scholarly journals Antibacterial Mechanism of Action of Arylamide Foldamers

2011 ◽  
Vol 55 (11) ◽  
pp. 5043-5053 ◽  
Author(s):  
Bruk Mensa ◽  
Yong Ho Kim ◽  
Sungwook Choi ◽  
Richard Scott ◽  
Gregory A. Caputo ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mechanism Of Action ◽  
Morphological Changes ◽  
Transcriptional Profiling ◽  
Polymyxin B ◽  
Content Type ◽  
Oxidative Stresses ◽  
Bacterial Cell Death ◽  
Arylamide Foldamers ◽  
Time Required

ABSTRACTSmall arylamide foldamers designed to mimic the amphiphilic nature of antimicrobial peptides (AMPs) have shown potent bactericidal activity against both Gram-negative and Gram-positive strains without many of the drawbacks of natural AMPs. These foldamers were shown to cause large changes in the permeability of the outer membrane ofEscherichia coli. They cause more limited permeabilization of the inner membrane which reaches critical levels corresponding with the time required to bring about bacterial cell death. Transcriptional profiling ofE. colitreated with sublethal concentrations of the arylamides showed induction of genes related to membrane and oxidative stresses, with some overlap with the effects observed for polymyxin B. Protein secretion into the periplasm and the outer membrane is also compromised, possibly contributing to the lethality of the arylamide compounds. The induction of membrane stress response regulons such asrcscoupled with morphological changes at the membrane observed by electron microscopy suggests that the activity of the arylamides at the membrane represents a significant contribution to their mechanism of action.

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 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 The Antimicrobial Mechanism of Action of Epsilon-Poly-l-Lysine

2014 ◽  
Vol 80 (24) ◽  
pp. 7758-7770 ◽  
Author(s):  
Morten Hyldgaard ◽  
Tina Mygind ◽  
Brian S. Vad ◽  
Marcel Stenvang ◽  
Daniel E. Otzen ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Mechanism Of Action ◽  
Cell Morphology ◽  
Morphological Changes ◽  
Divalent Cations ◽  
Membrane Integrity ◽  
Model Organisms ◽  
Microscopy Imaging ◽  
Content Type ◽  
E Coli

ABSTRACTEpsilon-poly-l-lysine (ε-PL) is a natural antimicrobial cationic peptide which is generally regarded as safe (GRAS) as a food preservative. Although its antimicrobial activity is well documented, its mechanism of action is only vaguely described. The aim of this study was to clarify ε-PL's mechanism of action usingEscherichia coliandListeria innocuaas model organisms. We examined ε-PL's effect on cell morphology and membrane integrity and used an array ofE. colideletion mutants to study how specific outer membrane components affected the action of ε-PL. We furthermore studied its interaction with lipid bilayers using membrane models.In vitrocell studies indicated that divalent cations and the heptose I and II phosphate groups in the lipopolysaccharide layer ofE. coliare critical for ε-PL's binding efficiency. ε-PL removed the lipopolysaccharide layer and affected cell morphology ofE. coli, whileL. innocuaunderwent minor morphological changes. Propidium iodide staining showed that ε-PL permeabilized the cytoplasmic membrane in both species, indicating the membrane as the site of attack. We compared the interaction with neutral or negatively charged membrane systems and showed that the interaction with ε-PL relied on negative charges on the membrane. Suspended membrane vesicles were disrupted by ε-PL, and a detergent-like disruption ofE. colimembrane was confirmed by atomic force microscopy imaging of supported lipid bilayers. We hypothesize that ε-PL destabilizes membranes in a carpet-like mechanism by interacting with negatively charged phospholipid head groups, which displace divalent cations and enforce a negative curvature folding on membranes that leads to formation of vesicles/micelles.

scholarly journals An Outer Membrane Protein Involved in the Uptake of Glucose Is Essential for Cytophaga hutchinsonii Cellulose Utilization

2016 ◽  
Vol 82 (6) ◽  
pp. 1933-1944 ◽  
Author(s):  
Hong Zhou ◽  
Xia Wang ◽  
Tengteng Yang ◽  
Weixin Zhang ◽  
Guanjun Chen ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Cellulose Degradation ◽  
Expression Profiles ◽  
Transcriptional Profiling ◽  
Hydrolysis Product ◽  
Transcriptional Responses ◽  
Content Type ◽  
Cytophaga Hutchinsonii

