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KMID : 0603820070130020141
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Journal of Experimental & Biomedical Science
2007 Volume.13 No. 2 p.141 ~ p.148
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gyrA and gyrB Mutations in Quinolone-resistant Strains of Enterobacteriaceae Isolated from General Hospitals in Busan
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Kim Yun-Tae
Kim Tae-Un
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Abstract
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We determined the sequences of the quinolone resistance-determining region (QRDR) of gyrA and gyrB for 21 clinical strains of Enterobacteriaceae resistant to ciprofloxacin, norfloxacin and levofloxacin. The clinical strains were isolated from the specimens of three general hospitals in Busan. In the present study, we found mutations in type II topoisomerase (DNA gyrase) genes for all strains. We confirmed that some genera of Enterobacteriaceae of clinical specimen exhibited decreased sensitivity to fluroquinolone due to changes in Ser-83rightarrowLeu and Asp-87rightarrowAsn types on gyrA and alterations in Glu-465rightarrowArg and Ser-492rightarrowAsn type on gyrB. All the twenty-one strains had a missense mutation in gyrA (codon 83 and 87). Three of them had an additional mutation in gyrB (codon 465 or 492), but one of them had an additional mutation in gyrB (codon 426, 427, 491, 495 and 496). The strains which had two mutations in type II topoisomerase genes (gyrA and gyrB) were significantly more resistant to fluoroquinolones than those with a single mutation in gyrA (mean MICs of ciprofloxacin: geq8mug/ml, mean MICs of levofloxacin: geq16mug/ml). Interestingly, the examination of silent nucleotide changes n the gyrA and gyrB genes revealed six different patterns of DNA polymorphism, respectively. Fifteen strains of the twenty-one strains bearing the gyrase A mutation shared the same polymorphism and eleven strains of the twenty-one strains bearing the gyrase B mutation shared the same polymorphism.
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KEYWORD
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Quinolone resistance-determining region (QRDR), Type II topoisomerase, Mutation, GyrA, GyrB, Polymorphism
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