Determination of isolated bacterial disease causes,antibiotic resistance genes and the antimicrobial effects of some endemic marjoram (Origanum spp.) species oils against agents in rainbow trout (Oncorhynchus mykiss Walbaum 1792) farm operating from the west mediterranean region

In this thesis study, some bacteria that are frequently seen and cause economic losses in rainbow trout (Oncorhynchus mykiss, Walbaum 1792) farms operating in the Western Mediterranean Region were isolated and first the resistance genes against various antibiotics found in these bacteria were identified as floR, ermA, ermB, tetA, tetE, tetM, sulI, sulII and sulIII and secondly to determine the antimicrobial effects of essential oils of O. minutiflorum, O. saccatum and O. bilgeri, which are Origanum species endemic to our country, against these bacteria. Microbiological cultivation was performed on bacterial samples taken from 108 rainbow trout showing disease symptoms collected from the provinces of the Western Mediterranean Region, and the bacterial species Aeromonas hydrophila, Lactococcus garvieae and Yersinia ruckeri, which are the causative agents of diseases such as yersiniosis, lactococcosis and motile aeromonas septicemia, which cause economic losses in rainbow trout, were examined using molecular biological methods. It was diagnosed by PCR method. Additionally, these findings were confirmed by the bacterial protein analysis method with matrix-mediated laser desorption ionization time-of-flight mass spectrometry MALDI TOF (Bruker Microflex). The antibiotic susceptibilities of the isolated and identified bacteria were determined by disk diffusion method using the antibiotics erythromycin (15 µg), florfenicol (30 µg), tetracycline (30 µg), sulfametxasol (100 µg) and sulfamethaxasol-trimethoprim (25 µg). In addition, the antimicrobial effects and minimum inhibition concentration (MIC) values of these three identified bacterial species against the essential oils of endemic O. minutiflorum, O. saccatum and O. bilgeri obtained in this study were studied. As a result, it was determined that these bacterial species were sensitive to the antibiotics erythromycin (15 µg), florfenicol (30 µg), tetracycline (30 µg), sulfamethaxsol (100 µg) and sulfamethaxsol-trimethoprim (25 µg), while the most effective antibiotic was florfenicol (30 µg). has been observed. The average antibiotic zone diameters of florfenicol (30 µg) for Aeromonas hydrophila, Lactococcus garvieae and Yersinia ruckeri bacteria were determined as 31.0 mm, 23.0 mm and 30.0 mm, respectively. Among the bacteria, Y. ruckeri (tetA,sulI and sulII), L. garvieae (floR, ermA, ermB, tetA, tetE, tetM, sulI, sulII and sulIII) and Aeromonas hydrophila (sulII) were determined to carry antibiotic resistance genes with the help of specific primers and PCR bands has been made. In addition, it was determined that endemic O. minutiflorum, O. saccatum and O. bilgeri essential oils had an antimicrobial effect on the studied bacteria, and that O. saccatum oil had less antimicrobial effect than O. minutiflorum and O. bilgeri oil, while O. minutiflorum and O. bilgeri oils had less antimicrobial effects. It has been determined that oil has a strong antimicrobial effect. The minimum inhibition concentration value of endemic Origanum essential oils on A. hydrophila, L. garvieae ve Y. ruckeri bacteria species were determined to be 3.90 µl/mL for O. saccatum oil and 1.90 µl/mL for O. bilgeri and O. minutiflorum oils.