ISSN: 0975-8585 Page No. 575 5(5) RJPBCS 2014 September - October Research Journal of Pharmaceutical, Biological and Chemical Sciences A contribution on Pseudomonas aeruginosa infection in African Catfish (Clarias gariepinus) Magdy, I.Hanna 1 , Maha A. El-Hady 2 , Hanaa A. Ahmed 3 , Saher A.Elmeadawy 4 and Amany M. Kenwy 5 1 Department of fish diseases and management, faculty of Vet. Med., Cairo University. 2 epartment of fish diseases, Animal Health Research Institute, Dokki , Giza. 3 Department of Biotechnology, Animal Health Research Institute, Dokki , Giza. 4 Department of Biochemistry, Animal Health Research Institute, Dokki , Giza. 5 Department of Hydrobiology, National Research Institute, Dokki , Giza. ABSTRACT In this study, samples from cultured Common carp (Cyprinus carpio), Nile tilapia (Oreochromis niloticus) and African catfish(Clarias gariepinus) fishes were collected from Kafr el-Sheikh, Menofya, Behira and Sharkia Governorates in Egypt for detection of Pseudomonas aeruginosa infection. Isolation and identification of Pseudomonas aeruginosa was done by traditional methods then confirmed using regular PCR technique. Pseudomonas aeruginosa gave 956 bp product size specific for 16S rDNA. The experimental inoculation of Clarias gariepinus with Pseudomonas aeruginosa was fully demonstrated. The most common clinical signs were external haemorrhage and ulcer with mortality rate 40%. Histopathological changes revealed degeneration and necrosis in all internal organs associated with hyperplesia in the wall of the blood vessels. Chronic inflammatory cell infiltration and melanomacrophage cells were detected in all fish tissues. The effect on some oxidative stress and immunological parameters of experimentally inoculated Clarias gariepinus with Pseudomonas aeruginosa were studied. Results revealed that there were significant increase in lipid peroxidation product (malondialdehyde) , hypoprotineamia, hypoalbuniaemia and hypoglobulinaemia. In-vitro sensitivity test of isolated Pseudomonas aeruginosa iitalosi to different chemotherapeutic agents was conducted. In conclusion, this study showed that P.aeruginosa infection is common in some common cultured freshwater fishes in Egypt. It can be diagnosed easily using PCR technique.The experimental infection of Clarias gariepinus with P.aeruginosa was associated with mortality rate 40 % , severe histopathological changes in all organs of infected fishes, immunosuppression and oxidative damage of tissues which reflect the significant economic importance of Pseudomonas aeruginosa infection in cultured fishes. Colistin sulphate, Danofloxacin, Nalidixic acid, Oxolonic acid and Oxytetracyclinen are recommended for control of Pseudomonas aeruginosa infection in cultured fishes. Keywords: Pseudomonas aeruginosa , histopathological changes, sensitivity test, oxidative stress , PCR, Clinical signs. *Corresponding author