Wound Infection Model Research Articles

Rapid detection of microorganisms in a fish infection microfluidics platform

Inadequate access to clean water is detrimental to human health and aquatic industries. Waterborne pathogens can survive prolonged periods in aquatic bodies, infect commercially important seafood, and resist water disinfection, resulting in human infections. Environmental agencies and research laboratories require a relevant, portable, and cost-effective platform to monitor microbial pathogens and assess their risk of infection on a large scale. Advances in microfluidics enable better control and higher precision than traditional culture-based pathogen monitoring approaches. We demonstrated a rapid, high-throughput fish-based teleost (fish)-microbe (TelM) microfluidic-based device that simultaneously monitors waterborne pathogens in contaminated waters and assesses their infection potential under well-defined settings. A chamber-associated port allows direct access to the animal, while the transparency of the TelM platform enables clear observation of sensor readouts. As proof-of-concept, we established a wound infection model using Pseudomonas aeruginosa-contaminated water in the TelM platform, where bacteria formed biofilms on the wound and secreted a biofilm metabolite, pyoverdine. Pyoverdine was used as fluorescent sensor to correlate P. aeruginosa contamination to infection. The TelM platform was validated with environmental waterborne microbes from marine samples. Overall, the TelM platform can be readily applied to assess microbial and chemical risk in aquatic bodies in resource-constrained settings.

Liquid crystal nanoparticle platform for increased efficacy of cationic antimicrobials against biofilm infections

Bacterial biofilm infections tolerate high concentrations of antibiotics and are insidiously challenging to treat. Liquid crystal nanoparticles (LCNPs) advance the efficacy of tobramycin in biofilm-related infections by increasing the penetration of antibiotics across the biofilm matrix. Herewith, we develop the LCNPs as a platform technology, demonstrating that the LCNPs can increase the efficacy of two antibiotic classes (i.e. aminoglycosides and colistin) in P. aeruginosa biofilm infections. In C. elegans, the LCNPs potentiated the antimicrobial effect and significantly improved the survival of the nematodes. In mice with a full-thickness excisional wound, LCNPs were non-toxic and did not impair wound repair. Compared to the unformulated antibiotic treatment, tobramycin-LCNPs reduced the chronic bacterial load by 100-fold in the wound. This was also emulated in an ex vivo P. aeruginosa porcine wound infection model. The LCNPs represent a versatile platform technology that improves the efficacy of cationic antibiotics against biofilm infections utilizing multiple administration routes.

Development of a reproducible porcine model of infected burn wounds.

Severe burns are traumatic and physically debilitating injuries with a high rate of mortality. Bacterial infections often complicate burn injuries, which presents unique challenges for wound management and improved patient outcomes. Currently, pigs are used as the gold standard of pre-clinical models to study infected skin wounds due to the similarity between porcine and human skin in terms of structure and immunological response. However, utilizing this large animal model for wound infection studies can be technically challenging and create issues with data reproducibility. We present a detailed protocol for a porcine model of infected burn wounds based on our experience in creating and evaluating full thickness burn wounds infected with Staphylococcus aureus on six pigs. Wound healing kinetics and bacterial clearance were measured over a period of 27 d in this model. Enumerated are steps to achieve standardized wound creation, bacterial inoculation, and dressing techniques. Systematic evaluation of wound healing and bacterial colonization of the wound bed is also described. Finally, advice on animal housing considerations, efficient bacterial plating procedures, and overcoming common technical challenges is provided. This protocol aims to provide investigators with a step-by-step guide to execute a technically challenging porcine wound infection model in a reproducible manner. Accordingly, this would allow for the design and evaluation of more effective burn infection therapies leading to better strategies for patient care.

Chronic Wound Infection Model of Acinetobacter baumannii in Outbred Mice.

