Although quinolone resistance results mostly from chromosomal mutations in Enterobacteriaceae, it may also be mediated by plasmid-encoded Qnr determinants. Qnr proteins protect DNA from quinolone binding and compromise the efficacy of quinolones such as nalidixic acid. Qnr proteins (QnrA-like, QnrB and QnrS) have been identified worldwide with a quite high prevalence among Asian isolates with a...

Sir, Chromosomal mutations in the topoisomerase II gene gyrA and altered drug accumulation were considered to be the only mechanisms of quinolone resistance until 1998, when the plasmidmediated quinolone resistance gene, qnrA, was described in an isolate of Klebsiella pneumoniae. Since then, other plasmidborne resistance genes, qnrB, qnrS (and their variants), aac(60)-Ib-cr and qepA, have been ...

Background and Objectives Since the fluoroquinolones are the broad-spectrum antibiotics, they affect both Gram-negative and Gram-positive bacteria. These antibiotics are widely prescribed by physicians. As a result, some bacteria, especially Enterobacteriaceae, have shown a resistance to this family of antibiotics. The current study aimed at detecting the frequency of qnrA, qnrB, and qnrS genes...

Fourteen strains of S. Typhi (n=13) and S. Paratyphi A (n=1) resistant to ciprofloxacin were compared with 30 ciprofloxacin decreased-susceptibility strains on the basis of qnr plasmid analysis, and nucleotide substitutions at gyrA, gyrB, parC and parE. In ciprofloxacin-resistant strains, five S. Typhi and a single S. Paratyphi A showed triple mutations in gyrA (Ser83-->Phe, Asp87-->Asn, Glu133...

Objective: Although quinolone resistance results mostly from chromosomal mutations in Klebsiella pneumoniae, it may also be mediated by plasmid – encoded qnr determinants. Plasmid-mediated quinolone resistance (PMQR) was increasingly identified in Enterobacteriaceae family worldwide. The aim of this study was to investigate the prevalence of qnr genes in clinical isolates of Klebsiella pn...

We searched for plasmid-mediated quinolone resistance determinants of the Qnr type in several water samples collected at diverse locations from the Seine River (Paris, France). The qnrS2 genes were identified from Aeromonas punctata subsp. punctata and A. media. The qnrS2 gene was located on IncU-type plasmids in both isolates, which resulted in increased MIC values of quinolones and fluoroquin...

Twenty-eight of the 302 Salmonella strains isolated from patients with overseas travelers' diarrhea who were examined at Kansai Airport Department Station during the 6-year period between 2001 and 2007 showed decreased susceptibility to both nalidixic acid (NA) and ciprofloxacin (CPFX) (MIC of NA, 16-64 microg/mL; MIC of CPFX, 0.064-2.0 microg/mL). These 28 strains revealed no variations in the...

Although resistance to quinolones is commonly chromosomally-encoded in Enterobacteriaceae, the emergence of plasmid-mediated quinolone resistance (PMQR) has also been reported, with at least three known resistance mechanisms to date, i.e., Qnr, aminoglycoside acetyltransferase AAC(6')-Ib-cr and QepA. Qnr proteins protect target enzymes (DNA gyrase and type IV topoisomerase) from quinolone inhib...

background :    klebsiella pneumoniae is among the most common and significant agents of community and hospital-acquired infections. plasmid mediated quinolone resistance (pmqr) was increasingly identified in enterobacteriaceae family worldwide. plasmid-mediated quinolone resistance (pmqr) was first reported in 1998 from a klebsiella pneumoniae isolate in the usa. till date, five qnr proteins h...