WS02.6 Increased bactericidal activity of colistin on Pseudomonas aeruginosa biofilms in anaerobic conditions

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• 作者：M. Kolpen^a ; ^b ; C.F. Appeldorff^b ; S. Brandt^b ; N. Mousavi^b ; K.N. Kragh^b ; ^c ; T. Bjarnsholt^b ; ^c ; O. Ciofu^a ; N. Hø ; iby^a ; ^b ; P.Ø ; . Jensen^b
• 刊名：Journal of Cystic Fibrosis
• 出版年：2015
• 出版时间：June 2015
• 年：2015
• 卷：14
• 期：supp_S1
• 页码：S4
• 全文大小：73 K

文摘

Tolerance towards antibiotics of Pseudomonas aeruginosa biofilms is recognized as major cause of therapeutic failure of chronic lung infection in cystic fibrosis patients. The infection is characterized by antibiotic-tolerant biofilms in mucus with zones of oxygen (O₂) depletion mainly due to polymorphonuclear leukocytic activity. In contrast to other bactericidal antibiotics, the bactericidal effect of colistin on planktonic P. aeruginosa does not depend on the formation of cytotoxic amounts of hydroxyl radicals (OH^•) suggesting the activity of colistin is independent of the presence of O₂. Therefore we investigated biofilm cultures of wildtype PAO1, catalase deficient mutant (ΔkatA) and colistin resistant CF isolate grown in microtiter plates in normoxic- or anoxic atmosphere with 1 mM nitrate for 1 or 3 days before 3 hours of colistin treatment. The killing of bacteria after colistin treatment was measured by CFU counts and the OH^• formation was measured by induction of 3'-(p-hydroxyphenyl) fluorescein (HPF) fluorescence. Validation of the assay was done by hydrogenperoxide treatment.

Aerobic colistin treatment did not induce HPF fluorescence in any of the three strains and catalase deficiency was not associated with increased susceptibility, indicating that colistin acts independently of OH^• formation. We demonstrated increased susceptibility of PAO1 biofilms towards colistin during anaerobic conditions. The maximum enhancement of killing by anaerobic conditions exceeded 4 logs using 8 mg/L of colistin compared to killing at aerobic conditions.

We highly recommend considering colistin treatment of biofilms in the anaerobic zones of CF mucus and paranasal sinuses.