TY - JOUR

T1 - Increased bactericidal activity of colistin on Pseudomonas aeruginosa biofilms in anaerobic conditions

AU - Kolpen, Mette

AU - Appeldorff, Cecilie F.

AU - Brandt, Sarah

AU - Mousavi, Nabi

AU - Kragh, Kasper N.

AU - Aydogan, Sevtap

AU - Uppal, Haleema A.

AU - Bjarnsholt, Thomas

AU - Ciofu, Oana

AU - Hoiby, Niels

AU - Jensen, Peter Østrup

PY - 2016/2

Y1 - 2016/2

N2 - Tolerance towards antibiotics of Pseudomonas aeruginosa biofilms is recognized as a major cause of therapeutic failure of chronic lung infection in cystic fibrosis (CF) patients. This lung infection is characterized by antibiotic-tolerant biofilmsin mucus with zones of O2 depletion mainly due to polymorphonuclear eukocytic activity. In contrast to the main types of bactericidal antibiotics, it has not been possible to establish an association between the bactericidal effects of colistin and the production of detectable levels of OH˙on several strains of planktonic P. aeruginosa. Therefore, we propose that production of OH˙may not contribute significantly to the bactericidal activity of colistin on P. aeruginosa biofilm. Thus, we investigated the effect of colistin treatment on biofilm of wild-type PAO1, a catalase-deficient mutant (katA) and a colistin-resistant CF isolate cultured in microtiter plates in normoxic- or anoxic atmosphere with 1 mM nitrate. The killing of bacteria during colistin treatment was measured by CFU counts, and the OH· formation was measured by 3 -(p-hydroxylphenyl fluorescein)fluorescein (HPF) fluorescence. Validation of the assay was done by hydrogen peroxide treatment. OH· formation was undetectable in aerobic PAO1 biofilms during 3 h of colistin treatment. Interestingly, we demonstrate increasedsusceptibility of P. aeruginosa biofilms towards colistin during anaerobic conditions. In fact, the maximum enhancement of killing by anaerobic conditions exceeded 2 logs using 4 mg L−1 of colistin compared to killing at aerobic conditions.

AB - Tolerance towards antibiotics of Pseudomonas aeruginosa biofilms is recognized as a major cause of therapeutic failure of chronic lung infection in cystic fibrosis (CF) patients. This lung infection is characterized by antibiotic-tolerant biofilmsin mucus with zones of O2 depletion mainly due to polymorphonuclear eukocytic activity. In contrast to the main types of bactericidal antibiotics, it has not been possible to establish an association between the bactericidal effects of colistin and the production of detectable levels of OH˙on several strains of planktonic P. aeruginosa. Therefore, we propose that production of OH˙may not contribute significantly to the bactericidal activity of colistin on P. aeruginosa biofilm. Thus, we investigated the effect of colistin treatment on biofilm of wild-type PAO1, a catalase-deficient mutant (katA) and a colistin-resistant CF isolate cultured in microtiter plates in normoxic- or anoxic atmosphere with 1 mM nitrate. The killing of bacteria during colistin treatment was measured by CFU counts, and the OH· formation was measured by 3 -(p-hydroxylphenyl fluorescein)fluorescein (HPF) fluorescence. Validation of the assay was done by hydrogen peroxide treatment. OH· formation was undetectable in aerobic PAO1 biofilms during 3 h of colistin treatment. Interestingly, we demonstrate increasedsusceptibility of P. aeruginosa biofilms towards colistin during anaerobic conditions. In fact, the maximum enhancement of killing by anaerobic conditions exceeded 2 logs using 4 mg L−1 of colistin compared to killing at aerobic conditions.

KW - Pseudomonas aeruginosa

KW - colistin

KW - hydroxyl radicals

KW - biofilm

KW - anaerobic conditions

U2 - 10.1093/femspd/ftv086

DO - 10.1093/femspd/ftv086

M3 - Journal article

C2 - 26458402

VL - 74

JO - FEMS Immunology and Medical Microbiology

JF - FEMS Immunology and Medical Microbiology

SN - 2049-632X

IS - 1

M1 - ftv086

ER -