Surveillance for plasmid-mediated quinolone resistance determinants in Enterobacteriaceae within the Calgary Health Region, Canada: The emergence of aac(6′)-Ib-cr

Abstract

Objectives: A study was designed to determine the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants among clinical isolates of Enterobacteriaceae from the Calgary Health Region (CHR). Methods: During January and February 2004 and January and February 2007, 564 non-repeat isolates of Escherichia coli, Klebsiella spp., Proteus mirabilis and Morganella morganii resistant to ciprofloxacin and/or tobramycin were screened for PMQR determinants using a multiplex PCR for qnrA, qnrS and qnrB and aac(6′)-Ib genes; aac(6′)-Ib-cr was further identified by digestion with Bst F5I. Results: In 2004, 6/139 (4%) of the resistant E. coli were positive for aac (6′)-Ib-cr. In 2007, 53/398 (13%) were positive for aac(6′)-Ib-cr, 3/398 (0.8%) were positive for qnrS, and one isolate was positive for both. All the isolates were present in urines and the majority [40/63 (63%)] were submitted from community collection sites; 8 (13%) isolates co-produced AmpC β-lactamases and 34 (54%) co-produced CTX-M-15. aac(6′)-Ib-cr was present in one Klebsiella pneumoniae and one P. mirabilis, whereas one isolate of K. pneumoniae was positive for both aac(6′)-Ib-cr and qnrB. Conclusions: Our results showed that isolates with aac(6′)-Ib-cr, often associated with CTX-M-15, are emerging among fluoroquinolone-resistant E. coli in the CHR. Our study suggests that surveillance for PMQR determinants should be undertaken on a regular basis. © The Author 2008. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.