scholarly journals The purine biosynthesis regulator PurR moonlights as a virulence regulator in Staphylococcus aureus

2019 ◽  
Vol 116 (27) ◽  
pp. 13563-13572 ◽  
Author(s):  
William E. Sause ◽  
Divya Balasubramanian ◽  
Irnov Irnov ◽  
Richard Copin ◽  
Mitchell J. Sullivan ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Ex Vivo ◽  
Purine Biosynthesis ◽  
In Vivo Studies ◽  
Human Neutrophils ◽  
Infection Models ◽  
Genes Encoding ◽  
Virulence Regulator

The pathogen Staphylococcus aureus colonizes and infects a variety of different sites within the human body. To adapt to these different environments, S. aureus relies on a complex and finely tuned regulatory network. While some of these networks have been well-elucidated, the functions of more than 50% of the transcriptional regulators in S. aureus remain unexplored. Here, we assess the contribution of the LacI family of metabolic regulators to staphylococcal virulence. We found that inactivating the purine biosynthesis regulator purR resulted in a strain that was acutely virulent in bloodstream infection models in mice and in ex vivo models using primary human neutrophils. Remarkably, these enhanced pathogenic traits are independent of purine biosynthesis, as the purR mutant was still highly virulent in the presence of mutations that disrupt PurR’s canonical role. Through the use of transcriptomics coupled with proteomics, we revealed that a number of virulence factors are differentially regulated in the absence of purR. Indeed, we demonstrate that PurR directly binds to the promoters of genes encoding virulence factors and to master regulators of virulence. These results guided us into further ex vivo and in vivo studies, where we discovered that S. aureus toxins drive the death of human phagocytes and mice, whereas the surface adhesin FnbA contributes to the increased bacterial burden observed in the purR mutant. Thus, S. aureus repurposes a metabolic regulator to directly control the expression of virulence factors, and by doing so, tempers its pathogenesis.

scholarly journals Serine-Aspartate Repeat Protein D Increases Staphylococcus aureus Virulence and Survival in Blood

2016 ◽  
Vol 85 (1) ◽  
Author(s):  
Fatemeh Askarian ◽  
Satoshi Uchiyama ◽  
J. Andrés Valderrama ◽  
Clement Ajayi ◽  
Johanna U. E. Sollid ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Ex Vivo ◽  
Innate Immune ◽  
Human Neutrophils ◽  
Infection Model ◽  
Bacterial Survival ◽  
Bacterial Killing ◽  
Content Type ◽  
Repeat Protein

ABSTRACT Staphylococcus aureus expresses a panel of cell wall-anchored adhesins, including proteins belonging to the microbial surface components recognizing adhesive matrix molecule (MSCRAMM) family, exemplified by the serine-aspartate repeat protein D (SdrD), which serve key roles in colonization and infection. Deletion of sdrD from S. aureus subsp. aureus strain NCTC8325-4 attenuated bacterial survival in human whole blood ex vivo, which was associated with increased killing by human neutrophils. Remarkably, SdrD was able to inhibit innate immune-mediated bacterial killing independently of other S. aureus proteins, since addition of recombinant SdrD protein and heterologous expression of SdrD in Lactococcus lactis promoted bacterial survival in human blood. SdrD contributes to bacterial virulence in vivo, since fewer S. aureus subsp. aureus NCTC8325-4 ΔsdrD bacteria than bacteria of the parent strain were recovered from blood and several organs using a murine intravenous infection model. Collectively, our findings reveal a new property of SdrD as an important key contributor to S. aureus survival and the ability to escape the innate immune system in blood.

scholarly journals Impact of Bicarbonate on PBP2a Production, Maturation, and Functionality in Methicillin-Resistant Staphylococcus aureus (MRSA)

