title: Extended spectrum of quinolone resistance, even to a potential latter third-generation agent, as a result of a minimum of two GrlA and two GyrA alterations in quinolone-resistant Staphylococcus aureus.
abstract: BACKGROUND
  This study was performed to determine the extended spectrum of quinolone resistance caused by increased mutations within the target enzymes of quinolones.
  
  
  METHODS
  The minimum inhibitory concentrations (MICs) for ciprofloxacin, sparfloxacin, trovafloxacin and DW286 were determined against 98 ciprofloxacin-resistant Staphylococcus aureus strains. Also, PCR-amplified grlA, grlB, gyrA and gyrB DNA fragments were sequenced and amino acid changes were analyzed.
  
  
  RESULTS
  The MIC(50) values of quinolones decreased with later-generation compounds, i.e. >or=64 microg/ml for ciprofloxacin, 16 microg/ml for sparfloxacin, 2 microg/ml for trovafloxacin and 0.25 microg/ml for DW286. Combinations of amino acid changes within GrlA (Ser-80, Tyr-83 or Glu-84), GrlB (Pro-451, Pro-585 or Asp-432) and GyrA (Ser-84, Ser-85 or Glu-88) were constructed. The combination of Ser-80-->Phe within GrlA and Ser-84-->Leu within GyrA was the fundamental combination in alterations involved in ciprofloxacin resistance, and additional alterations extended quinolone resistance.
  
  
  CONCLUSIONS
  A larger number of alterations within GrlA and GyrA further extended the spectrum of quinolone resistance.
authors.affiliation: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea.
authors.forename: Eun-Jeong
authors.initials: EJ
authors.lastname: Yoon
authors.forename: Chun-Yeong
authors.initials: CY
authors.lastname: Lee
authors.forename: Mi-Ja
authors.initials: MJ
authors.lastname: Shim
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Min
authors.forename: Ae-Ran
authors.initials: AR
authors.lastname: Kwon
authors.forename: Jongseo
authors.initials: J
authors.lastname: Lee
authors.forename: Eung-Chil
authors.initials: EC
authors.lastname: Choi
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D004269:DNA, Bacterial; D024881:Drug Resistance, Bacterial / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; C513430:GrlA protein, E coli; D015534:Trans-Activators; D027081:DNA Gyrase