Molecular analysis of antimicrobial resistance in Yersinia ruckeri strains isolated from rainbow trout (Oncorhynchus mykiss) grown in commercial fish farms in Turkey

In this study, molecular characterization of antimicrobial resistance of 116 Yersinia ruckeri strains isolated from rainbow trout (Oncorhynchus mykiss) with enteric redmouth disease (ERM) in commercial fish farms in the Northern and Eastern regions of Turkey was performed. The putative Y. ruckeri strains isolated were confirmed by PCR assays specific to the 16S rRNA gene of bacterium Y. ruckeri. Eighty-six (74.1%) strains were identified to belong to serovar 01 by agglutination test in which type 01 antibody was used. No strains carried antimicrobial gene cassettes inserted into integrons. Neither TEM- nor SHV-type beta-lactamase gene was found in ampicillin-resistant strains (33/116). tetA and tetB genes were screened in 41/116 oxytetracycline-resistant strains by PCR, and it was found that 21 (51.2%) carried a tetA and/or tetB gene. We conclude that the antimicrobial resistant Y. ruckeri strains may act as a reservoir of antimicrobial resistance genes within fish farm environments.