scholarly journals Mechanism of Enhanced Activity of Liposome-Entrapped Aminoglycosides against Resistant Strains of Pseudomonas aeruginosa

2006 ◽  
Vol 50 (6) ◽  
pp. 2016-2022 ◽  
Author(s):  
Clement Mugabe ◽  
Majed Halwani ◽  
Ali O. Azghani ◽  
Robert M. Lafrenie ◽  
Abdelwahab Omri
Keyword(s):  
Flow Cytometry ◽  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Fusion Rate ◽  
Bacterial Cells ◽  
Antibiotic Resistant ◽  
Transmission Electron ◽  
Resistant Strains ◽  
Conventional Antibiotics ◽  
Liposomal Drugs

ABSTRACT Pseudomonas aeruginosa is inherently resistant to most conventional antibiotics. The mechanism of resistance of this bacterium is mainly associated with the low permeability of its outer membrane to these agents. We sought to assess the bactericidal efficacy of liposome-entrapped aminoglycosides against resistant clinical strains of P. aeruginosa and to define the mechanism of liposome-bacterium interactions. Aminoglycosides were incorporated into liposomes, and the bactericidal efficacies of both free and liposomal drugs were evaluated. To define the mechanism of liposome-bacterium interactions, transmission electron microscopy (TEM), flow cytometry, lipid mixing assay, and immunocytochemistry were employed. Encapsulation of aminoglycosides into liposomes significantly increased their antibacterial activity against the resistant strains used in this study (MICs of ≥32 versus ≤8 μg/ml). TEM observations showed that liposomes interact intimately with the outer membrane of P. aeruginosa, leading to the membrane deformation. The flow cytometry and lipid mixing assays confirmed liposome-bacterial membrane fusion, which increased as a function of incubation time. The maximum fusion rate was 54.3% ± 1.5% for an antibiotic-sensitive strain of P. aeruginosa and 57.8% ± 1.9% for a drug-resistant strain. The fusion between liposomes and P. aeruginosa significantly enhanced the antibiotics' penetration into the bacterial cells (3.2 ± 2.3 versus 24.2 ± 6.2 gold particles/bacterium, P ≤ 0.001). Our data suggest that liposome-entrapped antibiotics could successfully resolve infections caused by antibiotic-resistant P. aeruginosa through an enhanced mechanism of drug entry into the bacterial cells.

Mechanisms involved in effects of antimicrobial peptides, bactenectins ChBac3.4, ChBac5, and mini-ChBac7.5Nb, on bacterial cells

2017 ◽  
pp. 43-50
Author(s):  
О.В. Шамова ◽  
М.С. Жаркова ◽  
П.М. Копейкин ◽  
Д.С. Орлов ◽  
Е.А. Корнева
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Innate Immunity ◽  
Infectious Diseases ◽  
Metabolic Activity ◽  
Capra Hircus ◽  
Bacterial Cells ◽  
Antibiotic Resistant ◽  
Resistant Strains

