Anti-gonococcal activity of gemifloxacin against fluoroquinolone-resistantstrains and a comparison of agar dilution and Etest methods

Gemifloxacin is a novel quinolone with excellent activity against Gram-posi tive and some Gram-negative pathogens. Its activity was tested against 150 Neisseria gonorrhoeae strains, including 50 ciprofloxacin-resistant isolate s, using reference agar dilution and Etest methods. Gemifloxacin was found to be highly potent against ciprofloxacin-susceptible strains (MIC90 0.008 mg/L), but was 16-fold less potent against ciprofloxacin-resistant gonococc i. The order of quinolone potency against these fluoroquinolone-resistant m utants was: gemifloxacin (MIC90 0.12 mg/L)> trovafloxacin (0.25 mg/L)> moxi floxacin = grepafloxacin (0.5 mg/L)> ciprofloxacin (1 mg/L). Etest and refe rence agar dilution MIC results showed excellent correlation (r = 0.96) and >98% of MICs were within +/-1 log(2) dilution step (essential agreement). The excellent potency of gemifloxacin indicates its potential for the treat ment of infections with quinolone-resistant N. gonorrhoeae.