Isolation, Identification, and Detection, of the Virulence Factor of Vibrio cholerae in Grass Carp

Abstract

In this study, we examined the mass mortality of grass carp (Ctenopharyngodon idellus) caused by Vibrio cholerae in Jiangsu Province. We evaluated the phenotypic, morphological, physiological, biochemical, and virulence factor characteristics as well as the drug sensitivity of the CY-1 strain isolated from the liver, spleen, and kidney, of dying grass carp. The 16S rRNA gene (GenBank accession number: KF386612) was amplified and compared with sequences deposited in GenBank. A phylogenetic tree analysis showed that the isolated pathogen was V. cholerae and that it was most closely related to V. cholerae (GenBank accession number: JN555611). Artificially infected grass carp that died exhibited the same disease symptoms as those of naturally infected fish. An amplified band in the corresponding 564-bp position was detected as the virulence factor, and it was the same as that of the V. cholerae virulence factor ctxA. Drug sensitivity tests showed that V. cholerae was resistant to penicillin, tobramycin, cotrimoxazole, and amoxicillin, and was highly sensitive to cefuroxime, amikacin, tetracycline, and nitrofurantoin. These could possibly be used in the treatment of this disease. The findings of this study can be used as a reference for disease control and health management in the cultivation of C. Idellus.