JAC Advance Access published online on June 13, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn237
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Original research |
Plasmid-mediated quinolone resistance determinants among enterobacterial isolates from outpatients in Brazil
1 Service de Bactériologie-Virologie, INSERM U914 ‘Emerging Resistance to Antibiotics’, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Université Paris XI, 78, rue du Général Leclerc, 94275 K.-Bicêtre, France 2 Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, USP, Ribeirão Preto, SP 14040-903, Brazil
Received 8 January 2008; returned 8 May 2008; revised 14 February 2008; accepted 15 May 2008
* Corresponding author. Tel: +33-1-45-21-36-32; Fax: +33-1-45-21-63-40; E-mail: nordmann.patrice{at}bct.aphp.fr
Objectives: The aim of this study was to determine the spread of plasmid-mediated quinolone resistance determinants [qnr-like, aac(6')-Ib-cr and qepA genes] among nalidixic acid-resistant enterobacterial strains isolated from outpatients from Southeast Brazil, their transferability and the genetic structures associated with the qnr genes.
Methods: The qnrA, qnrB and qnrS genes were screened by a multiplex PCR-based technique from 257 non-repetitive nalidixic acid-resistant enterobacterial isolates collected from January 2000 to May 2005. Conjugation experiments were performed to determine whether the qnr-carrying plasmids were self-transferable. Genetic structures surrounding the qnr genes were analysed by PCR and cloning. The aac(6')-Ib-cr and qepA genes were screened among qnr-positive strains.
Results: Six qnrB-like-positive isolates (2.3%) were detected, whereas no qnrA- or qnrS-positive isolates were detected. Three Escherichia coli and two Klebsiella pneumoniae isolates harboured a qnrB2 gene and a single Citrobacter freundii isolate had the qnrB8 gene. One qnrB2-positive isolate also had the extended-spectrum β-lactamase blaCTX-M-2 gene. All these isolates also possessed chromosomal substitutions in gyrase- and topoisomerase-encoding genes, explaining their high-level resistance to quinolones.
Conclusions: This study constitutes the first epidemiological survey of the three known Qnr determinants among Brazilian isolates and shows their low prevalence in that country, with the qnrB2 gene being mostly identified.
Key Words: Qnr , Latin America , prevalence
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