2021 ◽  
Author(s):  
Selvi C. Ersoy ◽  
Henry F. Chambers ◽  
Richard A. Proctor ◽  
Adriana E. Rosato ◽  
Nagendra N. Mishra ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Ex Vivo ◽  
Carotenoid Content ◽  
Methicillin Resistant ◽  
Genes Encoding ◽  
Regulatory Impact ◽  
Mrsa Strains ◽  
The Impact

Certain methicillin-resistant Staphylococcus aureus (MRSA) strains exhibit β-lactam-susceptibility in vitro, ex vivo and in vivo in the presence of NaHCO3 (NaHCO3-responsive MRSA). Herein, we investigate the impact of NaHCO3 on factors required for PBP2a functionality. Prototype NaHCO3-responsive and -nonresponsive MRSA strains (as defined in vitro) were assessed for the impact of NaHCO3 on: expression of genes involved in PBP2a production-maturation pathways (mecA, blaZ, pbp4, vraSR, prsA, sigB, and floA); membrane PBP2a and PrsA protein content; and membrane carotenoid content. Following NaHCO3 exposure in NaHCO3-responsive (vs - nonresponsive) MRSA, there was significantly reduced expression of: i) mecA and blaZ; ii) the vraSR-prsA gene axis; and iii) pbp4. Carotenoid production was reduced, while floA expression was increased by NaHCO3 exposure in all MRSA strains. This work underscores the distinct regulatory impact of NaHCO3 on a cadre of genes encoding factors required for maintenance of the MRSA phenotype through PBP2a functionality and maturation.

scholarly journals Antivirulence Strategies for the Treatment of Staphylococcus aureus Infections: A Mini Review

2021 ◽  
Vol 11 ◽  
Author(s):  
Caleb A. Ford ◽  
Ian M. Hurford ◽  
James E. Cassat
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Tissue Injury ◽  
Therapeutic Targets ◽  
Multiple Infection ◽  
Human Pathogens ◽  
Host Immune Responses ◽  
Infection Models ◽  
Antimicrobial Treatments

Staphylococcus aureus is a Gram-positive bacterium capable of infecting nearly all host tissues, causing severe morbidity and mortality. Widespread antimicrobial resistance has emerged among S. aureus clinical isolates, which are now the most frequent causes of nosocomial infection among drug-resistant pathogens. S. aureus produces an array of virulence factors that enhance in vivo fitness by liberating nutrients from the host or evading host immune responses. Staphylococcal virulence factors have been identified as viable therapeutic targets for treatment, as they contribute to disease pathogenesis, tissue injury, and treatment failure. Antivirulence strategies, or treatments targeting virulence without direct toxicity to the inciting pathogen, show promise as an adjunctive therapy to traditional antimicrobials. This Mini Review examines recent research on S. aureus antivirulence strategies, with an emphasis on translational studies. While many different virulence factors have been investigated as therapeutic targets, this review focuses on strategies targeting three virulence categories: pore-forming toxins, immune evasion mechanisms, and the S. aureus quorum sensing system. These major areas of S. aureus antivirulence research demonstrate broad principles that may apply to other human pathogens. Finally, challenges of antivirulence research are outlined including the potential for resistance, the need to investigate multiple infection models, and the importance of studying antivirulence in conjunction with traditional antimicrobial treatments.

Identification of biologic agents to neutralize the bicomponent leukocidins of Staphylococcus aureus

2019 ◽  
Vol 11 (475) ◽  
pp. eaat0882 ◽  
Author(s):  
Rita Chan ◽  
Peter T. Buckley ◽  
Aidan O’Malley ◽  
William E. Sause ◽  
Francis Alonzo ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Immune Cells ◽  
Ex Vivo ◽  
Fibronectin Type Iii ◽  
Human Immune Response ◽  
Human Immune ◽  
Critical Components ◽  
Systemic Infections

