TARGETING OF DNA GYRASE IN STREPTOCOCCUS-PNEUMONIAE BY SPARFLOXACIN -SELECTIVE TARGETING OF GYRASE OR TOPOISOMERASE-IV BY QUINOLONES

gyrA and parC mutations have been identified in Streptococcus pneumoni ae mutants stepwise selected for resistance to sparfloxacin, an antipn eumococcal fluoroquinolone. GyrA mutations (at the position equivalent to resistance hot spot Ser-83 in Escherichia coli GyrA) were found in all 17 first-step mutants examined and preceded DNA topoisomerase IV ParC mutations (at Ser-79 or Glu-83), which appeared only in second-st ep mutants. The targeting of gyrase by sparfloxacin in S. pneumoniae b ut of topoisomerase IV by ciprofloxacin indicates that target preferen ce can be altered by changes in quinolone structure.