We established a murine wound infection model with doxycycline treatment against multidrug-resistant Acinetobacter baumannii (AB5075) in Institute of Cancer Research (ICR) outbred mice. Using three groups of neutropenic ICR mice, two full-thickness dorsal dermal wounds (6 mm diameter) were made on each mouse. In two groups, wounds were inoculated with 7.0 × 104 colony-forming units of AB5075. Of these two groups, one received a 6-day regimen of doxycycline while the other was sham treated with phosphate-buffered saline as placebo control. Another uninfected/untreated group served as a control. Wound closure, clinical symptoms, bacterial burden in wound beds and organs, and wound histology were investigated. Doxycycline-treated wounds completely healed by day 21, but untreated, infected wounds failed to heal. Compared to controls, wound infections without treatment resulted in significant reductions in body weight and higher bacterial loads in wound beds, lung, liver, and spleen by day 7. Histological evaluation of wounds on day 21 revealed ulcerated epidermis, muscle necrosis, and bacterial presence in untreated wounds, while wounds treated with doxycycline presented intact epidermis. Compared to the previously developed BALB/c dermal wound model, this study demonstrates that the mouse strain selected impacts wound severity and resolution. Furthermore, this mouse model accommodates two dorsal wounds rather than only one. These variations offer investigators increased versatility when designing future studies of wound infection. In conclusion, ICR mice are a viable option as a model of dermal wound infection. They accommodate two simultaneous dorsal wounds, and upon infection, these wounds follow a different pattern of resolution compared to BALB/c mice.

Synergistic Antimicrobial Effect of Lactiplantibacillus plantarum and Lawsonia inermis Against Staphylococcus aureus

PurposeThe developed resistance of pathogenic microorganisms towards the currently used antimicrobial agents requires the fast search for newer potent antimicrobials. One of the most important ways to combat the previously mentioned disaster is the use of natural alternatives like medicinal plants. Our study aimed to estimate the anti-inflammatory property, and antibacterial effects of probiotics Lactiplantibacillus plantarum and ethanol extracts of Lawsonia inermis leaves against Staphylococcus aureus when they were used separately or collectively as synergism.Material and MethodsExperimentally induced infected wound model in mice was created and divided into 10 groups then treated for two days by L. plantarum and L. inermis individually or in combination, followed by biochemical assays. The antibacterial, anti-inflammatory, and wound healing activity were evaluated through histopathological sections taken before and after treatment.ResultsOur results revealed that L. plantarum and L. inermis mixture could inhibit growth of S. aureus and decrease the minimal inhibitory concentration (MIC) of L. plantarum to 2 mg/mL. The mixture decreased level of both interleukin 6 (IL-6) and interferon-alpha (TNF-α) to a level near the normal uninfected group. Histopathological study showed that animals treated with both L. plantarum and L. inermis had achieved almost 90% healing.ConclusionThese results suggest that L. plantarum and L. inermis mixture has synergistic effect on healing of infected wound.

Controlled release of metal phenolic network protected phage for treating bacterial infection

Phage is a promising therapeutic agent for treating antibiotic resistant bacteria. However, in the process of treatment, phage may be cleared by the immune system and cleaved by protease, which could affect the efficacy of phage. In order to solve the above problems, phage encapsulation is usually adopted. In this study, we employed metal phenolic network (MPN) for efficient phage encapsulation which could protect phage from the cleavage of protease, and keep cytotoxicity weak. In the model of skin wound infection, the encapsulated phage could be released in response to pH change to achieve good antibacterial effect. Furthermore, the MPN encapsulation could prolong the T4 phage residence time at the wound. Our findings suggest that MPN can be a promising material for phage encapsulation.

Repurposing Eltrombopag as an Antimicrobial Agent Against Methicillin-Resistant Staphylococcus aureus.

