19th International Conference on Diseases of Fish and Shellfish, Porto, Portugal, 9 - 12 September 2019, pp.108
Introduction: The aquatic environment can serve both as a natural reservoir of antibiotic resistance
genes and the spreading of bacteria and antimicrobial resistance genes to environment.
Plasmid-mediated quinolone resistance (PMQR) genes represent an important challenge to the
effectiveness of quinolones in the treatment of human and animal infections. In this study, 70
Chrysobacterium aquaticum isolates recovered from farmed salmonids in Turkey were analyzed
for 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 the
strains 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 as
darkening 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 17
isolates (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 the
virulence mechanisms and pathogenesis of C. aquaticum. Our findings showed high rates of
quinolone resistance (89%) and qnr genes, underlining the importance of aquatic environment
as reservoirs for the dissemination of potentially possible C. aquaticum and horizontal gene
transfer between other waterborne bacterial species. Other possible mechanisms of resistance
should also be investigated for better characterization of quinolone-resistant C. aquaticum
Keywords: Chrysobacterium aquaticum, antimicrobial resistance, rainbow trout, plasmid-mediated
quinolone resistance genes
Funding: The Research Fund of Erciyes University, project number TCD-2018-8586.