Preclinical evaluation of a novel silver gelling fiber dressing on Pseudomonas aeruginosa in a porcine wound infection model

An Antimicrobial Blue Light Prototype Device Controls Infected Wounds in a Preclinical Porcine Model

We developed a translational prototype antimicrobial blue light (ABL) device for treating skin wounds with ABL. Partial-thickness surgical wounds were created in live swine (an animal whose skin is considered the most like human skin), then heavily contaminated and left untreated for 24 hours with methicillin-resistant Staphylococcus aureus (MRSA). ABL treatment stabilized and reduced MRSA infection by greater than 4 orders of magnitude (>99.99%; P < .0001) compared with untreated wounds in the same animal, after only 2 daily treatments. These data support further development of such devices for controlling infection in skin wounds. ABL, with or without concomitant administration of negative pressure, antimicrobials, or photosensitizers, could play an important role in modern wound care by reducing the amount, duration, and cost of antibiotics needed, helping reduce antimicrobial resistance. No such device for treating human cutaneous wounds currently exists. This deserves further development and study.

Clinical management of chronic wound infections: The battle against biofilm

Bacteria constitute the most abundant life form on earth, of which the majority exist in a protective biofilm state. Since the 1980s, we have learned much about the role of biofilm in human chronic infections, with associated global healthcare costs recently estimated at ~$386 billion. Chronic wound infection is a prominent biofilm-induced condition that is characterised by persistent inflammation and associated host tissue destruction, and clinical signs that are distinct from signs of acute wound infection. Biofilm also enables greater tolerance to antimicrobial agents in chronic wound infections compared with acute wound infections. Given the difficulty in eliminating wound biofilm, a multi-targeted strategy (namely biofilm-based wound care) involving debridement and antimicrobial therapies were introduced and have been practiced since the early 2000s. More recently, acknowledgement of the speed at which biofilm can develop and hence quickly interfere with wound healing has highlighted the need for an early anti-biofilm strategy to combat biofilm before it takes control and prevents wound healing. This strategy, referred to as wound hygiene, involves multiple tools in combination (debridement, cleansing, and antimicrobial dressings) to maximise success in biofilm removal and encourage wound healing. This review is intended to highlight the issues and challenges associated with biofilm-induced chronic infections, and specifically address the challenges in chronic wound management, and tools required to combat biofilm and encourage wound healing.

The efficacy of a nitric oxide-releasing formulation on nares isolated Methicillin-Resistant Staphylococcus aureus in porcine wound infection model

Background

The colonization of Staphylococcus aureus (SA) acquired in nosocomial infections may develop acute and chronic infections such as Methicillin-Resistant Staphylococcus aureus (MRSA) in the nose. As a commensal microorganism with the ability to form a biofilm, SA can dwell on the skin, nostrils, throat, perineum, and axillae of healthy humans. Nitric oxide (NO) is an unstable gas with various molecular functions and has antimicrobial properties which are converted into many potential treatments.

Methods

Methicillin-Resistant Staphylococcus aureus MRSA BAA1686 isolated from nasal infection was used in a porcine wound infection model. Deep partial-thickness wounds (10mm x 7mm x 0.5mm) were made on three animals using a specialized electrokeratome. All wounds were inoculated and then covered with polyurethane film dressings for biofilm formation. After 48 hours, three wounds were recovered from each animal for baseline enumeration. The remaining wounds were randomly assigned to six treatment groups and treated once daily. The treatment groups are as follows: NO topical ointments concentrations of 0.3, 0.9 and 1.8%, Vehicle Ointment, Mupirocin 2%, and Untreated Control. Microbiological recoveries were conducted on day 4 and day 7.

Results

The greatest efficacy observed from the NO formulations against MRSA BAA1686 was the 1.8% concentration. This agent was able to reduce more than 99% of bacterial counts when compared to Baseline, Vehicle Ointment, and Untreated Control wounds on both assessment days. Mupirocin 2% was the overall best treatment against MRSA BAA1686 on both assessment days, with a significant reduction (p ≤ 0.05) of 4.70 ± 0.13 Log CFU/mL from day 4 to day 7.

Conclusions

Overall, the positive control Mupirocin 2% was the most effective in eliminating MRSA BAA1686 throughout the study. This experiment demonstrated a downward trend from the highest concentration of NO topical ointment formulations to the lowest concentrations on both assessment days (0.3% - 1.8%). Out of all NO topical ointments, the highest concentration (1.8%) was the most effective with the potential to be an alternative treatment against a MRSA nasal strain biofilm.

