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 Novel Engineered Peptides of a Phage Lysin as Effective Antimicrobials against Multidrug-Resistant Acinetobacter baumannii

2016 ◽  
Vol 60 (5) ◽  
pp. 2671-2679 ◽  
Author(s):  
Mya Thandar ◽  
Rolf Lood ◽  
Benjamin Y. Winer ◽  
Douglas R. Deutsch ◽  
Chad W. Euler ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Bacterial Pathogen ◽  
Antibacterial Activities ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Gram Negative ◽  
Content Type ◽  
Human Red Blood Cells ◽  
Phage Lysin

ABSTRACTAcinetobacter baumanniiis a Gram-negative bacterial pathogen responsible for a range of nosocomial infections. The recent rise and spread of multidrug-resistantA. baumanniiclones has fueled a search for alternative therapies, including bacteriophage endolysins with potent antibacterial activities. A common feature of these lysins is the presence of a highly positively charged C-terminal domain with a likely role in promoting outer membrane penetration. In the present study, we show that the C-terminal amino acids 108 to 138 of phage lysin PlyF307, named P307, alone were sufficient to killA. baumannii(>3 logs). Furthermore, P307 could be engineered for improved activity, the most active derivative being P307SQ-8C(>5-log kill). Both P307 and P307SQ-8Cshowed highin vitroactivity againstA. baumanniiin biofilms. Moreover, P307SQ-8Cexhibited MICs comparable to those of levofloxacin and ceftazidime and acted synergistically with polymyxin B. Although the peptides were shown to kill by disrupting the bacterial cytoplasmic membrane, they did not lyse human red blood cells or B cells; however, serum was found to be inhibitory to lytic activity. In a murine model ofA. baumanniiskin infection, P307SQ-8Creduced the bacterial burden by ∼2 logs in 2 h. This study demonstrates the prospect of using peptide derivatives from bacteriophage lysins to treat topical infections and remove biofilms caused by Gram-negative pathogens.

scholarly journals Disrupting Gram-Negative Bacterial Outer Membrane Biosynthesis through Inhibition of the Lipopolysaccharide Transporter MsbA

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Mary Kate Alexander ◽  
Anh Miu ◽  
Angela Oh ◽  
Mike Reichelt ◽  
Hoangdung Ho ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Drug Targets ◽  
Multidrug Resistant ◽  
Gram Negative Bacteria ◽  
Transport Pathway ◽  
Gram Negative ◽  
Content Type ◽  
Outer Leaflet ◽  
New Antibiotics ◽  
Outer Membrane Biogenesis

ABSTRACTThere is a critical need for new antibacterial strategies to counter the growing problem of antibiotic resistance. In Gram-negative bacteria, the outer membrane (OM) provides a protective barrier against antibiotics and other environmental insults. The outer leaflet of the outer membrane is primarily composed of lipopolysaccharide (LPS). Outer membrane biogenesis presents many potentially compelling drug targets as this pathway is absent in higher eukaryotes. Most proteins involved in LPS biosynthesis and transport are essential; however, few compounds have been identified that inhibit these proteins. The inner membrane ABC transporter MsbA carries out the first essential step in the trafficking of LPS to the outer membrane. We conducted a biochemical screen for inhibitors of MsbA and identified a series of quinoline compounds that killEscherichia colithrough inhibition of its ATPase and transport activity, with no loss of activity against clinical multidrug-resistant strains. Identification of these selective inhibitors indicates that MsbA is a viable target for new antibiotics, and the compounds we identified serve as useful tools to further probe the LPS transport pathway in Gram-negative bacteria.

scholarly journals Potentiation of Antibiotic Activity by a Novel Cationic Peptide: Potency and Spectrum of Activity of SPR741

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
David Corbett ◽  
Andrew Wise ◽  
Tara Langley ◽  
Kirsty Skinner ◽  
Emily Trimby ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Fusidic Acid ◽  
Bacterial Infections ◽  
Efflux Pump ◽  
Multidrug Resistant ◽  
Permeability Barrier ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Conventional Antibiotics

