Antimicrobial activity of gatifloxacin (AM-1155, CG5501), and four other fluoroquinolones tested against 2,284 recent clinical strains of Streptococcus pneumoniae from Europe, Latin America, Canada, and the United States

The newer fluoroquinolones generally have greater potency against Gram-positive cocci including Streptococcus pneumoniae. In this study, we report the activity of gatifloxacin (formerly AM-1155 or CG5501) compared with penicillin, erythromycin, and four other peer drugs, tested against 2284 strains isolated in North America (Canada and United States), Latin America (six nations), and Europe in 1997. Reference broth microdilution methods were used and results were interpreted by consensus standards. Gatifloxacin demonstrated uniform potency against pneumococci across all monitored geographic areas (MIC90, 0.5 mu g/mL; greater than or equal to 99.6% of strains inhibited at less than or equal to 1 mu g/mL). This activity was comparable to trovafloxacin (MIC90, 0.5 mu g/mL) and sparfloxacin (MIC90, 0.5 mu g/mL) and two- to four-fold greater than that of ciprofloxacin or levofloxacin. The most resistant strains to the fluoroquinolones has mutations in both par C (Ser79-->Phe) and gyr A (Ser83-->Lys or Phe). Penicillin resistance (MIC, greater than or equal to 0.12 mu g/mL) rates varied from 27.6% in Europe to 55.7% in Latin America. Macrolide resistance was greatest in Europe and the United States. Gatifloxacin appears to be a promising new fluoroquinolone for clinical use in respiratory tract infections commonly caused by S. pneumoniae. (C) 1999 Elsevier Science Inc.