Inhibitory activity of ciprofloxacin on the decatenation reaction of topoisomerase IV from S. pneumoniae C3LN4. Lane 1, drug-free control; lanes 2 to 8, ciprofloxacin at 2, 4, 6, 8, 10, 12, and 14 μg per ml, respectively; kDNA, catenated kinetoplast DNA; monomer, decatenated monomer DNA.