Detection of Naturally Infected Rainbow Trouts (Oncorhynchus mykiss Walbaum, 1792) by Lactococcus garvieae with Molecular Methods and Culture Techniques and Determination of Antibiotic Susceptibility Profiles of Agent in a Trout Farm

In this case report, 8 fish samples taken from a commercial Rainbow trout farm during outbreak in the Black Sea Region were investigated. Causal agent of the outbreak was detected and its antibiotic susceptibility profile was investigated. The outbreak was observed at 21oC temperature in August, 2014. The 70-75 % mortality rate was caused by the agent in a month. Lactococcus garvieae were isolated from liver, spleen and kidney of 4 fish on the Tryptic Soy Agar, McConkey Agar and Shotts-Waltman Agar as the result of bacteriological examinations. Isolated strains were identified by biochemical tests and were confirmed by molecular methods. Similar phenotypic properties were shared by outbreak isolates. All the strains were sensitive to florfenicol, erythromycin, oxytetracycline, amoxicillin, ampicillin while all strains were resistant to trimethoprim, sulfamethoxazole/trimethoprim and oxolinic acid. The sensitivity of enrofloxacin, cefoperazone, kanamycin, neomycin, and gentamicin were determined at varying rates. Multidrug resistance was also detected in all the strains.