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.
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.
Yoon
Eun-Jeong
EJ
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea.
Lee
Chun-Yeong
CY
Shim
Mi-Ja
MJ
Min
Yu-Hong
YH
Kwon
Ae-Ran
AR
Lee
Jongseo
J
Choi
Eung-Chil
EC
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
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; C513430:GrlA protein, E coli; D015534:Trans-Activators; D027081:DNA Gyrase