Comparison of Antibacterial Activity and Wound Healing in a Superficial Abrasion Mouse Model of Staphylococcus aureus Skin Infection Using Photodynamic Therapy Based on Methylene Blue or Mupirocin or Both

Emerging strategies and therapeutic innovations for combating drug resistance in Staphylococcus aureus strains: A comprehensive review

In recent years, antibiotic therapy has encountered significant challenges due to the rapid emergence of multidrug resistance among bacteria responsible for life-threatening illnesses, creating uncertainty about the future management of infectious diseases. The escalation of antimicrobial resistance in the post-COVID era compared to the pre-COVID era has raised global concern. The prevalence of nosocomial-related infections, especially outbreaks of drug-resistant strains of Staphylococcus aureus, have been reported worldwide, with India being a notable hotspot for such occurrences. Various virulence factors and mutations characterize nosocomial infections involving S. aureus. The lack of proper alternative treatments leading to increased drug resistance emphasizes the need to investigate and examine recent research to combat future pandemics. In the current genomics era, the application of advanced technologies such as next-generation sequencing (NGS), machine learning (ML), and quantum computing (QC) for genomic analysis and resistance prediction has significantly increased the pace of diagnosing drug-resistant pathogens and insights into genetic intricacies. Despite prompt diagnosis, the elimination of drug-resistant infections remains unattainable in the absence of effective alternative therapies. Researchers are exploring various alternative therapeutic approaches, including phage therapy, antimicrobial peptides, photodynamic therapy, vaccines, host-directed therapies, and more. The proposed review mainly focuses on the resistance journey of S. aureus over the past decade, detailing its resistance mechanisms, prevalence in the subcontinent, innovations in rapid diagnosis of the drug-resistant strains, including the applicants of NGS and ML application along with QC, it helps to design alternative novel therapeutics approaches against S. aureus infection.

Anti-bacterial and anti-inflammatory properties of Vernonia arborea accelerate the healing of infected wounds in adult Zebrafish

BACKGROUND

Management of wounds and healing under impaired conditions are the major challenges faced globally by healthcare workers. Phytocompounds which are anti-microbial and capable of modulating inflammation contribute to overall wound healing and regain of the lost structure and function especially in wounds impaired with polymicrobial infection.

METHODS

An acute cutaneous impaired wound model using adult zebrafish was validated to simulate mammalian wound pathophysiology. This model was used to evaluate phytofractions of Vernonia arborea in the present study, for reduction of infection; myeloperoxidase (MPO) as a marker of infection; neutrophil infiltration and resolution; kinetics of inflammatory cytokines; and wound repair kinetics (viz., nitrite levels and iNoS expression; reepithelisation).

RESULTS

Four fractions which were active in-vitro against five selected wound microbes were shown to reduce ex-vivo microbial bioburden upto 96% in the infected wound tissue. The reduction in CFU correlated with the neutrophil kinetics and MPO enzyme levels in the treated, wound infected zebrafish. Expression of pro-inflammatory cytokines (IL-6 and TNF-α) was downregulated while upregulating anti-inflammatory cytokine (IL-10), and nitric oxide signalling with fourfold increase in iNOS expression. The adult zebrafish wound model could well serve as a standard tool for assessing phytoextracts such as V. arborea for wound healing with anti-microbial properties.

Evaluation of topical methylene blue nanoemulsion for wound healing in diabetic mice

CONTEXT

Diabetic wounds (DW) are a complication of diabetes and slow wound healing is the main manifestation. Methylene blue (MB) has been shown to exhibit therapeutic effects on diabetes-related diseases.

OBJECTIVE

To investigate the mechanisms of action of MB-nanoemulsion (NE) in the treatment of DW.

MATERIALS AND METHODS

The concentration of MB-NE used in the in vivo and in vitro experiments was 0.1 mg/mL. Streptozocin-induced diabetic mice were used as models. The mice were separated into nondiabetic, diabetic, MB-NE treated, and NE-treated groups. Intervention of high glucose-induced human umbilical vein endothelial cells using MB-NE. The mechanism by which MB-NE promotes DW healing is investigated by combining histological analysis, immunofluorescence analysis, TUNEL and ROS assays and western blotting.

