The evaluation of virulence genes in Aeromonas hydrophila isolated from crayfish Astacus Leptodactylus

Infectious diseases are major economic losses in fish production facilities. Aeromonas hydrophila is considered as an important pathogen causing primary infection in wounds or the secondary problem following stress raised from temperature changes, handling, or poor water quality. This study was aimed to isolate A. hydrophila from crayfish Astacus Leptodactylus and to determine its virulence genes. Ten infected crayfish were investigated in this descriptive study. Samples were cultivated on Brain Heart Infusion (BHI) Agar medium. Bacterial identification was performed using both biochemical and molecular tests. Also, the presence of three virulence genes (lipase, elastase, and aerolysin) was investigated in the isolates. Two A. hydrophila strains were isolated from 10 infected crayfish with symptoms including black plaque, abscess, soft shell, corrosion appendages, and lethargy. One of the isolated strains had lipase and elastase genes, and the other one contained lipase, elastase, and aerolysin virulence genes. Our results showed the presence of different virulence genes in different A. hydrophila strains isolated from infected crayfish. Further studies are required to clarify the role of these genes in pathogenicity and virulence-related symptoms in the aquatic species.