The prevalence of plasmid-mediated quinolone resistance genes in Chryseobacterium aquaticum isolated from farmed salmonids in Turkey

Introduction: The aquatic environment can serve both as a natural reservoir of antibiotic resistancegenes and the spreading of bacteria and antimicrobial resistance genes to environment.Plasmid-mediated quinolone resistance (PMQR) genes represent an important challenge to theeffectiveness of quinolones in the treatment of human and animal infections. In this study, 70Chrysobacterium aquaticum isolates recovered from farmed salmonids in Turkey were analyzedfor PMQR genes.Methodology: C. aquaticum strains were recovered from farmed salmonids in Turkey, 2013-2017 and identified with 16S rRNA sequence analysis. Quinolone susceptibility among thestrains was determined using minimum inhibitory concentration method against oxolinic acid,and the frequency of PMQR genes (qnrA, qnrB, qnrS) was investigated by PCR.Results: The isolates recovered from farmed rainbow trout exhibiting clinical signs such asdarkening of skin color, exophthalmia, and caudal fin root were identified as C. aquaticum.The rates of reduced susceptibility in phenotypically were determined for oxolinic acid (89%).Of the 70 isolates, 28 (40%) isolates harbored qnrA, 23 isolates (32%) harbored qnrS and 17isolates (24%) have both qnrA and qnrS. None of the isolates harbored qnrB.Conclusion: This is the first report of C. aquaticum recovered from rainbow trout in Turkey.Its pathogenicity was not assessed previously. Further research is needed for determining thevirulence mechanisms and pathogenesis of C. aquaticum. Our findings showed high rates ofquinolone resistance (89%) and qnr genes, underlining the importance of aquatic environmentas reservoirs for the dissemination of potentially possible C. aquaticum and horizontal genetransfer between other waterborne bacterial species. Other possible mechanisms of resistanceshould also be investigated for better characterization of quinolone-resistant C. aquaticumisolates.Keywords: Chrysobacterium aquaticum, antimicrobial resistance, rainbow trout, plasmid-mediatedquinolone resistance genesFunding: The Research Fund of Erciyes University, project number TCD-2018-8586.