Open AccessFormation of hydroxyl radicals contributes to the bactericidal activity of ciprofloxacin against P seudomonas aeruginosa biofilms
Author(s) -
Jensen Peter Ø.,
Briales Alejandra,
Brochmann Rikke P.,
Wang Hengzhuang,
Kragh Kasper N.,
Kolpen Mette,
Hempel Casper,
Bjarnsholt Thomas,
Høiby Niels,
Ciofu Oana
Publication year - 2014
Publication title -
pathogens and disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.983
H-Index - 105
ISSN - 2049-632X
DOI - 10.1111/2049-632x.12120
Subject(s) - biofilm , ciprofloxacin , pseudomonas aeruginosa , microbiology and biotechnology , chemistry , antibiotics , reactive oxygen species , radical , catalase , bacteria , biology , biochemistry , oxidative stress , genetics
Antibiotic‐tolerant, biofilm‐forming P seudomonas aeruginosa has long been recognized as a major cause of chronic lung infections of cystic fibrosis patients. The mechanisms involved in the activity of antibiotics on biofilm are not completely clear. We have investigated whether the proposed induction of cytotoxic hydroxyl radicals (OH ˙ ) during antibiotic treatment of planktonically grown cells may contribute to action of the commonly used antibiotic ciprofloxacin on P . aeruginosa biofilms. For this purpose, WT PAO1, a catalase deficient Δ katA and a ciprofloxacin resistant mutant of PAO1 ( gyrA ), were grown as biofilms in microtiter plates and treated with ciprofloxacin. Formation of OH ˙ and total amount of reactive oxygen species ( ROS ) was measured and viability was estimated. Formation of OH ˙ and total ROS in PAO1 biofilms treated with ciprofloxacin was shown but higher levels were measured in Δ katA biofilms, and no ROS production was seen in the gyrA biofilms. Treatment with ciprofloxacin decreased the viability of PAO1 and Δ katA biofilms but not of gyrA biofilms. Addition of thiourea, a OH ˙ scavenger, decreased the OH ˙ levels and killing of PAO1 biofilm. Our study shows that OH ˙ is produced by P . aeruginosa biofilms treated with ciprofloxacin, which may contribute to the killing of biofilm subpopulations.