Антимикробные пептиды (АМП) системы врожденного иммунитета - соединения, играющие важную роль в патогенезе инфекционных заболеваний, так как обладают свойством инактивировать широкий спектр патогенных бактерий, обеспечивая противомикробную защиту живых организмов. В настоящее время АМП рассматриваются как потенциальные соединения-корректоры инфекционной патологии, вызываемой антибиотикорезистентными бактериями (АБР). Цель данной работы состояла в изученим механизмов антибактериального действия трех пептидов, принадлежащих к семейству бактенецинов - ChBac3.4, ChBac5 и mini-ChBac7.5Nb. Эти химически синтезированные пептиды являются аналогами природных пролин-богатых АМП, обнаруженных в лейкоцитах домашней козы Capra hircus и проявляющих высокую антимикробную активность, в том числе и в отношении грамотрицательных АБР. Методы. Минимальные ингибирующие и минимальные бактерицидные концентрации пептидов (МИК и МБК) определяли методом серийных разведений в жидкой питательной среде с последующим высевом на плотную питательную среду. Эффекты пептидов на проницаемость цитоплазматической мембраны бактерий для хромогенного маркера исследовали с использованием генетически модифицированного штамма Escherichia coli ML35p. Действие бактенецинов на метаболическую активность бактерий изучали с применением маркера резазурина. Результаты. Показано, что все исследованные пептиды проявляют высокую антимикробную активность в отношении Escherichia coli ML35p и антибиотикоустойчивых штаммов Escherichia coli ESBL и Acinetobacter baumannii in vitro, но их действие на бактериальные клетки разное. Использован комплекс методик, позволяющих наблюдать в режиме реального времени динамику действия бактенецинов в различных концентрациях (включая их МИК и МБК) на барьерную функцию цитоплазматической мембраны и на интенсивность метаболизма бактериальных клеток, что дало возможность выявить различия в характере воздействия бактенецинов, отличающихся по структуре молекулы, на исследуемые микроорганизмы. Установлено, что действие каждого из трех исследованных бактенецинов в бактерицидных концентрациях отличается по эффективности нарушения целостности бактериальных мембран и в скорости подавления метаболизма клеток. Заключение. Полученная информация дополнит существующие фундаментальные представления о механизмах действия пролин-богатых пептидов врожденного иммунитета, а также послужит основой для биотехнологических исследований, направленных на разработку на базе этих соединений новых антибиотических препаратов для коррекции инфекционных заболеваний, вызываемых АБР и являющимися причинами тяжелых внутрибольничных инфекций. Antimicrobial peptides (AMPs) of the innate immunity are compounds that play an important role in pathogenesis of infectious diseases due to their ability to inactivate a broad array of pathogenic bacteria, thereby providing anti-microbial host defense. AMPs are currently considered promising compounds for treatment of infectious diseases caused by antibiotic-resistant bacteria. The aim of this study was to investigate molecular mechanisms of the antibacterial action of three peptides from the bactenecin family, ChBac3.4, ChBac5, and mini-ChBac7.5Nb. These chemically synthesized peptides are analogues of natural proline-rich AMPs previously discovered by the authors of the present study in leukocytes of the domestic goat, Capra hircus. These peptides exhibit a high antimicrobial activity, in particular, against antibiotic-resistant gram-negative bacteria. Methods. Minimum inhibitory and minimum bactericidal concentrations of the peptides (MIC and MBC) were determined using the broth microdilution assay followed by subculturing on agar plates. Effects of the AMPs on bacterial cytoplasmic membrane permeability for a chromogenic marker were explored using a genetically modified strain, Escherichia coli ML35p. The effect of bactenecins on bacterial metabolic activity was studied using a resazurin marker. Results. All the studied peptides showed a high in vitro antimicrobial activity against Escherichia coli ML35p and antibiotic-resistant strains, Escherichia coli ESBL and Acinetobacter baumannii, but differed in features of their action on bacterial cells. The used combination of techniques allowed the real-time monitoring of effects of bactenecin at different concentrations (including their MIC and MBC) on the cell membrane barrier function and metabolic activity of bacteria. The differences in effects of these three structurally different bactenecins on the studied microorganisms implied that these peptides at bactericidal concentrations differed in their capability for disintegrating bacterial cell membranes and rate of inhibiting bacterial metabolism. Conclusion. The obtained information will supplement the existing basic concepts on mechanisms involved in effects of proline-rich peptides of the innate immunity. This information will also stimulate biotechnological research aimed at development of new antibiotics for treatment of infectious diseases, such as severe in-hospital infections, caused by antibiotic-resistant strains.

scholarly journals Vaccination with Outer Membrane Complexes Elicits Rapid Protective Immunity to Multidrug-ResistantAcinetobacter baumannii

2010 ◽  
Vol 79 (1) ◽  
pp. 518-526 ◽  
Author(s):  
Michael J. McConnell ◽  
Juan Domínguez-Herrera ◽  
Younes Smani ◽  
Rafael López-Rojas ◽  
Fernando Docobo-Pérez ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protective Immunity ◽  
Cellular Responses ◽  
Antibiotic Resistant ◽  
Membrane Complex ◽  
Sepsis Model ◽  
Cytokine Levels ◽  
Prophylactic Vaccination ◽  
Resistant Strains ◽  
Established Infection

