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Journal of Clinical Microbiology, July 2009, p. 2033-2039, Vol. 47, No. 7
0095-1137/09/$08.00+0 doi:10.1128/JCM.02229-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Service of Microbiology, University Hospital Marqués de Valdecilla, Santander,1 Department of Microbiology, School of Medicine, Seville,2 Department of Molecular Biology, School of Medicine, Santander,3 Service of Microbiology, University Hospital Virgen Macarena, Seville, Spain4
Received 19 November 2008/ Returned for modification 20 November 2008/ Accepted 14 April 2009
We have studied by PCR and DNA sequencing the presence of the qnrA, qnrB, qnrS, aac(6')-Ib-cr, qepA, intI1, and ISCR1 genes in 200 clinical isolates of Enterobacter cloacae (n = 153) and E. aerogenes (n = 47) consecutively collected between January 2004 and October 2005 in two hospitals located in Santander (northern Spain) and Seville (southern Spain). Mutations in the quinolone resistance-determining region of gyrA and parC also were investigated in organisms containing plasmid-mediated quinolone resistance genes. The isolates had different resistant phenotypes, including AmpC hyperproduction, extended-spectrum β-lactamase production, resistance or decreased susceptibility to quinolones, and/or resistance to aminoglycosides. Among the 116 E. cloacae isolates from Santander, qnrS1, qnrB5, qnrB2, and aac(6')-Ib-cr were detected in 22 (19%), 1 (0.9%), 1 (0.9%), and 3 (2.6%) isolates, respectively. Twenty-one, 17, and 2 qnrS1-positive isolates also contained blaLAP-1, intI1, and ISCR1, respectively. A qnrB7-like gene was detected in one E. aerogenes isolate from Santander. No plasmid-mediated quinolone resistance gene was detected in the isolates from Seville. The qnrS1-containing isolates corresponded to four pulsed-field gel electrophoresis patterns and showed various levels of resistance to quinolones. Six isolates were susceptible to nalidixic acid and presented reduced susceptibility to ciprofloxacin. The qnrS1 gene was contained in a conjugative plasmid of ca. 110 kb, and when the plasmid was transferred to recipient strains that did not have a specific mechanism of quinolone resistance, the ciprofloxacin MICs ranged from 0.047 to 0.125 µg/ml.
Published ahead of print on 22 April 2009.
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