Because of the excessive use of antibiotics, methicillin-resistant Staphylococcus aureus (MRSA) has become prevalent worldwide. Moreover, the formation of S. aureus biofilms often cause persistence and relapse of infections. Thus, the discovery of antibiotics with excellent antimicrobial and anti-biofilm activities is urgently needed. In the present study, eltrombopag (EP), a classic thrombopoietin receptor agonist, exhibited potential antimicrobial activity against S. aureus and its biofilms. Through our mechanistic studies, EP was found to interfere with proton motive force in S. aureus. The in vivo anti-infective efficacy of EP was further confirmed in the wound infection model, thigh infection model and peritonitis model by MRSA infection. In addition, the cytotoxicity of EP against mammalian cells and the in vivo toxicity of EP in animal models were not observed at the tested concentrations. Collectively, these results indicate that EP could be considered a potential novel antimicrobial agent against recalcitrant infections caused by MRSA.

Antioxidant and antibacterial phytate hydrogel for MRSA infected wound healing

Methicillin-resistant Staphylococcus aureus (MRSA) infected wound healing and repair is still a challenge. Herein, we developed an in situ-formed copper phytate nanoparticle-F127 hydrogel (FPSCu) with multifunctional properties for MRSA-infected wound treating. FPSCu hydrogel showed the injectability, temperature sensitivity, inherent antioxidant activity and high antibacterial activity against MRSA, as well as good biocompatibility. The MRSA infected wound model in mice showed that the FPSCu hydrogel could inhibit bacterial infection and accelerate wound healing. The facile preparation process and multifunctional bioactivities enable FPSCu the highly promising as the advanced dressing for wound repair.

In situ fabrication of metal-organic framework derived hybrid nanozymes for enhanced nanozyme-photothermal therapy of bacteria-infected wounds

In recent years, nanozyme-photothermal therapy (NPT) has attracted enormous interests owing to their enhanced therapeutic effects and less adverse effects in the treatment of infectious diseases. However, the development of nanozyme-photothermal agents (NPAs) that can rapidly, efficiently and synergistically combating pathogenic bacteria remains a huge challenge due to the limitation of size effect. Herein, by decorating platinum nanozymes on Zn-based photosensitizer, we report a novel metal-organic framework (MOF)-derived hybrid nanozymes antibacterial strategy for enhanced NPT. This strategy can not only prevent the aggregation of platinum nanozymes and effectively reduce the mass transfer resistance during the kinetic reaction, but also inhibit the photoelectron-hole recombination in the process of photothermal therapy (PTT) and improve the photothermal conversion performance. In the presence of a low concentration of hydrogen peroxide (H 2 O 2 ), the superior nanocatalytic activity of the MOF-derived hybrid nanozymes can effectively catalyze the release of H 2 O 2 to generate toxic hydroxyl radical (•OH), resulting in the increase of bacterial membrane permeability and thermal sensitivity. Once the near-infrared laser is introduced, the nanozyme-photothermal antibacterial platform can play the role of “nanoknife” to further induce the death of the damaged bacteria by physical cutting. In vitro and vivo in antibacterial assays confirm that the MOF-derived hybrid nanozymes have excellent antibacterial properties, which can serve as an antibacterial candidate with negligible adverse effect. Therefore, this work will open a new avenue for MOF-derived hybrid nanozymes in biomedical application. • The MOF-derived hybrid nanozymes antibacterial strategy was used to enhance the nanozyme-photothermal therapy. • The PEG@Zn/Pt–CN nanozyme-photothermal antibacterial platform processed excellent ROS-released and NIR-responsive property. • The PEG@Zn/Pt–CN nanozyme-photothermal antibacterial platform could kill 98.74% E. coli and 99.63% S. aureus. • Wound infection model experiments confirmed the antibacterial activity and the rapid tissue repair effect.