ABSTRACTNovel approaches for the treatment of multidrug-resistant Gram-negative bacterial infections are urgently required. One approach is to potentiate the efficacy of existing antibiotics whose spectrum of activity is limited by the permeability barrier presented by the Gram-negative outer membrane. Cationic peptides derived from polymyxin B have been used to permeabilize the outer membrane, granting antibiotics that would otherwise be excluded access to their targets. We assessed thein vitroefficacies of combinations of SPR741 with conventional antibiotics againstEscherichia coli,Klebsiella pneumoniae, andAcinetobacter baumannii. Of 35 antibiotics tested, the MICs of 8 of them were reduced 32- to 8,000-fold againstE. coliandK. pneumoniaein the presence of SPR741. The eight antibiotics, azithromycin, clarithromycin, erythromycin, fusidic acid, mupirocin, retapamulin, rifampin, and telithromycin, had diverse targets and mechanisms of action. AgainstA. baumannii, similar potentiation was achieved with clarithromycin, erythromycin, fusidic acid, retapamulin, and rifampin. Susceptibility testing of the most effective antibiotic-SPR741 combinations was extended to 25 additional multidrug-resistant or clinical isolates ofE. coliandK. pneumoniaeand 17 additionalA. baumanniiisolates in order to rank the potentiated antibiotics. SPR741 was also able to potentiate antibiotics that are substrates of the AcrAB-TolC efflux pump inE. coli, effectively circumventing the contribution of this pump to intrinsic antibiotic resistance. These studies support the further development of SPR741 in combination with conventional antibiotics for the treatment of Gram-negative bacterial infections.

scholarly journals A Proof-of-Concept Study of the Efficacy of Systemically Administered Polymyxins in Mouse Burn Wound Infection Caused by Multidrug-Resistant Gram-Negative Pathogens

2018 ◽  
Vol 62 (5) ◽  
Author(s):  
Yu-Wei Lin ◽  
Ke Chen ◽  
Jiping Wang ◽  
Tony Velkov ◽  
Qi Tony Zhou ◽  
...  
Keyword(s):  
Bacterial Load ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Infection Model ◽  
Wound Infections ◽  
Proof Of Concept ◽  
Burn Wound ◽  
Gram Negative ◽  
Content Type ◽  
Therapeutic Benefits

ABSTRACTThe efficacy of subcutaneously administered polymyxins against burn wound infections caused byPseudomonas aeruginosa,Acinetobacter baumannii, andKlebsiella pneumoniaewas examined in a murine infection model. Subcutaneously administered colistin and polymyxin B (30 mg/kg thrice daily) achieved a ≥2-log10reduction in the bacterial load forP. aeruginosaandA. baumanniiinfections, whereas wound infections byK. pneumoniaewere less responsive (<1-log10reduction). This study highlights the potential therapeutic benefits of parenteral polymyxins for treating burn wound infections.

scholarly journals Engineered Endolysin-Based “Artilysins” To Combat Multidrug-Resistant Gram-Negative Pathogens

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Yves Briers ◽  
Maarten Walmagh ◽  
Victor Van Puyenbroeck ◽  
Anneleen Cornelissen ◽  
William Cenens ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Wall ◽  
Outer Membrane ◽  
Multidrug Resistant ◽  
Resistant Bacteria ◽  
Gram Negative ◽  
Content Type ◽  
Bacterial Viruses ◽  
Cell Wall Hydrolysis

