Pathogenic Bacteria Influencing the Common Carp (Cyprinus carpio L.) Farming in Floating Cages in Dayla Province

Bacterial infections that arise naturally in the environment of fish present a major challenge for fish ‎farming in Iraq and globally. The objective of this study was to isolate pathogenic bacteria from ‎common carp that are raised in floating cages and subsequently sold in the local market of Diyala ‎Province. The local examination involved counting 100 fish and collecting samples from them. A ‎dissection was conducted on each fish in the laboratory, isolating bacterial strains from different ‎regions including the skin, gills, liver, spleen, kidney and intestines. Bacteria were ‎identified through microscopic examinations and biochemical tests to pinpoint potential isolates, ‎subsequently confirmed using the API® 20 E system for each strain. ‎The bacteria isolated from all ‎targeted organs showed that the potential pathogenic bacteria identified include E. coli, Aeromonas ‎‎hydrophila, Pseudomonas ‎aeruginosa and Staphylococcus ‎spp.‎ In carp from this study, E. coli recorded the highest bacterial numbers in ‎the skin and spleen compared of that Pseudomonas aeruginosa and Staphylococcus spp. The ‎maximum bacterial count in fish organs is found in the skin and spleen (3.27 × 106), while the ‎minimum count is observed in the gills and kidneys (1.91 ± 0.14) ×106. The study illustrates the ‎effect of different antibiotics on the isolated bacteria. The antibiotics used include chloramphenicol ‎‎(C30), ceftazidime (KF30), cefoxitin (ZOX30), ticarcillin (TI30), oxacillin (OX30), doxycycline ‎‎(DO20) and amikacin (AK30). This research investigates the pathogenic bacteria impacting common ‎carp in floating cages within Diyala Governorate, Iraq. Sensitivity tests indicated significant resistance ‎rates to commercial broad-spectrum antibiotics, underscoring their prevalence, impact on fish health, and ‎implications for management strategies.‎