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M. Amato, A. Climent-Flores, Sr., S. Muñoz-Salas, M. Matías-Florentino, H. Mejía-López; Alterations in the QRDR of GyrA Responsible for the Resistance to Quinolones in Isolated of Multi-Treated Ophthalmic Injuries. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5532.
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The quinolones are antibacterial agents that have as targets two essential bacterial enzymes, DNA gyrase and DNA topoisomerase IV. Gyrase controls DNA supercoiling and relieves topological stress arising from the translocation of transcription and replication complexes along DNA. The forth-generation fluoroquinolones has been introduced by their high antimicrobial effectiveness. These on have an broad spectrum by the substitution of the metoxi C-8 group, which restricts the selection of resistant mutants in the wild pathogenic population. In this work it was studied the quinolone-resistance determining region (QRDR) of the A and B subunits of gyrase (gyrA and gyrB) in clinical isolated from multi-treated ophthalmic injuries
By culture and biochemical tests the isolated from conjunctivitis, keratitis and blefaritis were identified. Minimum inhibitory concentrations (MICs) were determined by epsilometry for ciprofloxacin (CIP), ofloxacin (OFL), gatifloxacin (GAT) and Moxifloxacin (MOX); (scale of 0.002 to 32 µg/ml) . The study of QRDR of gyrA and gyrB were made by automated sequencing.
Were identified 28 strains of Staphilococcus sp and the 68% of them had MIC >32µg/ml. The sequencing analysis showed point mutations Ser-84 to Leu located in the gyrA gene in 8 strains, 50% of them, presented resistance to all of tested quinolones and the other 50% had MIC >32µg/ml for CIP and OFL and MIC ≤ 4µg/ml to GAT and MOXI. One strain had a Glu-88 to Lys mutation and it was resistance for all the quinolones. No mutations occurred in the gyrB gen for anyone strains.
Poor literature data show bacterial quinolones resistance in responsible microorganisms of ophthalmic injuries. The multiresistant strain are common and in this work we show a high percentage of resistance strain to first, second, and fourth-generation of quinolones, then, is necessary to practice the antibiotics susceptibility in all clinical multi-treated case.In this sample we found Ser-84 to Leu and Glu-88 to Lys mutations in gyrA gen. Another QRDR like parC of topoisomerase IV could be implicated in the resistance observed in the studied sample.
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