Killing kinetics of four quinolones against gram-positive cocci

Killing kinetics of four fluoroquinolones against Staphylococcus species were determined during the first 5 h of incubation in the presence of drug concentrations ranging from the MIC to 1,024 micrograms/ml. Additionally, the relationship between killing rate and drug concentration was established. Sparfloxacin and temafloxacin were the most active quinolones assayed with greater lethal rates than ciprofloxacin and norfloxacin. The relation was biphasic with a decrease of at least 1 log10 c.f.u./ml at high drug concentrations with respect to that obtained at the optimal bactericidal concentration for all quinolone-microorganism combinations tested.