrose, 6% sodium chloride solution, and oxidase. The physiological and biochemical test and the molecular biology identification results of 16S rRNA revealed that the pathogen was V.echinoideorum. The susceptibility test showed that the strain was sensitive to 16 antibacterial drugs such as ofloxacin, polymyxin B, compound trimoxazole, ampicillin, carboxicillin, and cefazolin and resistant to 11 antibacterial drugs including medithromycin and gentamicin. The finding indicated that V.echinoideorum was the pathogen of the black-mouth disease in sea urchin, which is not sensitive to some antibacterial drugs and has certain drug resistance.
2022, Vol. 37 
