Plasmid-mediated quinolone resistance in Salmonella serotypes isolated from chicken carcasses in Turkey

Quinolones have been extensively used for treatment of a variety of invasive and systemic infections of salmonellosis. Widespread use of these agents has been associated with the emergence and dissemination of quinolone-resistant pathogens. The quinolone resistance and plasmid-mediated quinolone resistance determinants (qnrA, qnrB, qnrS and aac(6')-Ib-cr) of 85 Salmonella isolates from chicken carcasses were investigated in this study. Isolates were serotyped according to the Kauffman-White-Le Minor scheme, and broth microdilution method was used to determine quinolone resistance. Plasmid-mediated quinolone resistance genes were investigated by real-time PCR and positive results were confirmed by sequencing. Among the Salmonella isolates, 30/85 (35%) and 18/85 (21%) were found to be resistant to enrofloxacin (MIC more than 2 mg/ml), and danofloxacin (MIC more than 2 mg/ml), respectively. All the isolates were negative for qnrA, qnrB and aac(6')-Ib-cr genes, nevertheless 2% (S. Brandenburg and S. Dabou) were positive for qnrS (qnrS1 determinant). This study is the first and unique investigating the plasmid- mediated quinolone resistance determinants of Salmonella isolated from chicken carcasses in Turkey.