In vitro and in vivo antibacterial activities of T-3262, a new fluoroquinolone

T-3262, a new fluoroquinolone, showed a broad spectrum of activity against gram-positive and gram-negative bacteria. T-3262 had most potent activity against gram-positive cocci, such as Staphylococcus, Streptococcus, and Enterococcus spp. The MICs of T-3262 for 90% of strains tested were between 0.05 and 1.56 micrograms/ml. Against members of the family Enterobacteriaceae and Pseudomonas aeruginosa, the activities of T-3262 were almost equal to those of ciprofloxacin. Obligate anaerobes were also susceptible to T-3262. T-3262 was bactericidal for one strain each of Staphylococcus aureus, Escherichia coli, and P. aeruginosa at concentrations near its MIC; and fluoroquinolones, including T-3262, inhibited DNA gyrase activity at low concentrations. The 50% effective dose of T-3262 after oral administration against systemic infections with S. aureus in mice was about 6 times lower than that of ofloxacin and about 20 times lower than that of norfloxacin.