Development of Chitosan‐Assisted Fe3O4@SiO2 Magnetic Nanostructures Functionalized with Nisin as a Topical Combating System against Vancomycin‐Intermediate Staphylococcus aureus (VISA) Skin Wound Infection in Mice

The clinical significance of vancomycin‐intermediate S. aureus (VISA) infections is intensified by its tendency to develop resistance to antimicrobials and persistent infections. The decreasing effectiveness of the antimicrobials available is now seriously compromised; thus, there is an emergent need to invent new classes of antimicrobial agents that can rapidly and efficiently eradicate infections. Fe3O4@SiO2@chitosan (CS) nanocomposites were successfully synthesized and then decorated with nisin to gain Fe3O4/SiO2/CS/nisin‐based magnetic nanostructures (Fe3O4@SiO2@CS‐NISIN). The nanomaterials were characterized comparatively via FTIR (Fourier transform infrared spectroscopy), XRD (X‐ray diffraction), FE‐SEM (field emission scanning electron microscopes), DLS (dynamic light scattering), and VSM (vibrating sample magnetometer) methods. The methyl thiazol tetrazolium (MTT) assay was performed to determine the inhibitory effects of antibacterial agents on the cell viability. The in vitro bactericidal effect of all compounds was characterized using the microdilution assay. Finally, the topical antibacterial efficacy of free nisin, Fe3O4@SiO2@CS, and Fe3O4@SiO2@CS‐NISIN nanocomposites against murine superficial wound infection models was determined. The functionalized nanocomposites were more efficient in suppressing bacterial growth in vitro and in vivo compared to the same quantities of untargeted nanocomposites. MTT results showed acceptable biocompatibility of all nanoformulations, and no substantial difference in the cell viability was recorded between treated cells and untreated control. These results suggest that Fe3O4@SiO2@CS‐NISIN nanocomposites can be served as an alternative antimicrobial agent in innovative and emerging technologies to treat a variety of staphylococcal infections.

Therapeutic evaluation of immunomodulators in reducing surgical wound infection.

Despite many advances in infection control practices, including prophylactic antibiotics, surgical site infections (SSIs) remain a significant cause of morbidity, prolonged hospitalization, and death worldwide. Our innate immune system possesses a multitude of powerful antimicrobial strategies which make it highly effective in combating bacterial, fungal, and viral infections. However, pathogens use various stealth mechanisms to avoid the innate immune system, which in turn buy them time to colonize wounds and damage tissues at surgical sites. We hypothesized that immunomodulators that can jumpstart and activate innate immune responses at surgical sites, would likely reduce infection at surgical sites. We used three immunomodulators; fMLP (formyl-Methionine-Lysine-Proline), CCL3 (MIP-1α), and LPS (Lipopolysaccharide), based on their documented ability to elicit strong inflammatory responses; in a surgical wound infection model with Pseudomonas aeruginosa to evaluate our hypothesis. Our data indicate that one-time topical treatment with these immunomodulators at low doses significantly increased proinflammatory responses in infected and uninfected surgical wounds and were as effective, (or even better), than a potent prophylactic antibiotic (Tobramycin) in reducing P. aeruginosa infection in wounds. Our data further show that immunomodulators did not have adverse effects on tissue repair and wound healing processes. Rather, they enhanced healing in both infected and uninfected wounds. Collectively, our data demonstrate that harnessing the power of the innate immune system by immunomodulators can significantly boost infection control and potentially stimulate healing. We propose that topical treatment with these immunomodulators at the time of surgery may have therapeutic potential in combating SSI, alone or in combination with prophylactic antibiotics.

Topical Administration of an Ointment Prepared From Satureja sahendica Essential Oil Accelerated Infected Full-Thickness Wound Healing by Modulating Inflammatory Response in a Mouse Model

