Isolation of lipopolysaccharides and the effect of Polymyxin B on the outer membrane of Corynebacterium autotrophicum

1978 ◽  
Vol 118 (1) ◽  
pp. 67-69 ◽  
Author(s):  
J�rgen Wiegel ◽  
Frank Mayer
Keyword(s):  
Outer Membrane ◽  
Polymyxin B ◽  
Corynebacterium Autotrophicum

scholarly journals Antibiotic-Mediated Modulations of Outer Membrane Vesicles in Enterohemorrhagic Escherichia coli O104:H4 and O157:H7

2017 ◽  
Vol 61 (9) ◽  
Author(s):  
Andreas Bauwens ◽  
Lisa Kunsmann ◽  
Helge Karch ◽  
Alexander Mellmann ◽  
Martina Bielaszewska
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Shiga Toxin ◽  
Membrane Vesicles ◽  
Polymyxin B ◽  
Outer Membrane Vesicles ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
E Coli ◽  
Major Virulence Factor

ABSTRACT Ciprofloxacin, meropenem, fosfomycin, and polymyxin B strongly increase production of outer membrane vesicles (OMVs) in Escherichia coli O104:H4 and O157:H7. Ciprofloxacin also upregulates OMV-associated Shiga toxin 2a, the major virulence factor of these pathogens, whereas the other antibiotics increase OMV production without the toxin. These two effects might worsen the clinical outcome of infections caused by Shiga toxin-producing E. coli. Our data support the existing recommendations to avoid antibiotics for treatment of these infections.

scholarly journals Lipidomic Analysis of the Outer Membrane Vesicles from Paired Polymyxin-Susceptible and -Resistant Klebsiella pneumoniae Clinical Isolates

2018 ◽  
Vol 19 (8) ◽  
pp. 2356 ◽  
Author(s):  
Raad Jasim ◽  
Mei-Ling Han ◽  
Yan Zhu ◽  
Xiaohan Hu ◽  
Maytham Hussein ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Membrane Vesicles ◽  
Average Diameter ◽  
Polymyxin B ◽  
Outer Membrane Vesicles ◽  
Resistant Isolate ◽  
Average Particle ◽  
Lipid Species ◽  
The Impact

Gram-negative bacteria produce outer membrane vesicles (OMVs) as delivery vehicles for nefarious bacterial cargo such as virulence factors, which are antibiotic resistance determinants. This study aimed to investigate the impact of polymyxin B treatment on the OMV lipidome from paired polymyxin-susceptible and -resistant Klebsiella pneumoniae isolates. K. pneumoniae ATCC 700721 was employed as a reference strain in addition to two clinical strains, K. pneumoniae FADDI-KP069 and K. pneumoniae BM3. Polymyxin B treatment of the polymyxin-susceptible strains resulted in a marked reduction in the glycerophospholipid, fatty acid, lysoglycerophosphate and sphingolipid content of their OMVs. Conversely, the polymyxin-resistant strains expressed OMVs richer in all of these lipid species, both intrinsically and increasingly under polymyxin treatment. The average diameter of the OMVs derived from the K. pneumoniae ATCC 700721 polymyxin-susceptible isolate, measured by dynamic light scattering measurements, was ~90.6 nm, whereas the average diameter of the OMVs isolated from the paired polymyxin-resistant isolate was ~141 nm. Polymyxin B treatment (2 mg/L) of the K. pneumoniae ATCC 700721 cells resulted in the production of OMVs with a larger average particle size in both the susceptible (average diameter ~124 nm) and resistant (average diameter ~154 nm) strains. In light of the above, we hypothesize that outer membrane remodelling associated with polymyxin resistance in K. pneumoniae may involve fortifying the membrane structure with increased glycerophospholipids, fatty acids, lysoglycerophosphates and sphingolipids. Putatively, these changes serve to make the outer membrane and OMVs more impervious to polymyxin attack.

scholarly journals Outer Membrane Interaction Kinetics of New Polymyxin B Analogs in Gram-Negative Bacilli

