Antibacterial activity of AM-1155 against penicillin-resistant Streptococcus pneumoniae.

AM-1155, a novel fluoroquinolone, exhibited potent activity against Streptococcus pneumoniae, including penicillin-resistant strains; the MIC90 for 48 clinical isolates was 0.25 mg/L. The antibacterial activity of AM-1155 against S. pneumoniae was higher than that of levofloxacin (MIC90 1 mg/L) and comparable with that of sparfloxacin. The MIC90s of penicillin G and erythromycin were 2 and > 4 mg/L, respectively. AM-1155 showed no cross-resistance to penicillin or erythromycin. For experimental murine pneumonia with S. pneumoniae intermediately resistant to penicillin, oral administration of AM-1155 showed efficacy higher than that of levofloxacin and equal to that of sparfloxacin. The efficacy of AM-1155 was also equal to that of subcutaneous penicillin G administration at the same dosage.