Fish farming provides food and livelihood for many people around the world. The fact that trout is produced in many parts of the world and has a very rich content in terms of nutritional value increases the importance of trout. However, there are many problems in trout production due to bacterial factors, making fish production extremely difficult. Bacterial factors cause significant fish deaths and economic losses such as slowdown in growth. In addition to these, these factors also cause some damage to the DNA of fish and the formation of oxidations by disrupting the balance of free radicals in the tissues. Therefore, in this study; In the trout farms in our province, the trout with the main bacterial agents causing infection were determined and bacterial species (Staphylococcus epidermidis, Lactococcus garvieae and Bacillius subtilis) were determined by PCR. The brain and liver tissues of these fish were taken and the changes in antioxidant enzyme levels (SOD, CAT, GSH-Px), lipid peroxidation (MDA) and damage to their DNA (8-OHdG) compared to the control groups were investigated. In the study, it was determined that the antioxidant defense system enzyme levels in all three species of bacteria decreased in tissues, while lipid peroxidation and 8-OHdG levels increased.
 As a result; Staphylococcus epidermidis, Lactococcus garvieae and Bacillius
 subtilis bacteria caused changes in antioxidant enzyme levels, lipid peroxidation and 8-OHdG levels in trout brain and liver tissues.
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