Satureja sahendica has antibacterial and anti-inflammatory properties that can have beneficial effects for decreasing inflammation in infected wounds. This study was conducted to evaluate the effects of an ointment prepared from S sahendica essential oil (SSO) on an infected wound model in BALB/c mice. One full-thickness excisional skin wound was surgically created per animal and inoculated with 5 × 107 colony-forming units of Pseudomonas aeruginosa and Staphylococcus aureus. Following induction of the wound, the mice (N = 90) were treated with soft yellow paraffin (negative control, n = 18), mupirocin (positive control, n = 18) and 1%, 2%, and 4% SSO (n = 18 in each of the 3 groups). To determine the effect of the treatments on healing of an infected wound, the following factors were assessed: rate of the wound area, tissue bacterial count, histopathology, collagen biosynthesis, immunohistochemistry, and the expressions of insulin-like growth factor (IGF)-1, fibroblast growth factor (FGF)-2, vascular endothelial growth factor (VEGF), interleukin (IL)-1ß, IL-4, transforming growth factor beta (TGF-ß), and chemokine (CXC motif) ligand 1 (CXCL-1) on days 3, 7, and 14 after induction of the wound. Topical administration of SSO shortened the inflammatory phase, accelerated cellular proliferation, and increased fibroblast distribution per 1 mm2, collagen deposition, and rapid reepithelialization in comparison with control animals (P <.05). The messenger RNA levels of IGF-1, IL-10, FGF-2, VEGF, TGF-ß1, and CXCL-1 were remarkably increased, and IL-1ß level decreased (P <.05) in the treated animals compared with the control group (P <.05). The immunohistochemical analyses showed topical administration of SSO increased collagen biosynthesis in the treated group (P <.05). Topical administration of SSO shows evidence of accelerating wound healing by upregulating the expression of IGF-1, IL-10, FGF-2, VEGF, TGF-ß, and CXCL-1; shortening the inflammatory stage; and promoting the proliferative phase.

Dextran and peptide-based pH-sensitive hydrogel boosts healing process in multidrug-resistant bacteria-infected wounds

Traumatic multidrug-resistant (MDR) bacterial infections are deadly threat to the public. To combat MDR bacteria, we developed a dual functional pH-sensitive hydrogel based on peptide DP7 (VQWRIRVAVIRK) and oxidized dextran (DP7-ODEX hydrogel). As an antimicrobial peptide, DP7 can synergize with many antibiotics; thus, we loaded ceftazidime into DP7-ODEX hydrogel, which showed an obvious advantage in MDR P. aeruginosa inhibition. Additionally, due to the interaction between aldehyde groups in oxidized dextran and amine groups from wound tissue, the hydrogel could extend on the irregular surface of skin defects and promote epithelial cells adhesion. DP7 could also be used as a wound-healing peptide and accelerate the healing process. We confirmed that the DP7-ODEX hydrogel exerted formidable therapeutic effects in normal or diabetic wound infection model. According to histomorphology analysis we found that DP7 hydrogel also have a scarless wound healing ability. In summary, we developed a hydrogel fabricated by the dual functional peptide DP7 that can kill multidrug-resistant bacteria colonizing the wound bed and boost scarless wound healing.

Sanguiin H-6 Fractionated from Cloudberry (Rubus chamaemorus) Seeds Can Prevent the Methicillin-Resistant Staphylococcus aureus Biofilm Development during Wound Infection.

Staphylococcus aureus is the most common cause of surgical site infections and its treatment is challenging due to the emergence of multi-drug resistant strains such as methicillin-resistant S. aureus (MRSA). Natural berry-derived compounds have shown antimicrobial potential, e.g., ellagitannins such as sanguiin H-6 and lambertianin C, the main phenolic compounds in Rubus seeds, have shown antimicrobial activity. The aim of this study was to evaluate the effect of sanguiin H-6 and lambertianin C fractionated from cloudberry seeds, on the MRSA growth, and as treatment of a MRSA biofilm development in different growth media in vitro and in vivo by using a murine wound infection model where sanguiin H-6 and lambertianin C were used to prevent the MRSA infection. Sanguiin H-6 and lambertianin C inhibited the in vitro biofilm development and growth of MRSA. Furthermore, sanguiin H-6 showed significant anti-MRSA effect in the in vivo wound model. Our study shows the possible use of sanguiin H-6 as a preventive measure in surgical sites to avoid postoperative infections, whilst lambertianin C showed no anti-MRSA activity.