ABSTRACTCytophaga hutchinsoniispecializes in cellulose digestion by employing a collection of novel cell-associated proteins. Here, we identified a novel gene locus, CHU_1276, that is essential forC. hutchinsoniicellulose utilization. Disruption of CHU_1276 inC. hutchinsoniiresulted in complete deficiency in cellulose degradation, as well as compromised assimilation of cellobiose or glucose at a low concentration. Further analysis showed that CHU_1276 was an outer membrane protein that could be induced by cellulose and low concentrations of glucose. Transcriptional profiling revealed that CHU_1276 exerted a profound effect on the genome-wide response to both glucose and Avicel and that the mutant lacking CHU_1276 displayed expression profiles very different from those of the wild-type strain under different culture conditions. Specifically, comparison of their transcriptional responses to cellulose led to the identification of a gene set potentially regulated by CHU_1276. These results suggest that CHU_1276 plays an essential role in cellulose utilization, probably by coordinating the extracellular hydrolysis of cellulose substrate with the intracellular uptake of the hydrolysis product inC. hutchinsonii.

scholarly journals New Polymyxin B Dosing Strategies To Fortify Old Allies in the War against KPC-2-Producing Klebsiella pneumoniae

2017 ◽  
Vol 61 (4) ◽  
Author(s):  
Zackery P. Bulman ◽  
Michael J. Satlin ◽  
Liang Chen ◽  
Barry N. Kreiswirth ◽  
Beom Soo Shin ◽  
...  
Keyword(s):  
Single Dose ◽  
Klebsiella Pneumoniae ◽  
Polymyxin B ◽  
Infection Model ◽  
Triple Combination ◽  
Content Type ◽  
High Single Dose ◽  
Dosing Strategies ◽  
Time Required ◽  
Time Kill

ABSTRACT Pharmacodynamics of a polymyxin B, meropenem, and rifampin triple combination were examined against Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) ST258. In time-kill experiments against three KPC-Kp isolates, triple combination generated 8.14, 8.19, and 8.29 log10 CFU/ml reductions within 24 h. In the hollow-fiber infection model, the triple combination caused maximal killing of 5.16 log10 CFU/ml at 78 h and the time required for regrowth was more than doubled versus the 2-drug combinations. Remarkably, combinations with a high single-dose polymyxin B burst plus rifampin preserved KPC-Kp polymyxin susceptibility (MIC240 h = 0.5 mg/liter) versus the same combination with traditionally dosed polymyxin B, where resistance was amplified (MIC240 h = 32 mg/liter).

scholarly journals Brucella abortus and Its Closest Phylogenetic Relative, Ochrobactrum spp., Differ in Outer Membrane Permeability and Cationic Peptide Resistance

2000 ◽  
Vol 68 (6) ◽  
pp. 3210-3218 ◽  
Author(s):  
J. Velasco ◽  
J. A. Bengoechea ◽  
K. Brandenburg ◽  
B. Lindner ◽  
U. Seydel ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Outer Membrane ◽  
Brucella Abortus ◽  
Morphological Changes ◽  
Acyl Chain ◽  
Polymyxin B ◽  
E Coli ◽  
Structural Rigidity ◽  
Live Bacteria ◽  
Outer Membrane Permeability

ABSTRACT The outer membrane (OM) of the intracellular parasiteBrucella abortus is permeable to hydrophobic probes and resistant to destabilization by polycationic peptides and EDTA. The significance of these unusual properties was investigated in a comparative study with the opportunistic pathogens of the genusOchrobactrum, the closest known Brucellarelative. Ochrobactrum spp. OMs were impermeable to hydrophobic probes and sensitive to polymyxin B but resistant to EDTA. These properties were traced to lipopolysaccharide (LPS) because (i) insertion of B. abortus LPS, but not of Escherichia coli LPS, into Ochrobactrum OM increased its permeability; (ii) permeability and polymyxin B binding measured with LPS aggregates paralleled the results with live bacteria; and (iii) the predicted intermediate results were obtained with B. abortus-Ochrobactrum anthropi and E. coli-O. anthropiLPS hybrid aggregates. Although Ochrobactrum was sensitive to polymyxin, self-promoted uptake and bacterial lysis occurred without OM morphological changes, suggesting an unusual OM structural rigidity.Ochrobactrum and B. abortus LPSs showed no differences in phosphate, qualitative fatty acid composition, or acyl chain fluidity. However, Ochrobactrum LPS, but not B. abortus LPS, contained galacturonic acid. B. abortusand Ochrobactrum smooth LPS aggregates had similar size and zeta potential (−12 to −15 mV). Upon saturation with polymyxin, zeta potential became positive (1 mV) for Ochrobactrum smooth LPS while remaining negative (−5 mV) for B. abortus smooth LPS, suggesting hindered access to inner targets. These results show that although Ochrobactrum and Brucella share a basic OM pattern, subtle modifications in LPS core cause markedly different OM properties, possibly reflecting the adaptive evolution ofB. abortus to pathogenicity.

