Title The Mechanism of Quinolone Resistance in Staphylococcus aureus
Author Lee, Youngyeong · Kong, Jaeyang · Rhee, Youngha1 · Kim Eunhee2
Address Korea Research Institute of Chemical Technology, Pharmaceutic Screening Laboratory; 1Department of Microbiology, College of Natural Sciences, Chyngnam National University; 2Department og Genetic Engineering, College of Science and Engineering, Pai-chai University
Bibliography Korean Journal of Microbiology, 30(5),360-365, 1992
Key Words Staphylococcus aureus, gyrA, quinolone, resistance
Abstract Clinical isolates of 8 ofloxacin resistant Staphylococcus auresu (ORSA) were subjected to MIC test, Southern analysis on gyrA locus and nucleotide sequence analysis of 290 bp of gyrA gene (gyrA-290) spanning amino acid 26 to 121 in order to understand the mechanism of quinolone resistance in Staphylococcus aureus. ORSAs showed highlevel resistance against quinolones (8-250 fold increase of MICs) and also significant resistance agianst β-lactams (2-32 fold increase of MICs). However, ORSs did not show any change in sensitivity agianst vancomycin. Southern analysis of ORSAs with HindIII, PstI and AluI revealed RFLPs on gyrA locus. In order to further analyze the gyrA gene,m gyrA-290 was amplified by PCR and cloned to pTZ vector. Subsequent nucleic acid sequence analysis of gyrA-290 demonstrated a point mutation of C to T resulting amino acid change of Ser-84 to Leu-84 in all 8 ORSA strains. The substitution at 84th amino acid of tyrase A might confer one mechanism of high level quinolone resistance in Staphylococcus aureus.
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