In vitro activity of grepafloxacin and 25 other antimicrobial agents against Streptococcus pneumoniae: correlation with penicillin resistance.

Strains of Streptococcus pneumoniae from the United States that were susceptible, intermediately resistant, or highly resistant to penicillin were tested for susceptibility to 26 antimicrobial agents that have been used or considered for the treatment of patients with pneumococcal infections. The drugs tested included penicillins, one penicillin/beta-lactamase inhibitor combination, cephalosporins, macrolides, a lincosamide, fluoroquinolones, and four miscellaneous drugs (vancomycin, rifampin, tetracycline, and trimethoprim-sulfamethoxazole). The activities of the penicillins and macrolide agents were similar, but the activities within the cephalosporin and fluoroquinolone classes were often dissimilar. For the fluoroquinolones, the order of in vitro activity, from most to least active, was grepafloxacin, sparfloxacin, levofloxacin, ciprofloxacin, and ofloxacin. Increased resistance to penicillin in the pneumococcal isolates studied correlated with increased resistance to other penicillins, cephalosporins, macrolides, clindamycin, tetracycline, and trimethoprim-sulfamethoxazole but did not correlate with increased resistance to the fluoroquinolones, rifampin, or vancomycin. These findings may be helpful to health professionals selecting empiric therapy for respiratory tract infections involving S. pneumoniae.