ABSTRACTAcinetobacter baumanniicauses pneumonias, bacteremias, and skin and soft tissue infections, primarily in the hospitalized setting. The incidence of infections caused byA. baumanniihas increased dramatically over the last 30 years, while at the same time the treatment of these infections has been complicated by the emergence of antibiotic-resistant strains. Despite these trends, no vaccines or antibody-based therapies have been developed for the prevention ofA. baumanniiinfection. In this study, an outer membrane complex vaccine consisting of multiple surface antigens from the bacterial membrane ofA. baumanniiwas developed and tested in a murine sepsis model. Immunization elicited humoral and cellular responses that were able to reduce postinfection bacterial loads, reduce postinfection proinflammatory cytokine levels in serum, and protect mice from infection with human clinical isolates ofA. baumannii. A single administration of the vaccine was able to elicit protective immunity in as few as 6 days postimmunization. In addition, vaccine antiserum was used successfully to therapeutically rescue naïve mice with established infection. These results indicate that prophylactic vaccination and antibody-based therapies based on an outer membrane complex vaccine may be viable approaches to preventing the morbidity and mortality caused by this pathogen.

scholarly journals Biological Properties of Structurally Related α-Helical Cationic Antimicrobial Peptides

1999 ◽  
Vol 67 (4) ◽  
pp. 2005-2009 ◽  
Author(s):  
Monisha G. Scott ◽  
Hong Yan ◽  
Robert E. W. Hancock
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Tumor Necrosis ◽  
Biological Properties ◽  
Cationic Antimicrobial Peptide ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Resistant Strains ◽  
Conventional Antibiotics ◽  
Necrosis Factor

ABSTRACT A series of α-helical cationic antimicrobial peptide variants with small amino acid changes was designed. Alterations in the charge, hydrophobicity, or length of the variant peptides did not improve the antimicrobial activity, and there was no statistically significant correlation between any of these factors and the MIC forPseudomonas aeruginosa, Escherichia coli, orSalmonella typhimurium. Individual peptides demonstrated synergy with conventional antibiotics against antibiotic-resistant strains of P. aeruginosa. The peptides varied considerably in the ability to bind E. coli O111:B4 lipopolysaccharide (LPS), and this correlated significantly with their antimicrobial activity and ability to block LPS-stimulated tumor necrosis factor and interleukin-6 production. In general, the peptides studied here demonstrated a broad range of activities, including antimicrobial, antiendotoxin, and enhancer activities.

scholarly journals Antibacterial Activity of Synthetic Cationic Iron Porphyrins

Antioxidants ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 972
Author(s):  
Artak Tovmasyan ◽  
Ines Batinic-Haberle ◽  
Ludmil Benov
Keyword(s):  
Bactericidal Activity ◽  
Protoporphyrin Ix ◽  
Laboratory Animals ◽  
Bacterial Cells ◽  
Decomposition Products ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Resistant Strains ◽  
Positively Charged ◽  
New Strategies

Widespread antibiotic resistance demands new strategies for fighting infections. Porphyrin-based compounds were long ago introduced as photosensitizers for photodynamic therapy, but light-independent antimicrobial activity of such compounds has not been systematically explored. The results of this study demonstrate that synthetic cationic amphiphilic iron N-alkylpyridylporphyrins exert strong bactericidal action at concentrations as low as 5 μM. Iron porphyrin, FeTnHex-2-PyP, which is well tolerated by laboratory animals, efficiently killed Gram-negative and Gram-positive microorganisms. Its bactericidal activity was oxygen-independent and was controlled by the lipophilicity and accumulation of the compound in bacterial cells. Such behavior is in contrast with the anionic gallium protoporphyrin IX, whose efficacy depends on cellular heme uptake systems. Under aerobic conditions, however, the activity of FeTnHex-2-PyP was limited by its destruction due to redox-cycling. Neither iron released from the Fe-porphyrin nor other decomposition products were the cause of the bactericidal activity. FeTnHex-2-PyP was as efficient against antibiotic-sensitive E. coli and S. aureus as against their antibiotic-resistant counterparts. Our data demonstrate that development of amphiphilic, positively charged metalloporphyrins might be a promising approach in the introduction of new weapons against antibiotic-resistant strains.

