Gemifloxacin mesylate (SB-265805S; LB-20304a) is an orally active broad-spectrum quinolone antibacterial antibiotic . Gemifloxacin mesylate inhibits DNA synthesis by inhibiting DNA gyrase and Topoisomerase IV activities. Gemifloxacin mesylate has potent antibacterial activities against gram-positive bacteria in vitro efficacy study, particularly Streptococci and Staphylococci . Gemifloxacin mesylate has been used in the research of respiratory tract infections.