Post-antibiotic effect of ciprofloxacin on Pseudomonas aeruginosa.

The post-antibiotic effect of ciprofloxacin on five strains of Pseudomonas aeruginosa was examined. Ciprofloxacin demonstrated rapid bactericidal action at concentrations achievable in serum. After removal of the drug persistent suppression of bacterial growth followed by regrowth was observed for all strains after exposure of the organisms to various concentrations of ciprofloxacin for limited periods of time (0.25-3 h). The duration of this post-antibiotic effect increased with the concentration of the drug and duration of exposure up to a point of maximal response. This point was reached after approximately 2.2 h using a ciprofloxacin concentration 5-10 times the MIC and 1-2 h of treatment.