scholarly journals The Response of Pseudomonas aeruginosa PAO1 to UV-activated Titanium Dioxide/Silica Nanotubes

2020 ◽  
Vol 21 (20) ◽  
pp. 7748
Author(s):  
Adrian Augustyniak ◽  
Krzysztof Cendrowski ◽  
Bartłomiej Grygorcewicz ◽  
Joanna Jabłońska ◽  
Paweł Nawrotek ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Titanium Dioxide ◽  
Biofilm Formation ◽  
Efflux Pump ◽  
Uv Light ◽  
Alternative Methods ◽  
Silica Nanotubes ◽  
Antibiotic Resistant ◽  
Metabolic Functions ◽  
Resistant Strains

Pseudomonas aeruginosa is a bacterium of high clinical and biotechnological importance thanks to its high adaptability to environmental conditions. The increasing incidence of antibiotic-resistant strains has created a need for alternative methods to increase the chance of recovery in infected patients. Various nanomaterials have the potential to be used for this purpose. Therefore, we aimed to study the physiological response of P. aeruginosa PAO1 to titanium dioxide/silica nanotubes. The results suggest that UV light-irradiated nanomaterial triggers strong agglomeration in the studied bacteria that was confirmed by microscopy, spectrophotometry, and flow cytometry. The effect was diminished when the nanomaterial was applied without initial irradiation, with UV light indicating that the creation of reactive oxygen species could play a role in this phenomenon. The nanocomposite also affected biofilm formation ability. Even though the biomass of biofilms was comparable, the viability of cells in biofilms was upregulated in 48-hour biofilms. Furthermore, from six selected genes, the mexA coding efflux pump was upregulated, which could be associated with an interaction with TiO2. The results show that titanium dioxide/silica nanotubes may alter the physiological and metabolic functions of P. aeruginosa PAO1.

scholarly journals Metal ions and graphene-based compounds as alternative treatment options for burn wounds infected by antibiotic-resistant Pseudomonas aeruginosa

2020 ◽  
Vol 202 (5) ◽  
pp. 995-1004 ◽  
Author(s):  
Nathalie Karaky ◽  
Andrew Kirby ◽  
Andrew J. McBain ◽  
Jonathan A. Butler ◽  
Mohamed El Mohtadi ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Metal Ions ◽  
Treatment Options ◽  
Major Complication ◽  
Antimicrobial Effect ◽  
Bacterial Cells ◽  
Biofilm Inhibition ◽  
Antibiotic Resistant ◽  
Topical Antimicrobials

AbstractBurn infections caused by Pseudomonas aeruginosa pose a major complication in wound healing. This study aimed to determine the antimicrobial effect of metal ions, graphene (Gr), and graphene oxide (GO), individually and in combination, against the planktonic and biofilm states of two antimicrobially resistant clinical strains of P. aeruginosa each with different antibiotic resistance profiles. Minimum inhibitory, minimum bactericidal, and fractional inhibitory concentrations were performed to determine the efficacy of the metal ions and graphene composites individually and their synergy in combination. Crystal violet biofilm and XTT assays measured the biofilm inhibition and metabolic activity, respectively. Molybdenum, platinum, tin, gold, and palladium ions exhibited the greatest antimicrobial activity (MIC = 7.8–26.0 mg/L), whilst GO and Gr demonstrated moderate-to-no effect against the planktonic bacterial cells, irrespective of their antibiograms. Biofilms were inhibited by zinc, palladium, silver, and graphene. In combination, silver–graphene and molybdenum–graphene inhibited both the planktonic and biofilm forms of the bacteria making them potential candidates for development into topical antimicrobials for burns patients infected with antibiotic-resistant P. aeruginosa.

scholarly journals Alleviation of Pseudomonas aeruginosa Infection by Propeptide-Mediated Inhibition of Protease IV

2021 ◽  
Author(s):  
Tae-Hyeon Kim ◽  
Xi-Hui Li ◽  
Joon-Hee Lee
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistant ◽  
Content Type ◽  
Pseudomonas Aeruginosa Infection ◽  
Protease Iv ◽  
Conventional Antibiotics

Pseudomonas aeruginosa is a highly antibiotic-resistant pathogen and is extremely difficult to treat. Instead of using conventional antibiotics, we attempted to alleviate P. aeruginosa infection using factors that P. aeruginosa itself produces naturally.