A key aspect underlying the severity of infections caused by Staphylococcus aureus is the abundance of virulence factors that the pathogen uses to thwart critical components of the human immune response. One such mechanism involves the destruction of host immune cells by cytolytic toxins secreted by S. aureus, including five bicomponent leukocidins: PVL, HlgAB, HlgCB, LukED, and LukAB. Purified leukocidins can lyse immune cells ex vivo, and systemic injections of purified LukED or HlgAB can acutely kill mice. Here, we describe the generation and characterization of centyrins that bind S. aureus leukocidins with high affinity and protect primary human immune cells from toxin-mediated cytolysis. Centyrins are small protein scaffolds derived from the fibronectin type III–binding domain of the human protein tenascin-C. Although centyrins are potent in tissue culture assays, their short serum half-lives limit their efficacies in vivo. By extending the serum half-lives of centyrins through their fusion to an albumin-binding consensus domain, we demonstrate the in vivo efficacy of these biologics in a murine intoxication model and in models of both prophylactic and therapeutic treatment of live S. aureus systemic infections. These biologics that target S. aureus virulence factors have potential for treating and preventing serious staphylococcal infections.

Ex Vivo Inhibition of Platelet Aggregation in Patients with Severe Limb Arteriopathy Treated with BAY U3405, a Specific IX A2 Receptor Antagonist

1994 ◽  
Vol 72 (05) ◽  
pp. 659-662 ◽  
Author(s):  
S Bellucci ◽  
W Kedra ◽  
H Groussin ◽  
N Jaillet ◽  
P Molho-Sabatier ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Randomized Study ◽  
In Vivo Studies ◽  
Walking Distance ◽  
Peripheral Blood Flow ◽  
Walking Ability ◽  
Double Blind ◽  
Platelet Factor

SummaryA double-blind, placebo-controlled randomized study with BAY U3405, a specific thromboxane A2 (TX A2) receptor blocker, was performed in patients suffering from severe stade II limb arteriopathy. BAY U3405 or placebo was administered in 16 patients at 20 mg four times a day (from day 1 to day 3). Hemostatic studies were done before therapy, and on day 2 and day 3 under therapy. On day 3, BAY U3405 was shown to induce a highly statistically significant decrease of the velocity and the intensity of the aggregations mediated by arachidonic acid (56 ± 37% for the velocity, 58 ± 26% for the intensity) or by U46619 endoperoxide analogue (36 ± 35% for the velocity, 37 ± 27% for the intensity). Similar results were already observed on day 2. By contrast, such a decrease was not noticed with ADP mediated platelet aggregation. Furthermore, plasma levels of betathrombo-globulin and platelet factor 4 remained unchanged. Peripheral hemodynamic parameters were also studied. The peripheral blood flow was measured using a Doppler ultrasound; the pain free walking distance and the total walking ability distance were determined under standardized conditions on a treadmill. These last two parameters show a trend to improvement which nevertheless was not statistically significant. All together these results encourage further in vivo studies using BAY U3405 or related compounds on a long-term administration.

Chemical Permeation Enhancers for Transdermal Delivery of Thiocolchicoside: Assessment of Ex-vivo Skin Flux and In-vivo Pharmacokinetics

2017 ◽  
Vol 10 (5) ◽  
pp. 3827-3835
Author(s):  
Y Madhusudan Rao ◽  
Gayatri P ◽  
Ajitha M ◽  
P. Pavan Kumar ◽  
Kiran kumar
Keyword(s):  
Passive Control ◽  
Ex Vivo ◽  
Skin Permeation ◽  
In Vivo Studies ◽  
Permeation Enhancers ◽  
Casting Technique ◽  
Chemical Permeation Enhancers ◽  
Chemical Permeation ◽  
In Vivo Pharmacokinetics

Present investigation comprises the study of ex-vivo skin flux and in-vivo pharmacokinetics of Thiocolchicoside (THC) from transdermal films. The films were fabricated by solvent casting technique employing combination of hydrophilic and hydrophobic polymers. A flux of 18.08 µg/cm2h and 13.37µg/cm2h was achieved for optimized formulations containing 1, 8-cineole and oleic acid respectively as permeation enhancers. The observed flux values were higher when compared to passive control (8.66 µg/cm2h). Highest skin permeation was observed when 1,8-cineole was used as chemical permeation enhancer and it considerably (2-2.5 fold) improved the THC transport across the rat skin. In vivo studies were performed in rabbits and samples were analysed by LC-MS-MS. The mean area under the curve (AUC) values of transdermal film showed about 2.35 times statistically significant (p<0.05) improvement in bioavailability when compared with the oral administration of THC solution. The developed transdermal therapeutic systems using chemical permeation enhancers were suitable for drugs like THC in effective management of muscular pain.    

