Abstract
Stenotrophomonas maltophilia exhibits wide spectrum of fluoroquinolone resistance using different mechanisms as multidrug efflux pumps and Smqnr alleles. Here, the role of smeDEF, smeVWX efflux genes and contribution of Smqnr alleles in the development of fluoroquinolone resistance was assessed. Ciprofloxacin, levofloxacin and moxifloxacin resistance were found in 10.9%, 3.5%, and 1.6% of isolates, respectively. More than four-fold differences in ciprofloxacin MICs were detected in the presence of reserpine and smeD, F, V expression was significantly associated with ciprofloxacin resistance (p = 0.017 for smeD, 0.003 for smeF, and 0.001 for smeV). Smqnr gene was found in 52% of the ciprofloxacin-resistant isolates and Smqnr8 was the most common allele detected. Fluoroquinolone resistance in S. maltophilia clinical isolates was significantly associated with active efflux pumps. There was no correlation between the Smqnr alleles and ciprofloxacin resistance; however, contribution of the Smqnr genes in low-level levofloxacin resistance was revealed.
Highlights
Stenotrophomonas maltophilia exhibits wide spectrum of fluoroquinolone resistance using different mechanisms as multidrug efflux pumps and Smqnr alleles
S. maltophilia is intrinsically resistant to many commonly used antibiotics such as carbapenems and aminoglycosides and acquiring resistance to multiple antibiotics through plasmids, transposons, integrons result in the development of multi-drug resistant (MDR) strains, which makes it difficult to treat infections caused by this b acterium[4,5]
The genetic background of resistance to fluoroquinolones including the role of active efflux pumps and their gene expression, the effect of reserpine as an efflux pump inhibitor on minimum inhibitory concentrations (MICs), and association of Smqnr alleles with fluoroquinolone resistance in clinical isolates of S. maltophilia in Iran was sought
Summary
Stenotrophomonas maltophilia exhibits wide spectrum of fluoroquinolone resistance using different mechanisms as multidrug efflux pumps and Smqnr alleles. Fluoroquinolone resistance in S. maltophilia clinical isolates was significantly associated with active efflux pumps. Multiple chromosomally encoded resistance determinants, including efflux pumps, antibiotic-inactivating enzymes and the quinolone resistance protein SmQnr have been considered as the mechanisms of antibiotic resistance in S. maltophilia[12,13]. S. maltophilia harbors a novel quinolone resistance gene, namely Smqnr which is encoded by the chromosome, rather than plasmid-mediated qnr genes[15]. The genetic background of resistance to fluoroquinolones including the role of active efflux pumps and their gene expression, the effect of reserpine as an efflux pump inhibitor on minimum inhibitory concentrations (MICs), and association of Smqnr alleles with fluoroquinolone resistance in clinical isolates of S. maltophilia in Iran was sought
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