Continuous and controllable electro-fabrication of antimicrobial copper-alginate dressing for infected wounds treatment

The contamination of chronic wound with bacteria especially methicillin-resistant Staphylococcus aureus (MRSA) is considered as the major factor interferencing normal wound healing. There still remain great challenges in developing safe and effective wound dressings with wide-spectrum antibacterial functions. Alginate hydrogel is a common dressing for wound treatment. Copper is one of the trace elements in human body with inherent antibacterial activity. Traditional methods for preparing a structure-controlled copper-alginate antibacterial matrix are difficult however, due to the fast and uncontrolled gelation between alginate and metal ions. In this work, we report an electrodeposition method for rapid fabrication of copper cross-linked alginate antibacterial films (Cu2+-Alg) with controlled structure and copper content, which is relied on an electrical signal controlled release of copper ions from the reaction of insoluble salt Cu2(OH)2CO3 and the generated protons via water electrolysis on anode. The results prove that the physical structure and chemical composition of the electrodeposited Cu2+-Alg films can be continuously modulated by the imposed charges during electrodeposition. In vitro tests demonstrate the film has Cu2+ content-dependent bactericidal activities. Film’s cytocompatibility is well controlled by the imposed charges for Cu2+-Alg fabrication. The MRSA infected wound model in vivo also indicates that Cu2+-Alg film can effectively eliminate bacterial infection and suppress host inflammatory responses. We believe this study demonstrates a convenient and controllable strategy to fabricate alginate antibacterial dressings with potential applications for infected wound treatment. More broadly, our work reveals electrodeposition is a general and simple platform to design alginate films with versatile functions.

Rational synthesis of Three-Layered plasmonic nanocomposites of copper Sulfide/Gold/Zinc-Doped Prussian blue analogues for improved photothermal disinfection and wound healing

Bacteria-infected wounds have imposed serious challenges in human health whereas the abuse of antibiotics makes bacteria drug-resistant and becoming more and more difficult to deal with. Herein, we developed a drug-free three-layered photothermal bactericide from inside to outside consisting of copper sulfide (CuS), gold (Au) and zinc-doped Prussian blue analogues (ZnPBA) (named as CuS@Au@ZnPBA). The CuS@Au@ZnPBA was demonstrated to possess remarkably-improved photothermal property and excellent biosafety. Local heat generated by CuS@Au@ZnPBA under the irradiation of 808 nm laser enables efficient bacteria ablation in vitro and in a mouse model of cutaneous wound infection. Meanwhile, the released zinc ions (Zn2+) could upregulate the genes involved in collagen deposition to accelerate wound healing. Overall, the finely-designed nanocomposites can serve as a promising kind of antibacterial alternative to current antibiotic therapies against bacterial wound infections.

Addressing MRSA infection and antibacterial resistance with peptoid polymers

Methicillin-Resistant Staphylococcus aureus (MRSA) induced infection calls for antibacterial agents that are not prone to antimicrobial resistance. We prepare protease-resistant peptoid polymers with variable C-terminal functional groups using a ring-opening polymerization of N-substituted N-carboxyanhydrides (NNCA), which can provide peptoid polymers easily from the one-pot synthesis. We study the optimal polymer that displays effective activity against MRSA planktonic and persister cells, effective eradication of highly antibiotic-resistant MRSA biofilms, and potent anti-infectious performance in vivo using the wound infection model, the mouse keratitis model, and the mouse peritonitis model. Peptoid polymers show insusceptibility to antimicrobial resistance, which is a prominent merit of these antimicrobial agents. The low cost, convenient synthesis and structure diversity of peptoid polymers, the superior antimicrobial performance and therapeutic potential in treating MRSA infection altogether imply great potential of peptoid polymers as promising antibacterial agents in treating MRSA infection and alleviating antibiotic resistance.

