Comparison of oxidative stress induced by ciprofloxacin and pyoverdin in bacteria and in leukocytes to evaluate toxicity.

Oxidative stress induced by ciprofloxacin and pyoverdin, a leukotoxic pigment, was studied by comparing their effect in bacteria and leukocytes. Chemiluminescence (CL) assays with lucigenin or luminol were adapted to measure the stimuli of superoxide anion (O2 -) and other reactive species of oxygen (ROS) in bacteria. Ciprofloxacin principally induced the production of O2 - in the three species studied: Staphylococcus aureus, Enterococcus faecalis and Escherichia coli. Lucigenin CL assay showed high oxidative stress in S. aureus due to its low superoxide dismutase (SOD) activity, whereas E. coli exhibited important SOD activity, responsible for little production of O2 - in absence or presence of ciprofloxacin. Reduction of nitroblue of tetrazolium (NBT) was applied. This assay indicated that there was higher oxidative stress in S. aureus and E. faecalis than in E. coli. The comparison of oxidative stress generated in bacteria and leukocytes was used to check the selective toxicity of ciprofloxacin in comparison with pyoverdin. Ciprofloxacin did not generate significant stimuli of O2 - in neutrophils, while pyoverdin duplicated the production of O2 -. CL and NBT were useful to study the leukotoxicity of ciprofloxacin. Oxidative stress caused by the antibiotic and the leukotoxic pigment was similar in bacteria. Copyright 2003 John Wiley & Sons, Ltd.