Aeromonas hydrophila was isolated from different local sources includes fresh fish, water, and lake of fish farm in Baghdad governorate, and identified according to their morphological and cultural characteristics and biochemical tests. Virulence factors produced by A. hydrophila isolates were detected to select the more virulent isolate. Results showed that these isolates have the hemolytic activity, slime production and with high ability in protease production. Antibiotic susceptibility of the more virulent isolate was examined. Results showed that A. hydrophila H4 was resistant to many antibiotics, while it was sensitive to others. Plasmid profile A. hydrophila H4 was studied by extraction of plasmid DNA and electrophoresis on agarose gel. Results showed that this isolate was harboring two small plasmids which may be responsible for the production of virulence factors and/or the antibiotics resistance. After curing of these two plasmids by using SDS (6%), it was found that cured colonies of A. hydrophila H4 was lost its ability to resist many antibiotics, while it was still having the ability to produce different virulence factors, which means that genes encoding these virulence factors are chromosomally located. Keywords: Aeromonas hydrophila, Virulence factors, DNA plasmid, curing
