First case of non-O1/O139 Vibrio cholerae infection in the pink-tailed chalceus Chalceus macrolepidotus in China.

A pathogen was isolated from diseased pink-tailed chalceus Chalceus macrolepidotus during a high-mortality outbreak in a freshwater culture farm in Liaoyang, China. The diseased fish were characterized by disoriented behaviors, exophthalmos, and redness and swelling of the top of the head. A Gram-negative, pure strain of bacteria (CM0428) was isolated from the brain, kidney, and liver. The isolate was identified as Vibrio cholerae based on ompW gene amplification and 16S rRNA and gyrB gene sequence analysis. Serogroup testing indicated that CM0428 was a non-O1/O139 strain of V. cholerae. The challenge test showed that CM0428 exhibited strong virulence to pink-tailed chalceus, and hlyA and toxR virulence-related genes were detected. The isolate was sensitive to multi-class antibiotics, but resistant to tetracycline. Histological examination revealed that V. cholerae CM0428 infection caused multiple organ and tissue lesions, and typical pathological features were cell degeneration and necrosis.