RESULTS

In diabetic mice, the MB-NE accelerated DW healing (p < 0.05), promoted the expression of endothelial cell markers (α-SMA, CD31 and VEGF) (p < 0.05), and reduced TUNEL levels. In vitro, MB accelerated the migration rate of cells (p < 0.05); promoted the expression of CD31, VEGF, anti-apoptotic protein Bcl2 (p < 0.05) and decreased the expression of the pro-apoptotic proteins cleaved caspase-3 and Bax (p < 0.05). MB upregulated the expression of Nrf2, catalase, HO-1 and SOD2 (p < 0.05). In addition, MB reduced the immunofluorescence intensity of TUNEL and ROS in cells and reduced apoptosis. The therapeutic effect of MB was attenuated after treatment with an Nrf2 inhibitor (ML385).

DISCUSSION AND CONCLUSION

This study provides a foundation for the application of MB-NE in the treatment of DW.

Antibacterial nanocomposite of chitosan/silver nanocrystals/graphene oxide (ChAgG) development for its potential use in bioactive wound dressings

An adequate wound dressing reduces time of healing, provides cost-effective care, thereby improving patients' quality life. An antimicrobial bioactivity is always desired, for that reason, the objective of this work is to design an antimicrobial nanocomposite of chitosan/silver nanocrystals/graphene oxide (ChAgG). ChAgG nanostructured composite material is composed of chitosan from corn (Ch), and silver nanocrystals from garlic (Allium sativum). The nanocomposite obtained is the result of a series of experiments combining the graphene oxide (GrOx) with two members of the Amaryllidaceae family; garlic and onion (Allium cebae), which contain different sulfur materials. The characterization arrays confirmed the successful production of silver crystal, graphene oxidation and the blending of both components. The role of the chitosan as a binder between graphene and silver nanocrystals is proved. Moreover, the study discusses garlic as an optimal source that permits the synthesis of silver nanocrystals (AgNCs) (⁓ 2 to 10 nm) with better thermal and crystallinity properties. It was also confirmed the successful production of the ChAgG nanocomposite. Escherichia coli and Staphylococcus aureus were used to demonstrate the antibacterial bioactivity and L-929 fibroblast cells were utilized to visualize their biocompatibility. The proposed ChAgG nanomaterial will be useful for functionalizing specific fiber network that represents current challenging research in the fabrication of bioactive wound dressings.

Study on skin infection model of Staphylococcus aureus based on analytic hierarchy process and Delphi method

Purpose

Infectious skin diseases are a type of inflammatory skin lesions caused by pathogenic microorganisms. Because of the uncertainty of methodology, the skin infection model usually have low replication rate and lack of good evaluation system. We aimed to establish multi-index and comprehensive evaluation method for Staphylococcus aureus (S.aureus) skin-infection models through Analytic hierarchy process (AHP) and Delphi method, and screen high quality animal models through it.

Materials and methods

Firstly, the evaluation indicators of skin infection were collected basing on literature research. The weight of the evaluation indicators were decided according to AHP and Delphi method. Then different ulcer models (mouse or rat) infected by S. aureus were selected as the research objects.

Results

The evaluation indicators were classified into four groups of criteria (including ten sub-indicators) and given different weights, physical sign changes (0.0518), skin lesion appearance (0.2934), morphological observation (0.3184), etiological examination (0.3364). Through the evaluation system, we screened and found that the mouse ulcer model which caused by a round wound and 1.0 × 10¹⁰ CFU/mL (0.1 mL) bacterial concentration got the highest comprehensive score, and also found that the model which caused by a 1.5 cm-round wound and 1.0 × 10¹⁰ CFU/mL (0.2 mL) maybe the best rat ulcer model.

