Identification and characterization of Aeromonas veronii and Vibrio cholerae from naturally diseased red swamp crayfish (Procambarus clarkia)

Abstract

A large number of red swamp crayfish (Procambarus clarkia) died at a crayfish breeding farm in Tianjin. Two dominant bacterial strains were isolated from the hepatopancreas of diseased crayfish and named PCG1 and PCG2, respectively. Based on phenotypic characteristics and sequence analysis of the 16S rRNA and gyrB genes, PCG1 was identified as Aeromonas veronii and PCG2 was identified as Vibrio cholerae. An artificial infection experiment showed that both PCG1 and PCG2 were pathogenic to crayfish, with PCG1 having a median lethal dose (LD50) value of 6.25 × 102 CFU/g crayfish weight, and PCG2 having a LD50 value of 1.26 × 102 CFU/g crayfish weight. Crayfish subjected to single infection with PCG1 or PCG2 and co-infection with PCG1 and PCG2 showed obvious histopathological lesions in hepatopancreas and intestines. These findings suggested that both A. veronii and V. cholerae isolates were involved the disease occurrence in the crayfish.

Keywords

• Co-infection
• Procambarus clarkia
• Pathogenicity
• Median lethal dose
• Histopathological lesions