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Noushin Akhoundsadegh ◽  
Corrie R. Belanger ◽  
Robert E. W. Hancock
Keyword(s):  
Outer Membrane ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Intact Cells ◽  
Membrane Interaction ◽  
Gram Negative ◽  
Content Type ◽  
Interaction Kinetics ◽  
Hill Numbers ◽  
Multiple Strains

ABSTRACT Infections caused by drug-resistant Gram-negative bacilli are a severe global health threat, limiting effective drug choices for treatment. In this study, polymyxin analogs designed to have reduced nephrotoxicity, direct activity, and potentiating activity were assessed for inhibition and outer membrane interaction kinetics against wild-type (WT) and polymyxin or multidrug-resistant (MDR) Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. In MIC assays, two polymyxin B (PMB) analogs (SPR1205 and SPR206) and a polymyxin E analog (SPR946), with shortened peptide side chains and branched aminobutyryl N termini, exhibited promising activity compared with PMB and previously tested control polymyxin analogs SPR741 and polymyxin B nonapeptide (PMBN). Using dansyl-polymyxin (DPX) binding to assess the affinity of interaction with lipopolysaccharide (LPS), purified or in the context of intact cells, SPR206 exhibited similar affinities to PMB but higher affinities than the other SPR analogs. Outer membrane permeabilization measured by the 1-N-phenyl-napthylamine (NPN) assay did not differ significantly between the polymyxin analogs. Moreover, Hill numbers were greater than 1 for most of the compounds tested on E. coli and P. aeruginosa strains which indicates that the disruption of the outer membrane by one molecule of compound cooperatively enhances the subsequent interactions of other molecules against WT and MDR strains. The high activity demonstrated by SPR206 as well as its ability to displace LPS and permeabilize the outer membrane of multiple strains of Gram-negative bacilli while showing cooperative potential with other membrane disrupting compounds supports further research with this polymyxin analog.

scholarly journals Structure and Association of Human Lactoferrin Peptides with Escherichia coli Lipopolysaccharide

2004 ◽  
Vol 48 (6) ◽  
pp. 2190-2198 ◽  
Author(s):  
Daniel S. Chapple ◽  
Rohanah Hussain ◽  
Christopher L. Joannou ◽  
Robert E. W. Hancock ◽  
Edward Odell ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Bactericidal Activity ◽  
Membrane Surface ◽  
Polymyxin B ◽  
Cd Spectroscopy ◽  
Time Dependent ◽  
Human Lactoferrin ◽  
Lag Phase ◽  
Ligand Interaction

ABSTRACT An 11-amino-acid amphipathic synthetic peptide homologous to a helical region on helix 1 of human lactoferrin HLP-2 exhibited bactericidal activity against Escherichia coli serotype O111, whereas an analogue synthesized with Pro substituted for Met, HLP-6, had greatly reduced antimicrobial activity. The bactericidal activity of HLP-2 was 10-fold greater than that of HLP-6 in both buffer and growth medium by time-kill assays. These assays also showed a pronounced lag phase that was both concentration and time dependent and that was far greater for HLP-2 than for HLP-6. Both peptides, however, were shown to be equally efficient in destabilizing the outer membrane when the hydrophobic probe 1-N-phenylnaphthylamine was used and to have the same lipopolysaccharide (LPS) binding affinity, as shown by polymyxin B displacement. Circular dichroism (CD) spectroscopy was used to study the structure and the organization of the peptides in solution and upon interaction with E. coli LPS. In the presence of LPS, HLP-2 and HLP-6 were found to bind and adopt a β-strand conformation rather than an α-helix, as shown by nonimmobilized ligand interaction assay-CD spectroscopy. Furthermore, this assay was used to show that there is a time-dependent association of peptide that results in an ordered formation of peptide aggregates. The rate of interpeptide association was far greater in HLP-2 LPS than in HLP-6 LPS, which was consistent with the lag phase observed on the killing curves. These results allow us to propose a mechanism by which HLP-2 folds and self-assembles at the outer membrane surface before exerting its activity.

scholarly journals The Vibrio cholerae ToxR-Regulated Porin OmpU Confers Resistance to Antimicrobial Peptides

