A Comparative In Vitro Surveillance Study of Gemifloxacin Activities against 2,632 Recent Streptococcus pneumoniae Isolates from across Europe, North America, and South America

From 1997 to 1999, 94 study centers in 15 European, 3 North American, and 2 South American countries contributed 2,632 isolates of Streptococcus pneumoniae to an international antimicrobial susceptibility testing study. Only 62.0% of isolates were susceptible to penicillin, while 22.3% were penicillin intermediate and 15.6% were penicillin resistant. Resistance to trimethoprim-sulfamethoxazole (24.4%), azithromycin (26.0%), and clarithromycin (27.1%) was also highly prevalent. For the penicillin-resistant isolates (n = 411), the MICs at which 90% of isolates are inhibited (MIC(90)s) for gemifloxacin, levofloxacin, ofloxacin, clarithromycin, and azithromycin were 0.03, 1, 2, >16, and >64 μg/ml, respectively. Similarly, for isolates resistant to both azithromycin and clarithromycin (n = 649), gemifloxacin, levofloxacin, ofloxacin, and penicillin MIC(90)s were 0.03, 1, 2, and 4 μg/ml, respectively. Overall rates of resistance to trovafloxacin (0.3%), levofloxacin (0.3%), grepafloxacin (0.6%), and ofloxacin (0.7%) were low. For ofloxacin-intermediate and -resistant isolates (n = 142), gemifloxacin had the lowest MIC(90) (0.12 μg/ml) compared to the MIC(90)s of trovafloxacin (0.5 μg/ml), grepafloxacin (1 μg/ml), and levofloxacin (2 μg/ml). For all S. pneumoniae isolates tested, gemifloxacin MICs were ≤0.5 μg/ml, suggesting that gemifloxacin has the potential to be used as a treatment for pneumococcal infections, including those arising from isolates resistant to β-lactams and macrolides.