Quinolone resistance mechanisms among extended-spectrum beta-lacta- mase (ESBL)-producing Escherichia coli isolated from farm animals in Switzerland.

Abstract

Sixty extended-spectrum b-lactamase (ESBL)-producing Escherichia coli isolated from rivers and lakes in Switzerland were screened for individual strains additionally exhibiting a reduced quinolone susceptibility phenotype. Totally, 42 such isolates were found and further characterized for their molecular (fluoro)quinolone resistance mechanisms. PCR and sequence analysis were performed to identify chromosomal mutations in the quinolone resistance-determining regions (QRDR) of gyrA, gyrB, parC and parE and to describe the occurrence of the following plasmid-mediated quinolone resistance genes: qepA, aac-69-Ib-cr, qnrA, qnrB, qnrC, qnrD and qnrS. The contribution of efflux pumps to the resistance phenotype of selected strains was further determined by the broth microdilution method in the presence and absence of the efflux pump inhibitor phe-arg-b-naphthylamide (PAbN). Almost all strains, except two isolates, showed at least one mutation in the QRDR of gyrA. Ten strains showed only one mutation in gyrA, whereas thirty isolates exhibited up to four mutations in the QRDR of gyrA, parC and/or parE. No mutations were detected in gyrB. Most frequently the amino-acid substitution Ser83RLeu was detected in GyrA followed by Asp87RAsn in GyrA, Ser80RIle in ParC, Glu84RVal in ParC and Ser458RAla in ParE. Plasmidmediated quinolone resistance mechanisms were found in twenty isolates bearing QnrS1 (4/20), AAC-69-Ib-cr (15/20) and QepA (1/20) determinants, respectively. No qnrA, qnrB, qnrC and qnrD were found. In the presence of PAbN, the MICs of nalidixic acid were decreased 4to 32-fold. (Fluoro) quinolone resistance is due to various mechanisms frequently associated with ESBL-production in E. coli from surface waters in Switzerland. Citation: Zurfluh K, Abgottspon H, Hachler H, Nuesch-Inderbinen M, Stephan R (2014) Quinolone Resistance Mechanisms among Extended-Spectrum BetaLactamase (ESBL) Producing Escherichia coli Isolated from Rivers and Lakes in Switzerland. PLoS ONE 9(4): e95864. doi:10.1371/journal.pone.0095864 Editor: Asad U. Khan, Aligarh Muslim University, India Received October 5, 2013; Accepted April 1, 2014; Published April 22, 2014 Copyright: 2014 Zurfluh et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors thank the Swiss Federal Office for Public Health, Division Communicable Diseases, for partial financial support. No additional funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: stephanr@fsafety.uzh.ch