Conclusions

This study has established an evaluation system based on AHP and Delphi method, also provided the best skin ulcer models selected by this system, the models are suitable for disease research and drug development research of skin ulcer.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Infection-activated lipopeptide nanotherapeutics with adaptable geometrical morphology for in vivo bacterial ablation

The nonselective membrane disruption of antimicrobial peptides (AMPs) helps in combating the antibacterial resistance. But their overall positive charges lead to undesirable hemolysis and toxicity toward normal living cells, as well as the rapid clearance from blood circulation. In consequence, developing smart AMPs to optimize the antimicrobial outcomes is highly urgent. Relying on the local acidity of microbial infection sites, in this work, we designed an acidity-triggered charge reversal nanotherapeutics with adaptable geometrical morphology for bacterial targeting and optimized therapy. C₁₆-A₃K₄-CONH₂ was proposed and the ε-amino groups in lysine residues were acylated by dimethylmaleic amide (DMA), enabling the generated C₁₆-A₃K₄(DMA)-CONH₂ to self-assemble into negatively charged spherical nanostructure, which relieved the protein adsorption and prolonged blood circulation in vivo. After the access of C₁₆-A₃K₄(DMA)-CONH₂ into the microbial infection sites, acid-sensitive β-carboxylic amide would hydrolyze to regenerate the positive C₁₆-A₃K₄-CONH₂ to destabilize the negatively charged bacterial membrane. In the meanwhile, attractively, the self-assembled spherical nanoparticle transformed to rod-like nanostructure, which was in favor of the efficient binding with bacterial membranes due to the larger contact area. Our results showed that the acid-activated AMP nanotherapeutics exhibited strong and broad-spectrum antimicrobial activities against Yeast, Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli, and methicillin-resistant Staphylococcus aureus (MRSA). Moreover, the biocompatible lipopeptide nanotherapeutics dramatically improved the dermapostasis caused by bacterial infection. The strategy of merging pathology-activated therapeutic function and morphological adaptation to augment therapeutic outcomes shows the great potential for bacterial inhibition. STATEMENT OF SIGNIFICANCE: The overall positive charges of antimicrobial peptides (AMPs) lead to undesirable hemolysis and nonselective toxicity, as well as the rapid clearance from blood circulation. Infection-activated lipopeptide nanotherapeutics with adaptable geometrical morphology were developed to address these issues. The self-assembled lipopeptide was pre-decorated to reverse the positive charge to reduce the hemolysis and nonselective cytotoxicity. After accessing the acidic infection sites, the nanotherapeutics recovered the positive charge to destabilize negatively charged bacterial membranes. Meanwhile, the morphology of self-assembled nanotherapeutics transformed from spherical nanoparticles to rod-like nanostructures in the lesion site, facilitating the improved association with bacterial membranes to boost the therapeutic efficiency. These results provide new design rationale for AMPs developed for bacterial inhibition.

Bacteriocins Revitalize Non-Effective Penicillin G to Overcome Methicillin-Resistant Staphylococcus pseudintermedius

The rise of antibiotic-resistant bacteria is among the biggest challenges in human and veterinary medicine. One of the major factors that contributes to resistance is use of frontline clinical antibiotics in veterinary practices. To avoid this problem, searching for antimicrobials aimed at veterinary applications is becoming especially important. Thiopeptide micrococcin P1 and leaderless peptide EntEJ97s are two different bacteriocins that are very active against many gram-positive bacteria; however, sensitive bacteria can rapidly develop resistance towards those bacteriocins. To overcome this problem, we searched for synergy between those bacteriocins and conventional antibiotics against methicillin-resistant Staphylococcus pseudintermedius (MRSP): a common pathogen in animal skin infections. The two bacteriocins acted synergistically with each other and with penicillin G against MRSP clinical isolates in both planktonic and biofilm assays; they also prevented resistance development. The therapeutic potential was further validated in a murine skin infection model that showed that a combination of micrococcin P1, EntEJ97s and penicillin G reduced cell-forming units of MRSP by 2-log10 CFU/g. Taken together, our data show that a combination of bacteriocins with conventional antibiotics can not only prevent resistance development but also pave the way to revitalize some old, less useful antibiotics, such as penicillin, which by itself has no effect on methicillin-resistant pathogens.

