In-vitro antimicrobial activity of HSR-903, a new fluoroquinolone, against clinical isolates of Neisseria gonorrhoeae with quinolone resistance-associated alterations in GyrA and ParC.

The in-vitro antimicrobial activity of HSR-903, a new fluoroquinolone, was tested against 51 clinical Neisseria gonorrhoeae isolates in comparison with ciprofloxacin, levofloxacin and sparfloxacin. The MICs of HSR-903 for 11 isolates with alterations in both GyrA and ParC, for 19 isolates with alterations only in GyrA and for 21 isolates without alterations in either GyrA or ParC ranged from 0.03 mg/L to 1.0 mg/L (MIC90 = 0.25 mg/L), from 0.03 mg/L to 0.5 mg/L (MIC90 = 0.125 mg/L) and from < or = 0.001 mg/L to 0.008 mg/L (MIC90 = 0.004 mg/L), respectively. Levofloxacin and ciprofloxacin were the least active of the four quinolones tested, particularly against the mutant strains. Sparfloxacin was more active, but HSR-903 exhibited the most potent in-vitro activity against the clinical N. gonorrhoeae isolates, including those harbouring quinolone-resistance-associated alterations in GyrA and ParC.