JAC Advance Access originally published online on March 13, 2008
Journal of Antimicrobial Chemotherapy 2008 61(6):1240-1243; doi:10.1093/jac/dkn115
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Original research |
Qnr-like pentapeptide repeat proteins in Gram-positive bacteria
1 Department of Microbiology, University of Seville, Seville, Spain 2 Service of Microbiology, University Hospital Virgen Macarena, Seville, Spain
Received 21 November 2007; returned 18 January 2008; revised 7 February 2008; accepted 22 February 2008
* Corresponding author. Tel: +34-954-55-28-63; Fax: +34-954-37-74-13; E-mail: jmrodriguez{at}us.es
Objectives: To study the role of Qnr-like pentapeptide repeat proteins (PRPs) from several Gram-positive species with quinolone resistance in vitro.
Methods: A PCR-based strategy was used to clone and express genes coding for Qnr-like PRPs in Enterococcus faecalis, Enterococcus faecium, Listeria monocytogenes, Clostridium perfringens, C. difficile, Bacillus cereus and B. subtilis in Escherichia coli DH10B. MIC values of nalidixic acid and fluoroquinolones were determined for reference strains and E. coli DH10B harbouring recombinant plasmids containing genes coding for PRPs.
Results: Amino acid identity of Qnr-like PRPs in Gram-positive strains compared with that of the plasmid-mediated quinolone resistance determinants QnrA1, QnrB1 and QnrS1 was in the range of 16% to 22%. Recombinant plasmids coding for Qnr-like PRPs conferred reduced susceptibility to fluoroquinolones (in the range of 0.016 to 0.064 mg/L for ciprofloxacin) and nalidixic acid (from 6 to 12 mg/L), depending on the antimicrobial agent and PRP. The PRP from B. subtilis showed no protective effect.
Conclusions: The PRPs analysed conferred a reduced susceptibility phenotype in E. coli; the data provide further evidence of the possible roles in quinolone resistance of PRPs from different Gram-positive species. These Gram-positive species may constitute a reservoir for Qnr-like quinolone resistance proteins.
Keywords: fluoroquinolones , resistance , plasmids
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