Grepafloxacin, a Dimethyl Derivative of Ciprofloxacin, Acts Preferentially through Gyrase in Streptococcus pneumoniae : Role of the C-5 Group in Target Specificity

Abstract
Grepafloxacin, a 5- methyl -7-piperazinyl-3"- methyl analogue of ciprofloxacin, was used to obtain stepwise-selected mutants of Streptococcus pneumoniae 7785. Analysis of the quinolone resistance-determining regions of the gyrA , gyrB , parC , and parE genes in these mutants revealed that gyrA mutations preceded those in parC . Given that ciprofloxacin (5- H ,7-piperazinyl) and AM-1121 (5- H ,7-piperazinyl-3"- methyl ) both act through topoisomerase IV, we conclude that the 5- methyl group of grepafloxacin favors gyrase in S. pneumoniae .

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