scholarly journals Evaluation of Sb-1 bacteriophage activity in enhancing antibiotic efficacy against biofilm, degrading the exopolysaccharide matrix and targeting persister cells of Staphylococcus aureus

2018 ◽  
Author(s):  
Tamta Tkhilaishvili ◽  
Lisa Lombardi ◽  
Ann-Brit Klatt ◽  
Andrej Trampuz ◽  
Mariagrazia Di Luca
Keyword(s):  
Staphylococcus Aureus ◽  
Fluorescent Microscopy ◽  
Persister Cells ◽  
Planktonic Bacteria ◽  
The Matrix ◽  
Lower Titer ◽  
Pre Treatment ◽  
Direct Killing ◽  
Antibiotic Efficacy ◽  
Specific Bacteriophage

AbstractMost research on phage therapy focused on planktonic bacteria, whereas bacteriophage activity against biofilms is limited. We evaluated the capability of Staphylococcus aureus-specific bacteriophage Sb-1 to eradicate biofilm alone and in combination with different classes of antibiotics, to degrade the extracellular matrix and target persister cells. Biofilm of methicillin-resistant S. aureus (MRSA) ATCC 43300 was treated with Sb-1 alone or in (simultaneous or staggered) combination with either fosfomycin, rifampin, vancomycin, daptomycin or ciprofloxacin. The matrix was visualized by confocal fluorescent microscopy. Persister cells were treated with 104 and 107 PFU/mL Sb-1 for 3 hours in PBS, followed by CFU counting. Alternatively, bacteria were washed and incubated in fresh BHI medium and the bacterial growth assessed after further 24-hours. Pre-treatment with Sb-1 followed by the administration of sub-inhibitory concentrations of antibiotic exerted a considerable synergistic effect in eradicating MRSA biofilm. Sb-1 determined a dose-dependent reduction of matrix exopolysaccharide. 107 PFU/mL Sb-1 showed direct killing activity on persisters. However, even a lower titer had lytic activity when phage-treated persister cells were inoculated in fresh medium, reverting to a normal-growing phenotype. This study provides valuable data regarding the capability of Sb-1 to enhance antibiotic efficacy, exhibiting specific antibiofilm features. Its ability to degrade the MRSA polysaccharide matrix and target persister cells makes Sb-1 suitable for the therapy of biofilm-associated infections.

scholarly journals Recalcitrant Staphylococcus aureus infections: obstacles and solutions

2021 ◽  
Author(s):  
Sarah E. Rowe ◽  
Jenna E. Beam ◽  
Brian P. Conlon
Keyword(s):  
Staphylococcus Aureus ◽  
Physiological State ◽  
Cell Types ◽  
Persister Cells ◽  
Single Solution ◽  
New Antibiotics ◽  
Direct Targeting ◽  
Conventional Antibiotics ◽  
Antibiotic Efficacy

Antibiotic treatment failure of Staphylococcus aureus infections is very common. In addition to genetically encoded mechanisms of antibiotic resistance, numerous additional factors limit the efficacy of antibiotics in vivo. Identifying and removing the barriers to antibiotic efficacy is of major importance as even if new antibiotics become available, they will likely face the same barriers to efficacy as their predecessors. One major obstacle to antibiotic efficacy is the proficiency of S. aureus to enter a physiological state that is incompatible with antibiotic killing. Multiple pathways leading to antibiotic tolerance and the formation of tolerant sub-populations called persister cells, have been described for S. aureus. Additionally, S. aureus is a versatile pathogen that can infect numerous tissues and invade a variety of cell types, some of which are poorly penetrable to antibiotics. It is therefore unlikely that there will be a single solution to the problem of recalcitrant S. aureus infection. Instead, specific approaches may be required to target tolerant cells within different niches, be it through direct targeting of persister cells, sensitization of persisters to conventional antibiotics, improved penetration of antibiotics to particular niches or any combination thereof. Here we examine two well described reservoirs of antibiotic tolerant S. aureus, the biofilm and the macrophage, the barriers these environments present to antibiotic efficacy and potential solutions to the problem.

