Antimicrobial activity of a new fluoroquinolone, DU-6859a, against quinolone-resistant clinical isolates of Neisseria gonorrhoeae with genetic alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV

The in-vitro antimicrobial activity of DU-6859a, a new fluoroquinolone, was tested against 55 clinical isolates of Neisseria gonorrhoeae. The MIC of DU-6859a inhibiting 90% (MIC90) of the isolates with genetic alterations of both the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV was 0.125 mg/L. The MIC90 for isolates with alterations of GyrA alone or without alterations of GyrA or ParC was 0.03 mg/L and 0.004 mg/L, respectively. The potency of DU-6859a against clinical isolates bearing genetic alterations associated with quinolone resistance was significantly greater than that of currently available fluoroquinolones.