Monocytes as Carriers of Magnetic Nanoparticles for Tracking Inflammation in the Epileptic Rat Brain

2019 ◽  
Vol 16 (7) ◽  
pp. 637-644 ◽  
Author(s):  
Hadas Han ◽  
Sara Eyal ◽  
Emma Portnoy ◽  
Aniv Mann ◽  
Miriam Shmuel ◽  
...  
Keyword(s):  
Brain Tissue ◽  
Ex Vivo ◽  
In Vivo Studies ◽  
Nanoparticle Distribution ◽  
Spontaneous Seizures ◽  
Systemic Distribution ◽  
Hippocampal Ca1 ◽  
Pilocarpine Model

Background: Inflammation is a hallmark of epileptogenic brain tissue. Previously, we have shown that inflammation in epilepsy can be delineated using systemically-injected fluorescent and magnetite- laden nanoparticles. Suggested mechanisms included distribution of free nanoparticles across a compromised blood-brain barrier or their transfer by monocytes that infiltrate the epileptic brain. Objective: In the current study, we evaluated monocytes as vehicles that deliver nanoparticles into the epileptic brain. We also assessed the effect of epilepsy on the systemic distribution of nanoparticleloaded monocytes. Methods: The in vitro uptake of 300-nm nanoparticles labeled with magnetite and BODIPY (for optical imaging) was evaluated using rat monocytes and fluorescence detection. For in vivo studies we used the rat lithium-pilocarpine model of temporal lobe epilepsy. In vivo nanoparticle distribution was evaluated using immunohistochemistry. Results: 89% of nanoparticle loading into rat monocytes was accomplished within 8 hours, enabling overnight nanoparticle loading ex vivo. The dose-normalized distribution of nanoparticle-loaded monocytes into the hippocampal CA1 and dentate gyrus of rats with spontaneous seizures was 176-fold and 380-fold higher compared to the free nanoparticles (p<0.05). Seizures were associated with greater nanoparticle accumulation within the liver and the spleen (p<0.05). Conclusion: Nanoparticle-loaded monocytes are attracted to epileptogenic brain tissue and may be used for labeling or targeting it, while significantly reducing the systemic dose of potentially toxic compounds. The effect of seizures on monocyte biodistribution should be further explored to better understand the systemic effects of epilepsy.

Phenolic Acids Exert Anticholinesterase and Cognition-Improving Effects

2018 ◽  
Vol 15 (6) ◽  
pp. 531-543 ◽  
Author(s):  
Dominik Szwajgier ◽  
Ewa Baranowska-Wojcik ◽  
Kamila Borowiec
Keyword(s):  
Phenolic Acids ◽  
Ex Vivo ◽  
Amyloid Β ◽  
Inhibitory Effect ◽  
In Vivo Studies ◽  
Amyloid Β Peptide ◽  
Beneficial Effects ◽  
Aβ Fibrils

Numerous authors have provided evidence regarding the beneficial effects of phenolic acids and their derivatives against Alzheimer's disease (AD). In this review, the role of phenolic acids as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is discussed, including the structure-activity relationship. In addition, the inhibitory effect of phenolic acids on the formation of amyloid β-peptide (Aβ) fibrils is presented. We also cover the in vitro, ex vivo, and in vivo studies concerning the prevention and treatment of the cognitive enhancement.