scholarly journals Manipulation of Autophagy in Phagocytes Facilitates Staphylococcus aureus Bloodstream Infection

2015 ◽  
Vol 83 (9) ◽  
pp. 3445-3457 ◽  
Author(s):  
Kate M. O'Keeffe ◽  
Mieszko M. Wilk ◽  
John M. Leech ◽  
Alison G. Murphy ◽  
Maisem Laabei ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Systemic Infection ◽  
Critical Factor ◽  
Intracellular Survival ◽  
Autophagic Flux ◽  
Content Type ◽  
Bactericidal Effects ◽  
Staphylococcus Aureus Bloodstream Infection ◽  
Direct Killing

The capacity for intracellular survival within phagocytes is likely a critical factor facilitating the dissemination ofStaphylococcus aureusin the host. To date, the majority of work onS. aureus-phagocyte interactions has focused on neutrophils and, to a lesser extent, macrophages, yet we understand little about the role played by dendritic cells (DCs) in the direct killing of this bacterium. Using bone marrow-derived DCs (BMDCs), we demonstrate for the first time that DCs can effectively killS. aureusbut that certain strains ofS. aureushave the capacity to evade DC (and macrophage) killing by manipulation of autophagic pathways. Strains with high levels of Agr activity were capable of causing autophagosome accumulation, were not killed by BMDCs, and subsequently escaped from the phagocyte, exerting significant cytotoxic effects. Conversely, strains that exhibited low levels of Agr activity failed to accumulate autophagosomes and were killed by BMDCs. Inhibition of the autophagic pathway by treatment with 3-methyladenine restored the bactericidal effects of BMDCs. Using anin vivomodel of systemic infection, we demonstrated that the ability ofS. aureusstrains to evade phagocytic cell killing and to survive temporarily within phagocytes correlated with persistence in the periphery and that this effect is critically Agr dependent. Taken together, our data suggest that strains ofS. aureusexhibiting high levels of Agr activity are capable of blocking autophagic flux, leading to the accumulation of autophagosomes. Within these autophagosomes, the bacteria are protected from phagocytic killing, thus providing an intracellular survival niche within professional phagocytes, which ultimately facilitates dissemination.

Abstract 51: Thymosin β4 Targets Wisp1 to Protect Cardiomyocytes in AngII- induced Cardiac Hypertrophy

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Sudhiranjan Gupta ◽  
Li Li ◽  
Rakesh Guleria ◽  
Kenneth M Baker
Keyword(s):  
Cardiac Hypertrophy ◽  
Fluorescent Microscopy ◽  
Marker Genes ◽  
Protective Mechanism ◽  
Ang Ii ◽  
Hypertrophic Response ◽  
Antiapoptotic Proteins ◽  
Neonatal Cardiomyocytes ◽  
Cell Proliferation And Differentiation ◽  
Pre Treatment

Background: Thymosin beta-4 (Tβ4) is a ubiquitous protein with many properties relating to cell proliferation and differentiation that promotes wound healing and modulates inflammatory mediators. However, the role of Tβ4 in cardiomyocytes hypertrophy is currently unknown. The purpose of this study is to dissect the cardio-protective mechanism of Tβ4 in Ang II induced cardiac hypertrophy. Methods: Rat neonatal cardiomyocytes with or without Tβ4 pretreatment were stimulated with Ang II and expression of cell sizes, hypertrophy marker genes and Wnt signaling components was evaluated by quantitative real-time PCR, western blotting and fluorescent microscopy. Selected target gene Wisp-1 was either overexpressed or silenced by siRNA transfections in neonatal cardiomyocytes and effect of Tβ4 in Ang II-induced cardiac hypertrophy was evaluated. Results: Pre-treatment of Tβ4 resulted in reduction of cell sizes, hypertrophy marker genes and WNT-associated gene expression and levels induced by Ang II in cardiomyocytes. Tβ4 pretreatment also resulted in an increase in the expression of antiapoptotic proteins and reduction of Bax/BCl 2 ratio in the cardiomyocytes. Wisp-1 overexpression promotes cardiac hypertrophy and was reversed by pretreatment with Tβ4. Knocking down of Wisp1 partly rescue the cells from hypertrophic response after Tβ4 treatment. Conclusion: This is the first report that demonstrates the effect of Tβ4 on cardiomyocytes hypertrophy and its capability to selectively target Wisp-1 in neonatal cardiomyocytes thus preventing cell death, thereby, protecting the myocardium. Wisp-1 promotes the cardiac hypertrophy which was prevented by Tβ4 treatment.

