Introduction: Fluoroquinolone are broad-spectrum antimicrobial agents extensively used by physicians. This widespread use has been associated with increased level ofquinolone resistance strains, particularly in Enterobacteriaceae. Plasmid-mediated quinolone resistance (PMQR) including Qnr determinants with the potential for horizontal transfer confer to quinolone resistance. Plasmid harboring qnr genes may also encode extended-spectrum beta-lactamases (ESBLs) such as CTX-M, SHV and TEM type. The prevalence ofplasmid-mediated quinolone resistance (PMQR) determinants like qnrA, qnrB and qnrS was investigated in a collection of 215 Enterobacteriaceae strains with reduced susceptibility to fluoroquinolone.
Methods: The isolates (n=215) were collected from 1 March to 31 September, 2010 in a regular hospital in Warsaw, Poland. The resistance to nalidixic acid, norfloxacin and ciprofloxacin was determinated by twofold agar dilution method, while MICs of moxifloxacin were examined by using E-test. The prevalence of qnrA, qnrB, qnrS, blaCTX-M, blaSHV and blaiTEM was evaluated by PCR. All PCR-products for qnr were sequenced. The epidemiological relationship between positive isolates was studied by PFGE method.
Results: Eighteen isolates (8,3%) carried the qnr gene encoding the QnrA, QnrB or QnrS. The coexistence of both qnrA and qnrS genes was noted in one isolate of E. coli. The qnrB gene was the most common qnr type found. All the Qnr-producing strains were simultaneously resistant to naldixic acid and different - level non-susceptible fluoroquinolone (MIC CIP 1.5-1024 microg/ml). Most of qnr-positive strains (88.9%) were extended-spectrum beta-lactamase (ESBL) producers of CTX-M and TEM types predominantly.
Conclusions: The present study highlights the wide spread of Qnr-like determinants in clinical Enterobacteriaceae non-susceptible to fluoroquinolone in Poland, with an association with the ESBL.