The photosensitizer-based therapies enhance the repairing of skin wounds

Wound repair remains a clinical challenge and bacterial infection is a common complication that may significantly delay healing. Therefore, proper and effective wound management is essential. The photosensitizer-based therapies mainly stimulate the photosensitizer to generate reactive oxygen species through appropriate excitation source irradiation, thereby killing pathogenic microorganisms. Moreover, they initiate local immune responses by inducing the recruitment of immune cells as well as the production of proinflammatory cytokines. In addition, these therapies can stimulate the proliferation, migration and differentiation of skin resident cells, and improve the deposition of extracellular matrix; subsequently, they promote the re-epithelialization, angiogenesis, and tissue remodeling. Studies in multiple animal models and human skin wounds have proved that the superior sterilization property and biological effects of photosensitizer-based therapies during different stages of wound repair. In this review, we summarize the recent advances in photosensitizer-based therapies for enhancing tissue regeneration, and suggest more effective therapeutics for patients with skin wounds.

Topical Application of Premna integrifolia Linn on Skin Wound Injury in Rats Accelerates the Wound Healing Process: Evidence from In Vitro and In Vivo Experimental Models

Background

When the skin and tissues within the body are injured, the healing process begins. Medicinal herbs have been used to cure wounds since time immemorial. The antimicrobial and antioxidant activity possessed by P. integrifolia may accelerate wound healing.

Objectives

To assess the wound healing activity of Premna integrifolia extract (PIE) by employing in-vivo experimental animal models and an in-vitro migration scratch assay. Furthermore, to assess its cytotoxicity using the MTT assay.

Methods

Wistar albino rats were used for the in vivo wound healing models. The animals were divided into four groups at random: Group I was untreated. Group II was vehicle control (ointment base). Group III was PIE ointment (5% W/W). Group IV was standard (povidone-iodine ointment) (5% W/W). The ointments were applied directly to the wounds as described above until they healed completely. The wound contraction percentage and tensile strength were calculated. The MTT test was used to determine the viability of the test extract against the fibroblast cells. The scratch assay was used in vitro to determine the wound healing potential of the test drug. P ≤ 0.05 values were considered statistically significant.

Results

Premna integrifolia extract did not possess any noticeable cytotoxicity to the cell line and showed an IC50 of 185.98 μg/ml. The wound contraction potential of PIE ointment-treated animals was considerably greater (P ≤ 0.001) on days 4, 8, 12, 16, and 20 when compared to the control group. The percentage of wound contraction on day 20 was 99.92% in PIE-treated animals compared to 83.23% in untreated animals. Compared to the untreated group, the duration of full epithelization was significantly (P ≤ 0.01) shorter in the test group. When compared to the incision control group, the animals treated with PIE ointment had significantly higher (P ≤ 0.001) tensile strength. In addition, animals given the test drug had a significant (P ≤ 0.001) increase in total protein and hydroxyproline. In the in vitro scratch assay, test drug-treated cells demonstrated greater cell migration. Histology images confirmed that the test drug-treated group had epithelial tissue proliferation and keratinization.

Conclusion

The current study found that Premna integrifolia improved wound healing activity both in vitro and in vivo. These findings indicate that Premna integrifolia extract has wound-healing potential and could be a viable source of nutraceuticals with wound-healing properties.