Effect of Laser Pre-Treatment on the Machining Performance of Aluminum/SiC MMC

2003 ◽  
Vol 125 (4) ◽  
pp. 378-384 ◽  
Author(s):  
Stuart Barnes ◽  
Richard Morgan ◽  
Andrew Skeen
Keyword(s):  
Tool Wear ◽  
Wear Mechanism ◽  
Laser Heating ◽  
Surface Damage ◽  
Edge Condition ◽  
Machining Performance ◽  
Matrix Properties ◽  
The Matrix ◽  
Pre Treatment ◽  
Measuring Tool

Although the abrasive reinforcement in MMCs primarily controls their machining behavior, the properties of the matrix also exert an influence. A 1200 W diode laser was used, due to the large footprint (5×0.3 mm) and the short wavelength (0.94 μm) to pre-treat a 2618 (18% SiC) alloy. The laser heating and self-quenching of the material modified the matrix properties. Machining performance was then assessed by measuring tool wear and edge condition, cutting forces, surface finish, and sub-surface damage. Results indicated that pre-treatment gave less wear, lower forces, and less sub-surface damage although abrasion remained the primary wear mechanism.

Determination of 22 trace elements in high-purity copper including Se and Te by ETV-ICP OES using SF6, NF3, CF4and H2as chemical modifiers

2016 ◽  
Vol 31 (3) ◽  
pp. 642-657 ◽  
Author(s):  
J. Hassler ◽  
R. Matschat ◽  
S. Richter ◽  
P. Barth ◽  
A. K. Detcheva ◽  
...  
Keyword(s):  
Trace Elements ◽  
High Purity ◽  
Icp Oes ◽  
Chemical Modifiers ◽  
The Matrix ◽  
Scope Of Application ◽  
Pre Treatment ◽  
Purity Copper

Experiments with SF6, NF3, CF4and H2as new modifier gases for the matrix studied were performed. Pre-treatment steps of sub-samples (e.g., roasting) can now be omitted; the scope of application was enlarged to Au and hydride forming elements (such as Se, Te).

scholarly journals Antibiotic Susceptibility Study Of Metal-Gentamicin Complexes Against Staphylococcus Aureus Biofilms

2017 ◽  
Vol 16 (2) ◽  
Author(s):  
Intan Azura Shahdan ◽  
Fatimah Zahrah Mohd Sobri ◽  
Mohammad Faiz Hizzuan Hanapi ◽  
Hanani Ahmad Yusof ◽  
Fiona N.-F. How
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Susceptibility ◽  
Bacterial Species ◽  
Dental Biofilm ◽  
Planktonic Bacteria ◽  
Metal Contents ◽  
Susceptibility Study ◽  
Biofilm Bacteria ◽  
Dental Plaques ◽  
Conventional Antibiotics

Introduction: Dental plaque is a structurally and functionally organized biofilm. Modern molecular biological techniques have identified about 1000 different bacterial species in the dental biofilm, twice as many as can be cultured. Inherent resistance of biofilm bacteria to conventional antibiotics is alarming. It induces antibiotic resistance to an order of three or more in magnitude greater than those displayed by planktonic bacteria. Staphylococcus aureus is the most dominant bacterial species isolated from the saliva and dental plaques. One of the reasons for its pathogenicity is its ability to form biofilms. In this study, the resistance of S. aureus biofilms against a eries of metal-antibiotics, an alternative to the conventional antibiotics, was investigated. Materials and Methods: A series of metal-antibiotic complexes derived from gentamicin was synthesized to give metal-gentamicin complexes. The metal contents of all the compounds were determined using Atomic Absorption Spectroscopy (AAS). Antibiotic susceptibility testing of the gentamicin-antibiotic complexes against several strains of S. aureus biofilms was conducted using broth microdilution assay. Results: The results showed that S. aureus is susceptible against Co(II) and Fe(II) gentamicin complexes; all were tested at 0.25 to 1 mmol concentrations. Conclusion(s): Co(II) and Fe(II)-gentamicin complexes demonstrated antimicrobial activity.

