Characterization of plasmid-mediated quinolone resistance determinants in Klebsiella pneumoniae and Escherichia coli from Tokai, Japan.

Abstract The spread of plasmid-mediated quinolone resistance (PMQR) determinants was evaluated in 150 ceftazidime or cefotaxime-resistant clinical isolates of Klebsiella pneumoniae and Escherichia coli from Tokai, Japan between 2008 and 2011. In this study, qnrB , qnrS, and aac(6′)-Ib-cr genes were detected in 12 (50.0%), 4 (16.7%), and 1 (4.2%) of 24 K. pneumoniae isolates, respectively, while qnrA , aac(6′)-Ib-cr , and qepA genes were detected in 1 (0.8%), 11 (8.7%), and 2 (1.6%) of 126 E. coli isolates, respectively. qnr genes were mainly found in K. pneumoniae (66.7%) and to a lesser extent in E. coli (0.8%). We determined the genetic environment of the qnrB4 gene in 24.6 kb class 1 integron structure, including aar-2 , cmlA , blaOXA-10 , aadA1 , qacEdelta1 , sul1 , and blaDHA-1 . In a time-kill assay, introduction of the qnrB4 or qnrS1 plasmid to the recipient E. coli strain decreased the bactericidal activities of fluoroquinolones such as ciprofloxacin, levofloxacin, and pazufloxacin.