Phenotypic and genotypic characterization of isolated Flavobacterium psychrophilum strains in rainbow trout cage farms in Kahramanmaraş city of Türkiye

This research aimed to characterize phenotypically and genotypically characterize Flavobacterium psychrophilum strains in juvenile rainbow trout (Oncorhynchus mykiss) from 68 cage farms located in Kahramanmaras, Türkiye. The present study was conducted from December 2022 to July 2023, with samples of juvenile fish (5 g or less) being collected alongside larger individuals. The isolation of the bacterium was achieved by employing Tryptone Yeast Salt Agar medium, which was then incubated at 15°C for a period of 5-7 days. The purification of yellow colonies was undertaken, and biochemical testing was conducted using the Biolog GENIII microplate system to evaluate the phenotypic traits. For the purpose of molecular validation, the identity of the strains initially identified by Biolog was confirmed by PCR with specific primers. All isolates underwent sequence analysis, and the resulting data were compared against NCBI reference sequences. Twelve strains of F. psychrophilum were conclusively identified through combined phenotypic and genotypic analysis.