2004 ◽  
Vol 72 (6) ◽  
pp. 3577-3583 ◽  
Author(s):  
Jyoti Mathur ◽  
Matthew K. Waldor
Keyword(s):  
Antimicrobial Peptides ◽  
Outer Membrane ◽  
Vibrio Cholerae ◽  
Surface Protein ◽  
Polymyxin B ◽  
Common Mechanism ◽  
Antimicrobial Protein ◽  
Wild Type ◽  
Human Gastrointestinal Tract ◽  
Serovar Typhimurium

ABSTRACT BPI (bactericidal/permeability-increasing) is a potent antimicrobial protein that was recently reported to be expressed as a surface protein on human gastrointestinal tract epithelial cells. In this study, we investigated the resistance of Vibrio cholerae, a small-bowel pathogen that causes cholera, to a BPI-derived peptide, P2. Unlike in Escherichia coli and Salmonella enterica serovar Typhimurium, resistance to P2 in V. cholerae was not dependent on the BipA GTPase. Instead, we found that ToxR, the master regulator of V. cholerae pathogenicity, controlled resistance to P2 by regulating the production of the outer membrane protein OmpU. Both toxR and ompU mutants were at least 100-fold more sensitive to P2 than were wild-type cells. OmpU also conferred resistance to polymyxin B sulfate, suggesting that this porin may impart resistance to cationic antibacterial proteins via a common mechanism. Studies of stationary-phase cells revealed that the ToxR-repressed porin OmpT may also contribute to P2 resistance. Finally, although the mechanism of porin-mediated resistance to antimicrobial peptides remains elusive, our data suggest that the BPI peptide sensitivity of OmpU-deficient V. cholerae is not attributable to a generally defective outer membrane.

scholarly journals N1-Benzofused Modification of Fluoroquinolones Reduces Activity Against Gram- Negative Bacteria

2019 ◽  
Author(s):  
Mark Laws ◽  
Charlotte Hind ◽  
Andrea Favaron ◽  
Shirin Jamshidi ◽  
J Mark Sutton ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Dna Gyrase ◽  
Polymyxin B ◽  
Membrane Penetration ◽  
Gram Negative ◽  
New Information ◽  
A Cell ◽  
Modelling Techniques ◽  
Free Environment ◽  
Solubility Profiles

<p>The fluoroquinolone class of antibiotics have a well-established structure-activity relationship (SAR) and a long history in the clinic, but the effect of electron-rich benzofused substituents at the N1 position remains poorly explored. Groups at this position are part of the topoisomerase-DNA binding complex and form a hydrophobic interaction with the major groove of DNA. Molecular modelling techniques were employed to select benzofused substituents that were shown to enhance this interaction of fluoroquinolones for the DNA gyrase target. Seven N1-modified fluoroquinolones were synthesised and tested against a panel of Gram-negative pathogens to determine minimum inhibitory concentration (MIC) values. Gram-negative outer membrane penetration was investigated using the membrane permeabiliser polymyxin B nonapeptide (PMBN) and the target affinity of representative compound <b>6e</b> was determined in a cell-free environment. A correlation between N1 substituent hydrophobicity and activity was observed across the MIC panel, with compound activity decreasing with increased hydrophobicity. Those compounds with highest hydrophobicity were inactive due to poor solubility profiles whereas compounds with intermediate hydrophobicity were inactive due to impaired outer membrane penetration and reduced inhibition for the DNA gyrase target, the latter in contrast to modelling predictions. This study adds new information to the fluoroquinolone SAR and suggests limited utility of large hydrophobic substitution at the N1 position of fluoroquinolones.</p>

scholarly journals Potentiation of Antibiotics against Gram-Negative Bacteria by Polymyxin B Analogue SPR741 from Unique Perturbation of the Outer Membrane

2019 ◽  
Vol 6 (6) ◽  
pp. 1405-1412 ◽  
Author(s):  
Shawn French ◽  
Maya Farha ◽  
Michael J. Ellis ◽  
Zaid Sameer ◽  
Jean-Philippe Côté ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Polymyxin B ◽  
Gram Negative Bacteria ◽  
Gram Negative
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