Light effect and reactive oxygen species in the action of ciprofloxacin on Staphylococcus aureus

BECERRA MC; SARMIENTO M; ARGÜELLO GA; ALBESA I

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY

Elsevier Science

Año: 2004 vol. 76 p. 13 - 18

1011-1344

Oxygen consumption by Staphylococcus aureus ATCC 29213 sensitive to ciprofloxacin was determined with an oxygen selective electrode. Increase in the O2 consumption was observed with 0.45 µg/mL ciprofloxacin while higher concentrations gave rise to a reduction of O2 consumption. Resistant S.aureus strain did not show increase of O2 consumption in presence of ciprofloxacin. Nitro Blue Tetrazolium assay showed that production of reactive oxygen species (ROS) increased intracellularly in sensitive bacteria incubated with this antibiotic. The exposition to UV light (360 nm) augmented the intracellular oxidative stress of S.aureus and provoked increment of ROS in extracellular media. Generation of singlet oxygen O2 (1Dg) in S.aureus was measured by means of oxidation of methionine. The absorbance of methionine was monitored at 215 nm and a clear decrease was detected when sensitive S.aureus was stressed with ciprofloxacin. Sodium azide and 2,5-dimethylfuran were used to reinforce the evidence of O2 (1Dg) generation during oxidative stress. Assays with methionine and 2,5-dimethylfuran demonstrated that resistant S.aureus did not increase the production of O2 (1Dg) in the presence of antibiotic. DNA oxidation was investigated in presence of O2 (1Dg) generated by laser excitation of perinaphthenone and subsequent energy transfer. Deactivation of O2 (1Dg) by reaction with DNA of sensitive and resistant bacteria was observed. According to the results obtained, the effect of ciprofloxacin in S.aureus led to an increment of O2 (1Dg) generating oxidative stress in the bacteria.