scholarly journals Phosphate Groups of Lipid A Are Essential for Salmonella enterica Serovar Typhimurium Virulence and Affect Innate and Adaptive Immunity

2012 ◽  
Vol 80 (9) ◽  
pp. 3215-3224 ◽  
Author(s):  
Qingke Kong ◽  
David A. Six ◽  
Qing Liu ◽  
Lillian Gu ◽  
Shifeng Wang ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Adaptive Immunity ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Outer Membrane Proteins ◽  
Polymyxin B ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Phosphate Groups

ABSTRACTLipid A is a key component of the outer membrane of Gram-negative bacteria and stimulates proinflammatory responses via the Toll-like receptor 4 (TLR4)-MD2-CD14 pathway. Its endotoxic activity depends on the number and length of acyl chains and its phosphorylation state. InSalmonella entericaserovar Typhimurium, removal of the secondary laurate or myristate chain in lipid A results in bacterial attenuation and growth defectsin vitro. However, the roles of the two lipid A phosphate groups in bacterial virulence and immunogenicity remain unknown. Here, we used anS. TyphimuriummsbB pagL pagP lpxRmutant, carrying penta-acylated lipid A, as the parent strain to construct a series of mutants synthesizing 1-dephosphorylated, 4′-dephosphorylated, or nonphosphorylated penta-acylated lipid A. Dephosphorylated mutants exhibited increased sensitivity to deoxycholate and showed increased resistance to polymyxin B. Removal of both phosphate groups severely attenuated the mutants when administered orally to BALB/c mice, but the mutants colonized the lymphatic tissues and were sufficiently immunogenic to protect the host from challenge with wild-typeS. Typhimurium. Mice receivingS. Typhimurium with 1-dephosphorylated or nonphosphorylated penta-acylated lipid A exhibited reduced levels of cytokines. Attenuated and dephosphorylatedSalmonellavaccines were able to induce adaptive immunity against heterologous (PspA ofStreptococcus pneumoniae) and homologous antigens (lipopolysaccharide [LPS] and outer membrane proteins [OMPs]).

scholarly journals The Monoterpene Carvacrol Generates Endoplasmic Reticulum Stress in the Pathogenic Fungus Candida albicans

2015 ◽  
Vol 59 (8) ◽  
pp. 4584-4592 ◽  
Author(s):  
Julien Chaillot ◽  
Faiza Tebbji ◽  
Adnane Remmal ◽  
Charlie Boone ◽  
Grant W. Brown ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Candida Albicans ◽  
Antifungal Activity ◽  
Mechanism Of Action ◽  
Pathogenic Fungus ◽  
Transcriptional Profiling ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Transcriptional Signature ◽  
The Unfolded Protein Response

ABSTRACTThe monoterpene carvacrol, the major component of oregano and thyme oils, is known to exert potent antifungal activity against the pathogenic yeastCandida albicans. This monoterpene has been the subject of a considerable number of investigations that uncovered extensive pharmacological properties, including antifungal and antibacterial effects. However, its mechanism of action remains elusive. Here, we used integrative chemogenomic approaches, including genome-scale chemical-genetic and transcriptional profiling, to uncover the mechanism of action of carvacrol associated with its antifungal property. Our results clearly demonstrated that fungal cells require the unfolded protein response (UPR) signaling pathway to resist carvacrol. The mutants most sensitive to carvacrol in our genome-wide competitive fitness assay in the yeastSaccharomyces cerevisiaeexpressed mutations of the transcription factor Hac1 and the endonuclease Ire1, which is required for Hac1 activation by removing a nonconventional intron from the 3′ region ofHAC1mRNA. Confocal fluorescence live-cell imaging revealed that carvacrol affects the morphology and the integrity of the endoplasmic reticulum (ER). Transcriptional profiling of pathogenic yeastC. albicanscells treated with carvacrol demonstrated a bona fide UPR transcriptional signature. Ire1 activity detected by the splicing ofHAC1mRNA inC. albicanswas activated by carvacrol. Furthermore, carvacrol was found to potentiate antifungal activity of the echinocandin antifungal caspofungin and UPR inducers dithiothreitol and tunicamycin againstC. albicans. This comprehensive chemogenomic investigation demonstrated that carvacrol exerts its antifungal activity by altering ER integrity, leading to ER stress and the activation of the UPR to restore protein-folding homeostasis.

Sign in / Sign up

Export Citation Format

Share Document