ABSTRACTThe global threat to public health posed by emerging multidrug-resistant bacteria in the past few years necessitates the development of novel approaches to combat bacterial infections. Endolysins encoded by bacterial viruses (or phages) represent one promising avenue of investigation. These enzyme-based antibacterials efficiently kill Gram-positive bacteria upon contact by specific cell wall hydrolysis. However, a major hurdle in their exploitation as antibacterials against Gram-negative pathogens is the impermeable lipopolysaccharide layer surrounding their cell wall. Therefore, we developed and optimized an approach to engineer these enzymes as outer membrane-penetrating endolysins (Artilysins), rendering them highly bactericidal against Gram-negative pathogens, includingPseudomonas aeruginosaandAcinetobacter baumannii. Artilysins combining a polycationic nonapeptide and a modular endolysin are able to kill these (multidrug-resistant) strainsin vitrowith a 4 to 5 log reduction within 30 min. We show that the activity of Artilysins can be further enhanced by the presence of a linker of increasing length between the peptide and endolysin or by a combination of both polycationic and hydrophobic/amphipathic peptides. Time-lapse microscopy confirmed the mode of action of polycationic Artilysins, showing that they pass the outer membrane to degrade the peptidoglycan with subsequent cell lysis. Artilysins are effectivein vitro(human keratinocytes) andin vivo(Caenorhabditis elegans).IMPORTANCEBacterial resistance to most commonly used antibiotics is a major challenge of the 21st century. Infections that cannot be treated by first-line antibiotics lead to increasing morbidity and mortality, while millions of dollars are spent each year by health care systems in trying to control antibiotic-resistant bacteria and to prevent cross-transmission of resistance. Endolysins—enzymes derived from bacterial viruses—represent a completely novel, promising class of antibacterials based on cell wall hydrolysis. Specifically, they are active against Gram-positive species, which lack a protective outer membrane and which have a low probability of resistance development. We modified endolysins by protein engineering to create Artilysins that are able to pass the outer membrane and become active againstPseudomonas aeruginosaandAcinetobacter baumannii, two of the most hazardous drug-resistant Gram-negative pathogens.

scholarly journals Lysocins: Bioengineered Antimicrobials That Deliver Lysins across the Outer Membrane of Gram-Negative Bacteria

2019 ◽  
Vol 63 (6) ◽  
Author(s):  
Ryan D. Heselpoth ◽  
Chad W. Euler ◽  
Raymond Schuch ◽  
Vincent A. Fischetti
Keyword(s):  
Outer Membrane ◽  
Receptor Binding ◽  
Standard Of Care ◽  
Multidrug Resistant ◽  
Gram Negative ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Surface Receptor ◽  
Inability To Work ◽  
Protein Channels

ABSTRACTThe prevalence of multidrug-resistantPseudomonas aeruginosahas stimulated development of alternative therapeutics. Bacteriophage peptidoglycan hydrolases, termed lysins, represent an emerging antimicrobial option for targeting Gram-positive bacteria. However, lysins against Gram-negatives are generally deterred by the outer membrane and their inability to work in serum. One solution involves exploiting evolved delivery systems used by colicin-like bacteriocins (e.g., S-type pyocins ofP. aeruginosa) to translocate through the outer membrane. Following surface receptor binding, colicin-like bacteriocins form Tol- or TonB-dependent translocons to actively import bactericidal domains through outer membrane protein channels. With this understanding, we developed lysocins, which are bioengineeredlysin-bacteriocinfusion molecules capable of periplasmic import. In our proof-of-concept studies, components from theP. aeruginosabacteriocin pyocin S2 (PyS2) responsible for surface receptor binding and outer membrane translocation were fused to the GN4 lysin to generate the PyS2-GN4 lysocin. PyS2-GN4 delivered the GN4 lysin to the periplasm to induce peptidoglycan cleavage and log-fold killing ofP. aeruginosawith minimal endotoxin release. While displaying narrow-spectrum antipseudomonal activity in human serum, PyS2-GN4 also efficiently disrupted biofilms, outperformed standard-of-care antibiotics, exhibited no cytotoxicity toward eukaryotic cells, and protected mice fromP. aeruginosachallenge in a bacteremia model. In addition to targetingP. aeruginosa, lysocins can be constructed to target other prominent Gram-negative bacterial pathogens.

scholarly journals Battacin (Octapeptin B5), a New Cyclic Lipopeptide Antibiotic from Paenibacillus tianmuensis Active against Multidrug-Resistant Gram-Negative Bacteria