Development, Pre-clinical Investigation and Histopathological Evaluation of Metronidazole Loaded Topical Formulation for Treatment of Skin Inflammatory disorders

2020 ◽  
Vol 10 ◽  
Author(s):  
Divya Thakur ◽  
Gurpreet Kaur ◽  
Sheetu Wadhwa ◽  
Ashana Puri
Keyword(s):  
Ex Vivo ◽  
Clinical Investigation ◽  
In Vivo Studies ◽  
Tween 20 ◽  
Inflammatory Disorders ◽  
Rat Paw Edema ◽  
Ex Vivo Permeation ◽  
Permeation Studies ◽  
Anti Inflammatory

Background: Metronidazole (MTZ) is an anti-oxidant and anti-inflammatory agent with beneficial therapeutic properties. The hydrophilic nature of molecule limits its penetration across the skin. Existing commercial formulations have limitations of inadequate drug concentration present at target site, which requires frequent administration and poor patient compliance. Objective: The aim of current study was to develop and evaluate water in oil microemulsion of Metronidazole with higher skin retention for treatment of inflammatory skin disorders. Methods: Pseudo ternary phase diagrams were used in order to select the appropriate ratio of surfactant and co-surfactant and identify the microemulsion area. The selected formulation consisted of Capmul MCM as oil, Tween 20 and Span 20 as surfactant and co-surfactant, respectively, and water. The formulation was characterized and evaluated for stability, Ex vivo permeation studies and in vivo anti-inflammatory effect (carrageenan induced rat paw edema, air pouch model), anti-psoriatic activity (mouse-tail test). Results: The particle size analyses revealed average diameter and polydispersity index of selected formulation to be 16 nm and 0.373, respectively. The results of ex vivo permeation studies showed statistically higher mean cumulative amount of MTZ retained in rat skin from microemulsion i.e. 21.90 ± 1.92 μg/cm2 which was 6.65 times higher as compared to Marketed gel (Metrogyl gel®) with 3.29 ± 0.11 μg/cm2 (p<0.05). The results of in vivo studies suggested the microemulsion based formulation of MTZ to be similar in efficacy to Metrogyl gel®. Conclusion: Research suggests efficacy of the developed MTZ loaded microemulsion in treatment of chronic skin inflammatory disorders.

scholarly journals Evaluation of a bone filler scaffold for local antibiotic delivery to prevent Staphylococcus aureus infection in a contaminated bone defect

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Karen E. Beenken ◽  
Mara J. Campbell ◽  
Aura M. Ramirez ◽  
Karrar Alghazali ◽  
Christopher M. Walker ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Bone Defect ◽  
Rabbit Model ◽  
In Vivo Studies ◽  
Bovine Bone ◽  
Bone Filler ◽  
Antibiotic Release ◽  
Local Antibiotic ◽  
Antibiotic Delivery

AbstractWe previously reported the development of an osteogenic bone filler scaffold consisting of degradable polyurethane, hydroxyapatite, and decellularized bovine bone particles. The current study was aimed at evaluating the use of this scaffold as a means of local antibiotic delivery to prevent infection in a bone defect contaminated with Staphylococcus aureus. We evaluated two scaffold formulations with the same component ratios but differing overall porosity and surface area. Studies with vancomycin, daptomycin, and gentamicin confirmed that antibiotic uptake was concentration dependent and that increased porosity correlated with increased uptake and prolonged antibiotic release. We also demonstrate that vancomycin can be passively loaded into either formulation in sufficient concentration to prevent infection in a rabbit model of a contaminated segmental bone defect. Moreover, even in those few cases in which complete eradication was not achieved, the number of viable bacteria in the bone was significantly reduced by treatment and there was no radiographic evidence of osteomyelitis. Radiographs and microcomputed tomography (µCT) analysis from the in vivo studies also suggested that the addition of vancomycin did not have any significant effect on the scaffold itself. These results demonstrate the potential utility of our bone regeneration scaffold for local antibiotic delivery to prevent infection in contaminated bone defects.

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