In vitro antibacterial activities of PD 131628, a new 1,8-naphthyridine anti-infective agent

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 microgram/ml for staphylococci, Streptococcus pyogenes, and S. pneumoniae; 0.5 micrograms/ml for S. agalactiae and Enterococcus faecalis; 0.125 micrograms/ml for members of the family Enterobacteriaceae and Acinetobacter spp.; 0.5 micrograms/ml for Pseudomonas aeruginosa; and less than or equal to 0.03 micrograms/ml for Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and Neisseria gonorrhoeae. In these in vitro comparisons with ciprofloxacin, PD 131628 is more active against gram-positive 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, doxycycline, erythromycin, metronidazole, and vancomycin.