Adaptive resistance to polymyxin in Pseudomonas aeruginosa due to an outer membrane impermeability mechanism

1982 ◽  
Vol 28 (7) ◽  
pp. 830-840 ◽  
Author(s):  
H. E. Gilleland Jr. ◽  
Linda B. Farley
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Resistant Strain ◽  
Cytoplasmic Membrane ◽  
Osmotic Shock ◽  
Membrane Repair ◽  
Permeability Characteristics ◽  
Minimal Inhibitory Concentrations ◽  
Adaptive Resistance ◽  
Resistant Strains

The isolated outer membrane from cells of a Pseudomonas aeruginosa strain exhibiting adaptive resistance to polymyxin was not affected by polymyxin treatment, as monitored by electron microscopy of negatively stained preparations. This was in sharp contrast with extensive disruption by polymyxin of the outer membranes of the parent polymyxin-sensitive strain and the resistant strain following reversion to greater polymyxin sensitivity. The isolated cytoplasmic membrane of the polymyxin-resistant strain, on the other hand, remained sensitive to the disruptive effects of polymyxin treatment. The permeability characteristics of the resistant strains appeared to be altered, as indicated by differences in minimal inhibitory concentrations for a variety of antibiotics between the polymyxin-sensitive and polymyxin-resistant strains. No evidence was found for a polymyxin-inactivating enzyme in osmotic shock fluid from the polymyxin-resistant strain. No evidence for a cytoplasmic membrane repair mechanism was found in the polymyxin-resistant strain. These observations suggest that the mechanism of adaptive polymyxin resistance in this model system is the alteration of the outer membrane so that it excludes polymyxin from reaching the still sensitive cytoplasmic membrane.

scholarly journals Sensitivity of antibiotic resistant coagulase-negative staphylococci to antiseptic piсloxydin in eye drops Vitabact

2020 ◽  
Author(s):  
Anait Khalatyan ◽  
Maria Budzinskaya ◽  
Ekaterina Kholina ◽  
Marina Strakhovskaya ◽  
Nadezhda Kolyshkina ◽  
...  
Keyword(s):  
High Efficiency ◽  
In Vitro Tests ◽  
Eye Drops ◽  
Bacterial Cells ◽  
Coagulase Negative Staphylococci ◽  
Destructive Effect ◽  
Antibiotic Resistant ◽  
Normal Microflora ◽  
Resistant Strains

Background. Coagulase-negative staphylococci (CNS), primarily Staphylococcus epidermidis, predominate in the normal microflora of the eye. However, due to irrational antibiotic therapy, resistant strains are widely distributed among CNS. Objective. To study the sensitivity of the antibiotic resistant CNS isolates to the antiseptic picloxydine dihydrochloride ("Vitabact"). Methods. Species, sensitivity to antibiotics and antiseptic picloxydine dihydrochloride were determined for 39 isolates of bacteria obtained from the conjunctival swabs. The cells morphology under the influence of antiseptic was studied by electron microscopy. Results. 33 isolates of S. epidermidis (17 sensitive or resistant to drugs of no more than 2 classes of antibiotics and 16 MDR), 2 S. haemolyticus (1 resistant to 2 classes of antibiotics and 1 MDR), 3 S. hominis (1 sensitive and 2 MDR), 1 S. caprae (MDR) were characterized. In vitro tests, the antiseptic picloxydine dihydrochloride showed high efficiency in suppressing the growth of staphylococci regardless of their sensitivity to antibiotics, as well as bactericidal activity at concentration of 31.2 g/ml. In this concentration, the antiseptic had a pronounced destructive effect on the surface structures of bacterial cells. Conclusion. Antiseptic picloxydine dihydrochloride is effective against antibiotic resistant coagulase-negative staphylococci.

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