Molecular diagnosis of pathogenic Aeromonas hydrophila in Cyprinus carpio ulcers

A total of 150 carp fish were collected from Grdarasha Farm (8 kilometers from Erbil-Iraq) and examined for the presence of pathogenic Aeromonas hydrophila on their skin ulcers, this bacterium secretes a toxin protein called aerolysin which is a virulence factor and has a role in diarrhoeal diseases, deep wound infections and hemorrhagic septicemia. The present study aimed to determine the presence of A. hydrophila in common carp (Cyprinus carpio). For this purpose samples were collected from fish ulcer by swap and incubated at 37°C in blood agar to determine the shape and morphology of colonies, and then the colonies were examined by gram stain test for microscopic examination, finally molecular diagnosis was conducted for aerolysin gene with primer design and PCR. According to the diagnosis methods results were different; PCR diagnosis confirmed that only 68 skin lesions were caused by A. hydrophila, no visceral lesion was caused by A. hydrophila and this bacterium hardly ever seen in the skin surrounding mouth as only 2 lesions surrounding mouth had A. hydrophila in PCR diagnosis.