Interactions of polymyxin B with lipopolysaccharide-containing membranes.

Alice Goode,Vivien Yeh,Boyan B Bonev

doi:10.1039/d1fd00036e

Abstract

Bacterial resistance to antibiotics constantly remodels the battlefront between infections and antibiotic therapy. Polymyxin B, a cationic peptide with an anti-Gram-negative spectrum of activity is re-entering use as a last resort measure and as an adjuvant. We use fluorescence dequenching to investigate the role of the rough chemotype bacterial lipopolysaccharide from E. coli BL21 as a molecular facilitator of membrane disruption by LPS. The minimal polymyxin B/lipid ratio required for leakage onset increased from 5.9 × 10−4 to 1.9 × 10−7 in the presence of rLPS. We confirm polymyxin B activity against E. coli BL21 by the agar diffusion method and determined a MIC of 291 μg ml−1. Changes in lipid membrane stability and dynamics in response to polymyxin and the role of LPS are investigated by 31P NMR and high resolution 31P MAS NMR relaxation is used to monitor selective molecular interactions between polymyxin B and rLPS within bilayer lipid membranes. We observe a strong facilitating effect from rLPS on the membrane lytic properties of polymyxin B and a specific, pyrophosphate-mediated process of molecular recognition of LPS by polymyxin B.

Highlights

Bacterial infections remain the primary cause of morbidity and mortality in humans despite the success of antibiotic chemotherapy
To investigate the role LPS plays as a receptor for polymyxin, we used a dye release assay, in which CF-loaded large unilamellar vesicles (LUV) of DOPC without or with E. coli Rough chemotype lipopolysaccharide (rLPS) were incubated with increasing amounts of polymyxin B
Leakage onset in pure DOPC liposomes was observed at a polymyxin/DOPC ratio of 5.9 Â 10À4, while the presence of rLPS reduced this to 1.9 Â 10À7

Summary

Introduction

Bacterial infections remain the primary cause of morbidity and mortality in humans despite the success of antibiotic chemotherapy. To investigate the role LPS plays as a receptor for polymyxin, we used a dye release assay, in which CF-loaded large unilamellar vesicles (LUV) of DOPC without or with E. coli rLPS were incubated with increasing amounts of polymyxin B.

Results

Conclusion