Activity of gemifloxacin against penicillin- and ciprofloxacin-resistant Streptococcus pneumoniae displaying topoisomerase- and efflux-mediated resistance mechanisms

Nine penicillin-resistant Streptococcus pneumoniae clinical isolates from N orthern Ireland, resistant to ciprofloxacin (MICs, 2 to 6 1 mu g/ml) throug h topoisomerase- and/or reserpine-sensitive efflux mechanisms, Here highly susceptible to gemifloxacin (MICs, 0.03 to 0.12 mu g/ml). Two strains (requ iring a ciprofloxacin MIC of 64 mu g/ml) carried known quinolone resistance mutations in parC, parE, and gyrB, resulting in S79F, D435V, and E474K cha nges, respectively. Thus, gemifloxacin is active against clinical strains e xhibiting altered topoisomerase and efflux phenotypes.