Mupirocin Promotes Wound Healing by Stimulating Growth Factor Production and Proliferation of Human Keratinocytes

Mupirocin has been reported for its role in the treatment of infected wounds through its antibacterial activity, however the role of mupirocin in promoting wound healing via alternative mechanisms has not been extensively evaluated. This study aimed to evaluate the potential effect of mupirocin to promote wound healing, not only through its antibacterial activity but by increasing human keratinocyte proliferation and growth factor production. In the scratch assay, using human keratinocytes (HaCat), mupirocin (at 0.1 and 0.2 mM) significantly increased wound closure compared to the vehicle control. Cell viability, measured from the scratch assay, verified the increase in wound closure, where mupirocin at both concentrations showed higher cell viability compared to the vehicle control. In addition, mupirocin at 0.1 mM significantly stimulated the production of hepatocyte growth factor and M-CSF in HaCat cells, whereas at 0.2 mM, PDGF-AA and EPO were increased. The findings of this study suggest that mupirocin, which is commonly used as an antibacterial agent for the treatment of wounds, also facilitates the wound healing process by stimulating the proliferation of human keratinocytes and enhancing the production of several growth factors involved in wound healing. This is the first report on the effect of mupirocin on growth factors expressed by human keratinocytes as well as the stimulation of keratinocyte proliferation.

The In Vivo Quantitative Assessment of the Effectiveness of Low-Dose Photodynamic Therapy on Wound Healing Using Optical Coherence Tomography

The effect of low-dose photodynamic therapy on in vivo wound healing was investigated using optical coherence tomography. This work aims to develop an approach to quantitative assessment of the wound's state during wound healing including the effect of low-dose photodynamic therapy using topical application of two different photosensitizers, 5-aminolevulinic acid and methylene blue, and two laser doses of 1 J/cm2 and 4 J/cm2. It was concluded that the laser dose of 4 J/cm2 was better compared to 1 J/cm2 and allowed the wound healing process to accelerate.

Optical property recovery with spatially-resolved diffuse reflectance at short source-detector separations using a compact fiber-optic probe

We describe a compact fiber-optic probe (2 mm outside diameter) that utilizes spatially-resolved diffuse reflectance for tissue optical property recovery. Validation was performed in phantoms containing Intralipid 20% as scatterer, and methylene blue (MB), MnTPPS, and/or India ink as absorbers. Over a range of conditions, the reduced scattering coefficient was recovered with a root mean square error (RMSE) of 0.86-2.7 cm^-1 (average error = 3.8%). MB concentration was recovered with RMSE = 0.26-0.52 µM (average error = 15.0%), which did not vary with inclusion of MnTPPS (p=0.65). This system will be utilized to determine optical properties in human abscesses, in order to generate treatment plans for photodynamic therapy.

The Potentials of Methylene Blue as an Anti-Aging Drug

Methylene blue (MB), as the first fully man-made medicine, has a wide range of clinical applications. Apart from its well-known applications in surgical staining, malaria, and methemoglobinemia, the anti-oxidative properties of MB recently brought new attention to this century-old drug. Mitochondrial dysfunction has been observed in systematic aging that affects many different tissues, including the brain and skin. This leads to increaseding oxidative stress and results in downstream phenotypes under age-related conditions. MB can bypass Complex I/III activity in mitochondria and diminish oxidative stress to some degree. This review summarizes the recent studies on the applications of MB in treating age-related conditions, including neurodegeneration, memory loss, skin aging, and a premature aging disease, progeria.

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

Photodynamic Therapy Combined with Antibiotics or Antifungals against Microorganisms That Cause Skin and Soft Tissue Infections: A Planktonic and Biofilm Approach to Overcome Resistances

The present review covers combination approaches of antimicrobial photodynamic therapy (aPDT) plus antibiotics or antifungals to attack bacteria and fungi in vitro (both planktonic and biofilm forms) focused on those microorganisms that cause infections in skin and soft tissues. The combination can prevent failure in the fight against these microorganisms: antimicrobial drugs can increase the susceptibility of microorganisms to aPDT and prevent the possibility of regrowth of those that were not inactivated during the irradiation; meanwhile, aPDT is effective regardless of the resistance pattern of the strain and their use does not contribute to the selection of antimicrobial resistance. Additive or synergistic antimicrobial effects in vitro are evaluated and the best combinations are presented. The use of combined treatment of aPDT with antimicrobials could help overcome the difficulty of fighting high level of resistance microorganisms and, as it is a multi-target approach, it could make the selection of resistant microorganisms more difficult.