scholarly journals Biofilm/Persister/Stationary Phase Bacteria Cause More Severe Disease Than Log Phase Bacteria – II Infection with Persister Forms of Staphylococcus aureus Causes a Chronic Persistent Skin Infection with More Severe Lesion that Takes Longer to Heal and is not Eradicated by the Current Recommended Treatment in Mice

2018 ◽  
Author(s):  
Rebecca Yee ◽  
Yuting Yuan ◽  
Cory Brayton ◽  
Andreina Tarff Leal ◽  
Jie Feng ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Stationary Phase ◽  
Skin Infection ◽  
Bacterial Load ◽  
Mouse Skin ◽  
Infection Model ◽  
Persister Cells ◽  
Persistent Infections ◽  
Recommended Treatment ◽  
Biofilm Bacteria

AbstractStaphylococcus aureus is an opportunistic pathogen that can cause persistent infections clinically. Treatment for chronic S. aureus infections ranges from at least one week to several months and such infections are prone to relapse likely due to the presence of persistent forms of bacteria such as persister cells. Persister cells, which are bacterial cells that become dormant under stress conditions, can be isolated in vitro but their clinical significance in in vivo infections are largely unclear. Here, we evaluated S. aureus persistent forms using stationary phase cultures and biofilm bacteria (enriched in persisters) in comparison with log phase cultures in terms of their ability to cause disease in a mouse skin infection model. Surprisingly, we found that infection of mice with stationary phase cultures and biofilm bacteria produced a more severe chronic skin infection with more pronounced lesions which took longer to heal than log phase (actively growing) cultures. After two week infection, the bacterial load and skin tissue pathology, as determined by hyperplasia, immune cell infiltration, and crust/lesion formation, of mice infected with the more persistent forms (e.g. stationary phase bacteria and biofilm bacteria) were greater than mice infected with log phase bacteria. Using our persistent infection mouse model, we showed that the clinically recommended treatment for recurrent S. aureus skin infection, doxycycline + rifampin, was not effective in eradicating the bacteria in the treatment study, despite reducing lesion sizes and pathology in infected mice. Analogous findings were also observed in a Caenorhabditis elegans model, where S.aureus stationary phase cultures caused a greater mortality than log phase culture as early as two days post-infection. Thus, we established a new model for chronic persistent infections using persister bacteria that could serve as a relevant model to evaluate therapeutic options for persistent infections in general. Our findings connect persisters with persistent infections, have implications for understanding disease pathogenesis, and are likely to be broadly valid for other pathogens.

Degradation of recalcitrant organic contaminants by solar photocatalysis

2007 ◽  
Vol 55 (12) ◽  
pp. 119-125 ◽  
Author(s):  
L. Mansouri ◽  
L. Bousselmi ◽  
A. Ghrabi
Keyword(s):  
Organic Contaminants ◽  
Order Kinetic ◽  
Biological Degradation ◽  
Solar Photocatalysis ◽  
Photocatalytic Reactor ◽  
Operational Conditions ◽  
Toc Removal ◽  
The Matrix ◽  
Pre Treatment ◽  
Refractory Organic Pollutants

