Diagnostics and antibiotic resistance of Yersinia ruckeri strains isolated from trout fish farms in Bulgaria

The study included 12 Yersinia ruckeri isolates from rainbow trout with symptoms of yersiniosis. Phenotypic and genotypic analysis of the isolates were performed by conventional microbiological, biochemical and molecular methods. Identification was confirmed by PCR using Y. ruckeri-specific primers and antibiotic resistance profiles were determined. Some isolates were found to be resistant to florfenicol, erythromycin, and oxytetracycline, which are licensed for use in fish farms. The obtained results will serve as basis for development of a local diagnostic scheme and strategy to fight against Yersinia ruckeri.