Abstract
In this study, the bacteriological examination was done in case of disease suspect of rainbow trout (Oncorhynchus mykiss) which kept in cages in the Black Sea Region of Turkey. The bacterial agent was identified as Citrobacter braakii by rapid test kit (API 20E, Profile: 1704553), further identification was performed by 16S rRNA gene sequencing. Bacteria were identified as Citrobacter freundii by further molecular analysis. The antibacterial susceptibility of bacteria was also determined for 6 different antibiotics. The bacteria was sensitive to florfenicol, enrofloxacin, oxytetracycline and trimethoprim+sulfamethoxazole and resistant to erythromycin and amoxicillin-clavulanate. The most effective antibiotic was florfenicol. The disease was treated with florfenicol.