Biological pre-treated landfill leachates of Djebel Chakir contains some macromolecular organic substances that are resistant to biological degradation. The aim of the present work is to assess the feasibility of removing refractory organic pollutants in biological pre-treated landfill leachate by solar photocatalyse process. Leachate pollutant contents are studied to assess their contribution to leachate pollution and their treatability by solar photocatalyse process. Phenol is chosen as model of pollutants, to evaluate its removal and the efficiency of the photocatalytic system. The experiments were carried out in suspended photocatalytic reactor, using TiO2 Degussa P25, under sunlight illumination (UV-A: 15–31 W/cm2). Under optimum operational conditions, applied to single reactant (phenol), the system presents a TOC removal of 90% (the degradation follows a first-order kinetic). Based on the TOC removal, the results shows that the degradation of biological pre-treated leachate follows a zero-order kinetic. After 5 h of sunlight exposure, 74% of COT is removed. The TOC removal is the best without any correction of the pH and at the TiO2 concentration of 2.5 g/L. The photocatalytic degradation of organic contaminants as well as the formation and disappearance of the by-products were followed by GC/MS. The solar photocatalysis processes induce several modifications of the matrix leading to more biodegradable forms: all the remaining and new compounds generated after the biological pre-treatment of leachate are degraded and other types of organics appear, mainly carboxylic acid, aliphatic hydrocarbons and phtalic acids.

scholarly journals Properties of Latex Polymer Modified Mortars Reinforced with Waste Bamboo Fibers from Construction Waste

Buildings ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 149 ◽  
Author(s):  
Banjo Akinyemi ◽  
Temidayo Omoniyi
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Latex Paint ◽  
Construction Waste ◽  
Calcium Silicate Hydrates ◽  
Cement Mortars ◽  
The Matrix ◽  
Bamboo Fibers ◽  
Pre Treatment ◽  
Scanning Electron

This study evaluated the properties of latex modified cement mortars from ordinary paints which were reinforced with treated bamboo fibers from construction waste. Fiber variations of 0, 0.5, 1 and 1.5% at 10% of the weight of cement were utilized. Mechanical properties were determined according to standards; similarly, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the microstructural and elemental properties of the samples. The experimental results revealed that the addition of 1.5% bamboo fibers and 10% latex solution produced excellent mechanical properties. This was as a result of improved fiber adhesion to the matrix through pre-treatment, coupled with the contributed high strength from the latex paint modified mortars. The micrograph showed that latex precipitated in the voids and on the surface of the bamboo fibers as well as gels of calcium silicate hydrates which contributed to the observed improvement in strength of the tested samples.

scholarly journals A selective membrane-targeting repurposed antibiotic with activity against persistent methicillin-resistant Staphylococcus aureus

2019 ◽  
Vol 116 (33) ◽  
pp. 16529-16534 ◽  
Author(s):  
Wooseong Kim ◽  
Guijin Zou ◽  
Taylor P. A. Hari ◽  
Ingrid K. Wilt ◽  
Wenpeng Zhu ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Membrane Fluidity ◽  
Lipid Bilayers ◽  
Therapeutic Agent ◽  
Md Simulations ◽  
Persister Cells ◽  
Methicillin Resistant ◽  
Bacterial Membranes ◽  
Selective Membrane ◽  
Mrsa Infection

Treatment of Staphylococcus aureus infections is complicated by the development of antibiotic tolerance, a consequence of the ability of S. aureus to enter into a nongrowing, dormant state in which the organisms are referred to as persisters. We report that the clinically approved anthelmintic agent bithionol kills methicillin-resistant S. aureus (MRSA) persister cells, which correlates with its ability to disrupt the integrity of Gram-positive bacterial membranes. Critically, bithionol exhibits significant selectivity for bacterial compared with mammalian cell membranes. All-atom molecular dynamics (MD) simulations demonstrate that the selectivity of bithionol for bacterial membranes correlates with its ability to penetrate and embed in bacterial-mimic lipid bilayers, but not in cholesterol-rich mammalian-mimic lipid bilayers. In addition to causing rapid membrane permeabilization, the insertion of bithionol increases membrane fluidity. By using bithionol and nTZDpa (another membrane-active antimicrobial agent), as well as analogs of these compounds, we show that the activity of membrane-active compounds against MRSA persisters positively correlates with their ability to increase membrane fluidity, thereby establishing an accurate biophysical indicator for estimating antipersister potency. Finally, we demonstrate that, in combination with gentamicin, bithionol effectively reduces bacterial burdens in a mouse model of chronic deep-seated MRSA infection. This work highlights the potential repurposing of bithionol as an antipersister therapeutic agent.

Sign in / Sign up

Export Citation Format

Share Document