Identification of microbes in wounds using near-infrared spectroscopy

BackgroundRapid diagnosis of microbes in the burn wound is a big challenge in the medical field. Traditional biochemical detection techniques take hours or days to identify the species of contaminating and drug-resistant microbes. Near-infrared spectroscopy (NIRS) is evaluated to address the need for a fast and sensitive method for the detection of bacterial contamination in liquids. MethodsHerin, we developed a novel technique which by using NIRS together with supporting vector machine (SVM), to identify the microbial species and drug-resistant microbes in LB medium, and to diagnose the wound colonization and wound infection models of pigs. ResultsThe device could recognize 100% of seven kinds of microbes and 99.47% of the multi-drug resistant Staphylococcus aureus (S. aureus), with a concentration of 109 cfu ml−1 in LB medium. The accuracy of the microbial identification in colonized and infected wounds in-situ was 100%. The detection limit of NIRS with SVM for the detection of S. aureus and Escherichia coli (E. coli) was 101 cfu ml−1 in LB medium. Identification time was less than 5 s. ConclusionOur findings validate for the first time a novel technique aimed at the rapid, noncontacted, highly sensitive, and specific recognition of several microbial species including drug-resistant ones. This technique could represent a promising approach to identify diverse microbial species and a potential bedside device to rapidly diagnose infected wounds.

Polymyxin B-Triggered Assembly of Peptide Hydrogels for Localized and Sustained Release of Combined Antimicrobial Therapy.

Repurposing old antibiotics into more effective and safer formulations is an emergent approach to tackle the growing threat of antimicrobial resistance. Herein, a peptide hydrogel is reported for the localized and sustained release of polymyxin B (PMB), a decade-old antibiotic with increasing clinical utility for treating multidrug-resistant Gram-negative bacterial infections. The hydrogel is assembled by additing PMB solution into a rationally designed peptide amphiphile (PA) solution and its mechanical properties can be adjusted through the addition of counterions, envisioning its application in diverse infection scenarios. Sustained release of PMB from the hydrogel over a 5-day period and prolonged antimicrobial activities against Gram-negative bacteria are observed. The localized release of active PMB from the hydrogel is shown to be effective in vivo for treating Pseudomonas aeruginosa infection in the Galleria mellonella burn wound infection model, dramatically reducing the mortality from 93% to 13%. Complementary antimicrobial activity against Gram-positive Staphylococcus aureus and enhanced antimicrobial effect against the Gram-negative Acinetobacter baumannii are observed when an additional antibiotic fusidic acid is incorporated into the hydrogen network. These results demonstrate the potential of the PMB-triggered PA hydrogel as a versatile platform for the localized and sustained delivery of combined antimicrobial therapies.

Hypericin and Pheophorbide a Mediated Photodynamic Therapy Fighting MRSA Wound Infections: A Translational Study from In Vitro to In Vivo.

High prevalence rates of methicillin-resistant Staphylococcus aureus (MRSA) and lack of effective antibacterial treatments urge discovery of alternative therapeutic modalities. The advent of antibacterial photodynamic therapy (aPDT) is a promising alternative, composing rapid, nonselective cell destruction without generating resistance. We used a panel of clinically relevant MRSA to evaluate hypericin (Hy) and pheophobide a (Pa)-mediated PDT with clinically approved methylene blue (MB). We translated the promising in vitro anti-MRSA activity of selected compounds to a full-thick MRSA wound infection model in mice (in vivo) and the interaction of aPDT innate immune system (cytotoxicity towards neutrophils). Hy-PDT consistently displayed lower minimum bactericidal concentration (MBC) values (0.625–10 µM) against ATCC RN4220/pUL5054 and a whole panel of community-associated (CA)-MRSA compared to Pa or MB. Interestingly, Pa-PDT and Hy-PDT topical application demonstrated encouraging in vivo anti-MRSA activity (>1 log10 CFU reduction). Furthermore, histological analysis showed wound healing via re-epithelization was best in the Hy-PDT group. Importantly, the dark toxicity of Hy was significantly lower (p < 0.05) on neutrophils compared to Pa or MB. Overall, Hy-mediated PDT is a promising alternative to treat MRSA wound infections, and further rigorous mechanistic studies are warranted.