2011 ◽  
Vol 56 (3) ◽  
pp. 1458-1465 ◽  
Author(s):  
Chao-Dong Qian ◽  
Xue-Chang Wu ◽  
Yi Teng ◽  
Wen-Peng Zhao ◽  
Ou Li ◽  
...  
Keyword(s):  
Polymyxin B ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Resistant Bacteria ◽  
Gram Negative Bacteria ◽  
Drug Resistant ◽  
Antibiotic Resistant ◽  
Gram Negative ◽  
Content Type ◽  
Lipopeptide Antibiotic

ABSTRACTHospital-acquired infections caused by drug-resistant bacteria are a significant challenge to patient safety. Numerous clinical isolates resistant to almost all commercially available antibiotics have emerged. Thus, novel antimicrobial agents, specifically those for multidrug-resistant Gram-negative bacteria, are urgently needed. In the current study, we report the isolation, structure elucidation, and preliminary biological characterization of a new cationic lipopeptide antibiotic, battacin or octapeptin B5, produced from aPaenibacillus tianmuensissoil isolate. Battacin kills bacteriain vitroand has potent activity against Gram-negative bacteria, including multidrug-resistant and extremely drug-resistant clinical isolates. Hospital strains ofEscherichia coliandPseudomonas aeruginosaare the pathogens most sensitive to battacin, with MICs of 2 to 4 μg/ml. The ability of battacin to disrupt the outer membrane of Gram-negative bacteria is comparable to that of polymyxin B, the last-line therapy for infections caused by antibiotic-resistant Gram-negative bacteria. However, the capacity of battacin to permeate bacterial plasma membranes is less extensive than that of polymyxin B. The bactericidal kinetics of battacin correlate with the depolarization of the cell membrane, suggesting that battacin kills bacteria by disrupting the cytoplasmic membrane. Other studies indicate that battacin is less acutely toxic than polymyxin B and has potentin vivobiological activity againstE. coli. Based on the findings of the current study, battacin may be considered a potential therapeutic agent for the treatment of infections caused by antibiotic-resistant Gram-negative bacteria.

scholarly journals The Anthelmintic Drug Niclosamide Synergizes with Colistin and Reverses Colistin Resistance in Gram-Negative Bacilli

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Ronald Domalaon ◽  
P. Malaka De Silva ◽  
Ayush Kumar ◽  
George G. Zhanel ◽  
Frank Schweizer
Keyword(s):  
Bacterial Infections ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Colistin Resistance ◽  
Bacterial Killing ◽  
Gram Negative ◽  
Content Type ◽  
Anthelmintic Drug ◽  
Lipopeptide Antibiotic ◽  
Approved Drugs

ABSTRACTThere is an urgent need for new therapies to overcome antimicrobial resistance especially in Gram-negative bacilli (GNB). Repurposing old U.S. Food and Drug Administration-approved drugs as complementary agents to existing antibiotics in a synergistic combination presents an attractive strategy. Here, we demonstrate that the anthelmintic drug niclosamide selectively synergized with the lipopeptide antibiotic colistin against colistin-susceptible but more importantly against colistin-resistant GNB, including clinical isolates that harbor themcr-1gene. Breakpoints for colistin susceptibility in resistant Gram-negative bacilli were reached in the presence of 1 μg/ml (3 μM) niclosamide. Reversal of colistin resistance was also observed in combinations of niclosamide and polymyxin B. Enhanced bacterial killing was evident for the combination, in comparison to colistin monotherapy, against resistantPseudomonas aeruginosa,Acinetobacter baumannii,Klebsiella pneumoniae,Escherichia coli, andEnterobacter cloacae. Accumulating evidence in the literature, along with our results, strongly suggests the potential for the combination of niclosamide and colistin to treat colistin-resistant Gram-negative bacillary infections. Our finding is significant since colistin is an antibiotic of last resort for multidrug-resistant Gram-negative bacterial infections that are nonresponsive to conventional treatments. With the recent global dissemination of plasmid-encoded colistin resistance, the addition of niclosamide to colistin therapy may hold the key to overcome colistin resistance.

scholarly journals Clinically Relevant Gram-Negative Resistance Mechanisms Have No Effect on the Efficacy of MC-1, a Novel Siderophore-Conjugated Monocarbam

