The present study included the detection of A.hydrophila in some clinical cases and environmental sources in the governorate of AL-Najaf, Clinical samples and Environmental samples. The PCR method of gene (16S rRNA) was the best methods for diagnosis. The virulence factors of bacteria were detected and showed that all isolates were produced of heamolysin, protease, lipase, phospholipase, gelatinase, sidrophore, and capsule formation. They are also observed clear variation in their susceptibility to (26) antibiotics. The PCR technique was used for detection of some genes in A.hydrophila like hemolysin (hyl) and aerolysin (aerA) genes which were responsible for pathogenicity of bacteria. The current study demonstrates that the effect of some the environmental factors on enzymes production that included (hemolysin, protease, lipase and phospholipase enzymes) of A.hydrophila. The results show that the optimal production of enzymes at temperature (37ºC) and pH (7) for clinical. While (22 and 37ºC ) and pH (7 and 9), for environmental isolates. Some clinical and environmental isolates containing hemolysin gene were tested Ligated Ileal intestinal of rabbit.