Sitafloxacin hydrate (DU-6859a, Gracevit), a new-generation, broad-spectrum oral fluoroquinolone that is very active against many Gram-positive, Gram-negative and anaerobic clinical isolates, including strains resistant to other fluoroquinolones, was recently approved in Japan for the treatment of respiratory and urinary tract infections. This is a new quinolone oral antibacterial to inhibit DNA replication of bacteria at the time of infection, and shows antibacterial action. Sitafloxacin is active against methicillin-resistant staphylococci, Streptococcus pneumoniae and other streptococci with reduced susceptibility to levofloxacin and other quinolones and enterococci. Sitafloxacin has also demonstrated activity against clinical isolates of Klebsiella pneumoniae (including about 67% of strains producing extended-spectrum, beta-lactamases and resistant to ciprofloxacin), Enterobacter cloacae, Pseudomonas aeruginosa with some activity against quinolone-resistant strains and Acinetobacter baumannii. The in vitro activity against anaerobes is comparable to imipenem or metronidazole. Sitafloxacin showed dual inhibitory activity against both enzymes: Streptococcus pneumoniae DNA gyrase and topoisomerase IV.