In vitro activity of gemifloxacin compared with other antimicrobial agents against recent clinical isolates of streptococci.

This study investigated the in vitro activity of gemifloxacin (SB-265805) against 50 recent clinical isolates of Streptococcus pyogenes, Streptococcus agalactiae and viridans streptococci using the microdilution method. This activity was compared with that of the quinolone agents ofloxacin, ciprofloxacin, levofloxacin, trovafloxacin and grepafloxacin, and with that of penicillin, ampicillin, clarithromycin and azithromycin. Gemifloxacin was significantly more potent than the other quinolones tested. Its potency was equal to that of penicillin for S. agalactiae, and superior to that of penicillin for viridans streptococci. The MIC(50) of gemifloxacin for S. pyogenes (0.015 mg/L) was equal to that of penicillin, with an MIC(90) of 0.03 mg/L. Gemifloxacin was also active against isolates of S. agalactiae (MIC = 0.03-0.06 mg/L) and S. pyogenes (MIC = 0.03- 0.06 mg/L) with reduced susceptibility to ofloxacin (MIC = 4-8 mg/L) and grepafloxacin (MIC = 4 mg/L). These preliminary observations indicate that gemifloxacin is a promising antimicrobial agent for clinical use.