Polarized light micrograph of cirprofloxacin drug crystals, a broad-spectrum antibiotic of the fluoroquinolone class. It is a nucleic acid synthesis inhibitor: during the proliferation phase of a bacterium it acts by inhibiting the enzymes DNA gyrase and topoisomerase IV, which are required for bacterial DNA synthesis, thereby preventing cell division, and resulting in bacterial cell death. Considered the reference quinolone antibiotic, ciprofloxacin is used mainly to treat infections of the gastrointestinal and genitourinary tract, as well as respiratory tract infections. It is also active against typhoid fever, some sexually transmitted diseases, infectious diarrhea, septicemia, and inhalational anthrax, and is used as an antineoplastic agent. Field of view size: 0.30 x 0.45 mm (0.012 x 0.018 in)