TY - JOUR

T1 - Bactericidal effect of colistin on planktonic Pseudomonas aeruginosa is independent of hydroxyl radical formation

AU - Brochmann, Rikke Prejh

AU - Toft, Anders

AU - Ciofu, Oana

AU - Briales, Alejandra

AU - Kolpen, Mette

AU - Hempel, Casper

AU - Bjarnsholt, Thomas

AU - Høiby, Niels

AU - Jensen, Peter Østrup

N1 - Copyright © 2013 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

PY - 2014

Y1 - 2014

N2 - The bactericidal effect of several major types of antibiotics has recently been demonstrated to be dependent on the formation of toxic amounts of hydroxyl radicals (OH·) resulting from oxidative stress in metabolically active cells. Since killing by the antimicrobial peptide colistin does not require bacterial metabolic activity, we tested whether the bactericidal effect of colistin depends on the formation of OH·. In Pseudomonas aeruginosa cultures, OH-mediated killing by ciprofloxacin was demonstrated by decreased bacterial survival and induction of 3'-(p-hydroxyphenyl) fluorescein (HPF) fluorescence. OH·-mediated killing by ciprofloxacin was further confirmed by rescue of cells and reduction of HPF fluorescence due to prevention of OH· accumulation by scavenging with thiourea, by chelating with dipyridyl, by decreasing metabolism as well as by anoxic growth. In contrast, no formation of OH· was seen in P. aeruginosa during killing by colistin, and prevention of OH· accumulation could not rescue P. aeruginosa from killing by colistin. These results therefore demonstrate that the bactericidal activity of colistin on P. aeruginosa is not dependent on oxidative stress. In conclusion, antimicrobial peptides that do not rely on OH· formation should be considered for treatment of Gram-negative bacteria growing at low oxygen tension such as in endobronchial mucus and paranasal sinuses in cystic fibrosis patients, in abscesses and in infectious biofilm.

AB - The bactericidal effect of several major types of antibiotics has recently been demonstrated to be dependent on the formation of toxic amounts of hydroxyl radicals (OH·) resulting from oxidative stress in metabolically active cells. Since killing by the antimicrobial peptide colistin does not require bacterial metabolic activity, we tested whether the bactericidal effect of colistin depends on the formation of OH·. In Pseudomonas aeruginosa cultures, OH-mediated killing by ciprofloxacin was demonstrated by decreased bacterial survival and induction of 3'-(p-hydroxyphenyl) fluorescein (HPF) fluorescence. OH·-mediated killing by ciprofloxacin was further confirmed by rescue of cells and reduction of HPF fluorescence due to prevention of OH· accumulation by scavenging with thiourea, by chelating with dipyridyl, by decreasing metabolism as well as by anoxic growth. In contrast, no formation of OH· was seen in P. aeruginosa during killing by colistin, and prevention of OH· accumulation could not rescue P. aeruginosa from killing by colistin. These results therefore demonstrate that the bactericidal activity of colistin on P. aeruginosa is not dependent on oxidative stress. In conclusion, antimicrobial peptides that do not rely on OH· formation should be considered for treatment of Gram-negative bacteria growing at low oxygen tension such as in endobronchial mucus and paranasal sinuses in cystic fibrosis patients, in abscesses and in infectious biofilm.

U2 - 10.1016/j.ijantimicag.2013.10.015

DO - 10.1016/j.ijantimicag.2013.10.015

M3 - Journal article

C2 - 24315789

VL - 43

SP - 140

EP - 147

JO - International Journal of Antimicrobial Agents

JF - International Journal of Antimicrobial Agents

SN - 0924-8579

IS - 2

ER -