PD 131628 is a new aminopyrrolidine-substituted fluorocyclopropyl naphthyridine quinolone which possesses high in vitro activity against a wide spectrum of bacterial species. The MICs for greater-than-or-equal-to 90% of strains were 0.125 to 0.25-mu-g/ml for staphylococci, Streptococcus pyogenes, and S. pneumoniae; 0.5-n-mu-g/ml for S. agalactiae and Enterococcus faecalis; 0.125-mu-g/ml for members of the family Enterobacteriaceae and Acinetobacter supp.; 0.5-mu-g/ml for Pseudomonas aeruginosa; and less-than-or-equal-to 0.03-mu-g/ml for Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and Neisseria gonorrhoeae. In these in vitro comparisons with ciprofloxacin, PD 131628 is more active against gram-positve organisms, approximately equivalent against gram-negative organisms, and, like most other quinolones, relatively inactive against gram-negative anaerobes. In most instances, the in vitro potency of PD 131628 exceeded those of widely used compounds: ciprofloxacin, imipenem, ampicillin, penicillin G, oxacillin, cefazolin, ceftazidime, cefoxitin, cefsulodin, aztreonam, piperacillin, amikacin, spectinomycin, doxycyline, erythromycin, metronidazole, and vancomycin.
