Abstract: In order to investigate the pathogenesis of abscess disease in cultured Yesso scallop Patinopectenyessoensis, dominant single colonies were selected from the lesions sited by coating culture, and the dominant strains were studied through isolation and purification, drug sensitivity test, hemolysis test, artificial infection test and histopathological examination. The results showed that a total of 12 dominant bacterial strains ( from YD-1 to YD-12) were obtained from Yesso scallop lesions. The 16S rDNA gene sequence alignment analysis showed that the 12 strains had the maximal similarity with Shewanellacolwelliana. The YD-1 strain with the maximal sequence identity(99.86%) with S.colwelliana was cultured and observed by transmission electron microscopy. It was found that the YD-1 strain was a creamy yellow colony with a diameter of 1.0 mm to 1.5 mm and was rod-shaped with one terminal flagella and negative response by Gram staining. After physiological, biochemical tests and 16S rRNA analysis, YD-1 was identified as S.colwelliana. The results of antibiotic susceptibility revealed that the YD-1 strain was highly susceptible to cefotaxime, cefoperazone, chloramphenicol and azithromycin, with α haemolytic activity at 28 ℃ and 37 ℃. The results of injection test showed that the YD-1 strain was highly pathogenic, with median lethal dose (LD50) of 2.08×106 CFU/mL. The infective symptoms included capsid atrophy and detachment, weak obturator muscle contraction, slow response to external stimulation and brown deposition on the shell edge, without pink orange pustule, which were not exactly similar to the symptoms of abscess. The finding indicated that S.colwelliana YD-1 strain was a potential pathogen of Yesso scallop and participated in the occurrence of abscess.
2022, Vol. 37 
