title: Dual targeting of DNA gyrase and topoisomerase IV: target interactions of garenoxacin (BMS-284756, T-3811ME), a new desfluoroquinolone.
abstract: We determined the target enzyme interactions of garenoxacin (BMS-284756, T-3811ME), a novel desfluoroquinolone, in Staphylococcus aureus by genetic and biochemical studies. We found garenoxacin to be four- to eightfold more active than ciprofloxacin against wild-type S. aureus. A single topoisomerase IV or gyrase mutation caused only a 2- to 4-fold increase in the MIC of garenoxacin, whereas a combination of mutations in both loci caused a substantial increase (128-fold). Overexpression of the NorA efflux pump had minimal effect on resistance to garenoxacin. With garenoxacin at twice the MIC, selection of resistant mutants (<7.4 x 10(-12) to 4.0 x 10(-11)) was 5 to 6 log units less than that with ciprofloxacin. Mutations inside or outside the quinolone resistance-determining regions (QRDR) of either topoisomerase IV, or gyrase, or both were selected in single-step mutants, suggesting dual targeting of topoisomerase IV and gyrase. Three of the novel mutations were shown by genetic experiments to be responsible for resistance. Studies with purified topoisomerase IV and gyrase from S. aureus also showed that garenoxacin had similar activity against topoisomerase IV and gyrase (50% inhibitory concentration, 1.25 to 2.5 and 1.25 micro g/ml, respectively), and although its activity against topoisomerase IV was 2-fold greater than that of ciprofloxacin, its activity against gyrase was 10-fold greater. This study provides the first genetic and biochemical data supporting the dual targeting of topoisomerase IV and gyrase in S. aureus by a quinolone as well as providing genetic proof for the expansion of the QRDRs to include the 5' terminus of grlB and the 3' terminus of gyrA.
authors.affiliation: Division of Infectious Disease and Medical Services, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114-2696, USA.
authors.forename: Dilek
authors.initials: D
authors.lastname: Ince
authors.forename: Xiamei
authors.initials: X
authors.lastname: Zhang
authors.forename: L Christine
authors.initials: LC
authors.lastname: Silver
authors.forename: David C
authors.initials: DC
authors.lastname: Hooper
mesh_terms: D000483:Alleles; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D003001:Cloning, Molecular; D027081:DNA Gyrase / Q000096:biosynthesis / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000037:antagonists & inhibitors* / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D024841:Fluoroquinolones; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007211:Indoles; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D010957:Plasmids / Q000187:drug effects / Q000235:genetics; D015363:Quinolones; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D059005:Topoisomerase II Inhibitors
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D007211:Indoles; D015363:Quinolones; D059005:Topoisomerase II Inhibitors; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; C419689:garenoxacin