2012 ◽  
Vol 56 (12) ◽  
pp. 6334-6342 ◽  
Author(s):  
Craig J. McPherson ◽  
Lisa M. Aschenbrenner ◽  
Brian M. Lacey ◽  
Kelly C. Fahnoe ◽  
Margaret M. Lemmon ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Outer Membrane ◽  
Negative Resistance ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Gram Negative ◽  
Content Type ◽  
Pharmacologically Active

ABSTRACTThe incidence of hospital-acquired infections with multidrug-resistant (MDR) Gram-negative pathogens is increasing at an alarming rate. Equally alarming is the overall lack of efficacious therapeutic options for clinicians, which is due primarily to the acquisition and development of various antibiotic resistance mechanisms that render these drugs ineffective. Among these mechanisms is the reduced permeability of the outer membrane, which prevents many marketed antibiotics from traversing this barrier. To circumvent this, recent drug discovery efforts have focused on conjugating a siderophore moiety to a pharmacologically active compound that has been designed to hijack the bacterial siderophore transport system and trick cells into importing the active drug by recognizing it as a nutritionally beneficial compound. MC-1, a novel siderophore-conjugated β-lactam that promotes its own uptake into bacteria, has exquisite activity against many Gram-negative pathogens. While the inclusion of the siderophore was originally designed to facilitate outer membrane penetration into Gram-negative cells, here we show that this structural moiety also renders other clinically relevant antibiotic resistance mechanisms unable to affect MC-1 efficacy. Resistance frequency determinations and subsequent characterization of first-step resistant mutants identified PiuA, a TonB-dependent outer membrane siderophore receptor, as the primary means of MC-1 entry intoPseudomonas aeruginosa. While the MICs of these mutants were increased 32-fold relative to the parental strainin vitro, we show that this resistance phenotype is not relevantin vivo, as alternative siderophore-mediated uptake mechanisms compensated for the loss of PiuA under iron-limiting conditions.

scholarly journals Prevalence of multidrug-resistant and extended-spectrum beta-lactamase producing Gram-negative isolates from clinical samples in a tertiary care hospital of Nepal

2021 ◽  
Vol 49 (1) ◽  
Author(s):  
Aryatara Shilpakar ◽  
Mehraj Ansari ◽  
Kul Raj Rai ◽  
Ganesh Rai ◽  
Shiba Kumar Rai
Keyword(s):  
Tertiary Care Hospital ◽  
Tertiary Care ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Confirmatory Test ◽  
Clinical Samples ◽  
Care Hospital ◽  
Gram Negative ◽  
Extended Spectrum ◽  
Esbl Producers

Abstract Background The existence of multidrug-resistant organisms, including extended-spectrum beta-lactamases (ESBLs), is on rise across the globe and is becoming a severe problem. Knowledge of the prevalence and antibiogram profile of such isolates is essential to develop an appropriate treatment methodology. This study aimed to study the prevalence of Gram-negative isolates exhibiting ESBL at a tertiary care hospital and study their antibiogram profile. Methods A cross-sectional study was conducted at Shahid Gangalal National Heart Centre, Kathmandu, Nepal, from June 2018 to November 2018. A total of 770 clinical samples were collected and identified using the conventional biochemical tests following the Clinical and Laboratory Standard Institute (CLSI) guidelines. Antimicrobial susceptibility testing (AST) was performed using the standardized Kirby-Bauer disk diffusion method. The screening test for ESBL producers was performed as recommended by the CLSI and the confirmatory test was performed phenotypically using the E-test. Results Out of the 92 isolates, 84 (91.3%) were multidrug-resistant, and 47 (51.1%) were found to be potential ESBL producers. Of these, 16 isolates were confirmed ESBL producers by the E-test. Escherichia coli and Klebsiella pneumoniae were the predominant isolates and were also the major ESBL producers. Besides polymyxin B (100% sensitive), meropenem and imipenem showed high efficacy against the ESBL producers. Conclusion Multidrug resistance was very high; however, ESBL production was low. Polymyxin B and carbapenems are the choice of drugs against ESBL producers but should be used only as the last line drugs.

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