Sitafloxacin (DU6859a) monohydrate is a potent, orally active fluoroquinolone antibiotic. Sitafloxacin monohydrate shows antichlamydial activity and antibacterial activities against a broad range of gram-positive and gram-negative bacteria, including anaerobic bacteria, as well as against atypical pathogens. Sitafloxacin monohydrate can be used for the research of respiratory tract infection and urinary tract infection.