Recently, diseases of koi carp Cyprinus carpio var. koi have resulted in the mass mortality of stock at a koi carp breeding farm in Tianjin. The diseased fish exhibited obvious symptoms including skin ulceration, hemorrhages on body surface, and abdominal and intestinal dropsy. Seven Gram-negative bacterial isolates were isolated from the liver and spleen of diseased koi carp. Based on the phenotypic characteristics and sequence analysis of the 16S rRNA and gyrB genes, four isolates were identified as Aeromonas veronii and named as KCL-1 to KCL-4; three isolates were identified as Vibrio cholerae and named as KCS-1 to KCS-3. Two isolates A. veronii KCL-1 and V. cholerae KCS-1 were representatively used for the artificial experimental infection in the koi carp. Infection with single bacterial isolate or co-infection with these two isolates showed that both A. veronii KCL-1 and V. cholerae KCS-1 were virulent for the koi carp, while the former was more virulent than the latter. Meanwhile, the fish infected with the A. veronii KCL-1 and co-infected with the two isolates exhibited similar external clinical signs and histopathological changes with the naturally diseased ones. The positive result of the fluorescence in situ hybridization proved the presence of these two isolates in the spleen and liver of the co-infected fish. These results indicated that both A. veronii and V. cholerae participated in the disease outbreaks of the koi carp.

近日，锦鲤的疾病鲤鱼变种。锦鲤导致天津锦鲤养殖场种群大量死亡。患病的鱼表现出明显的症状，包括皮肤溃疡，体表出血以及腹部和肠道的水肿。从患病锦鲤的肝脏和脾脏中分离出七个革兰氏阴性细菌分离株。根据16S rRNA和gyrB基因的表型特征和序列分析，鉴定出四个分离株为Veronii，并命名为KCL-1至KCL-4。三个分离株被鉴定为霍乱弧菌，并命名为KCS-1至KCS-3。两种分离株ver.ii KCL-1和霍乱弧菌KCS-1代表性地用于锦鲤的人工实验感染。单一细菌分离株的感染或与这两种分离株的共同感染显示，ver.ii。veronii KCL-1和霍乱弧菌KCS-1对锦鲤有毒力，而前者比后者更具毒力。同时，感染了A. veronii KCL-1并与两种分离株共同感染的鱼表现出与自然感染相似的外部临床体征和组织病理学变化。荧光原位杂交的阳性结果证明了这两种分离株在共感染鱼的脾脏和肝脏中的存在。这些结果表明，A。veronii和霍乱弧菌参与了锦鲤的疾病暴发。