Effectiveness of a polyhexamethylene biguanide-containing wound cleansing solution using experimental biofilm models

OBJECTIVE

Antiseptics are widely used in wound management to prevent or treat wound infections, and have been shown to have antibiofilm efficacy. The objective of this study was to assess the effectiveness of a polyhexamethylene biguanide (PHMB)-containing wound cleansing and irrigation solution on model biofilm of pathogens known to cause wound infections compared with a number of other antimicrobial wound cleansing and irrigation solutions.

METHOD

Staphylococcus aureus and Pseudomonas aeruginosa single-species biofilms were cultured using microtitre plate and Centers for Disease Control and Prevention (CDC) biofilm reactor methods. Following a 24-hour incubation period, the biofilms were rinsed to remove planktonic microorganisms and then challenged with wound cleansing and irrigation solutions. Following incubation of the biofilms with a variety of concentrations of the test solutions (50%, 75% or 100%) for 20, 30, 40, 50 or 60 minutes, remaining viable organisms from the treated biofilms were quantified.

RESULTS

The six antimicrobial wound cleansing and irrigation solutions used were all effective in eradicating Staphylococcus aureus biofilm bacteria in both test models. However, the results were more variable for the more tolerant Pseudomonas aeruginosa biofilm. Only one of the six solutions (sea salt and oxychlorite/NaOCl-containing solution) was able to eradicate Pseudomonas aeruginosa biofilm using the microtitre plate assay. Of the six solutions, three (a solution containing PHMB and poloxamer 188 surfactant, a solution containing hypochlorous acid (HOCl) and a solution containing NaOCl/HOCl) showed increasing levels of eradication of Pseudomonas aeruginosa biofilm microorganisms with increasing concentration and exposure time. Using the CDC biofilm reactor model, all six cleansing and irrigation solutions, except for the solution containing HOCl, were able to eradicate Pseudomonas aeruginosa biofilms such that no viable microorganisms were recovered.

CONCLUSION

This study demonstrated that a PHMB-containing wound cleansing and irrigation solution was as effective as other antimicrobial wound irrigation solutions for antibiofilm efficacy. Together with the low toxicity, good safety profile and absence of any reported acquisition of bacterial resistance to PHMB, the antibiofilm effectiveness data support the alignment of this cleansing and irrigation solution with antimicrobial stewardship (AMS) strategies.

Vitamin K3 (Menadione) is a multifunctional microbicide acting as a photosensitizer and synergizing with blue light to kill drug-resistant bacteria in biofilms

Cutaneous bacterial wound infections typically involve gram-positive cocci such as Staphylococcus aureus (SA) and usually become biofilm infections. Bacteria in biofilms may be 100-1000-fold more resistant to an antibiotic than the clinical laboratory minimal inhibitory concentration (MIC) for that antibiotic, contributing to antimicrobial resistance (AMR). AMR is a growing global threat to humanity. One pathogen-antibiotic resistant combination, methicillin-resistant SA (MRSA) caused more deaths globally than any other such combination in a recent worldwide statistical review. Many wound infections are accessible to light. Antimicrobial phototherapy, and particularly antimicrobial blue light therapy (aBL) is an innovative non-antibiotic approach often overlooked as a possible alternative or adjunctive therapy to reduce antibiotic use. We therefore focused on aBL treatment of biofilm infections, especially MRSA, focusing on in vitro and ex vivo porcine skin models of bacterial biofilm infections. Since aBL is microbicidal through the generation of reactive oxygen species (ROS), we hypothesized that menadione (Vitamin K3), a multifunctional ROS generator, might enhance aBL. Our studies suggest that menadione can synergize with aBL to increase both ROS and microbicidal effects, acting as a photosensitizer as well as an ROS recycler in the treatment of biofilm infections. Vitamin K3/menadione has been given orally and intravenously worldwide to thousands of patients. We conclude that menadione/Vitamin K3 can be used as an adjunct to antimicrobial blue light therapy, increasing the effectiveness of this modality in the treatment of biofilm infections, thereby presenting a potential alternative to antibiotic therapy, to which biofilm infections are so resistant.

Tryptone-stabilized silver nanoparticles' potential to mitigate planktonic and biofilm growth forms of Serratia marcescens

Several microbial pathogens are capable of forming biofilms. These microbial communities pose a serious challenge to the healthcare sector as they are quite difficult to combat. Given the challenges associated with the antibiotic-based management of biofilms, the research focus has now been shifted towards finding alternate treatment strategies that can replace or complement the antibacterial properties of antibiotics. The field of nanotechnology offers several novel and revolutionary approaches to eradicate biofilm-forming microbes. In this study, we evaluated the antibacterial and antibiofilm efficacy of in-house synthesized, tryptone-stabilized silver nanoparticles (Ts-AgNPs) against the superbug Serratia marcescens. The nanoparticles were of spherical morphology with an average hydrodynamic diameter of 170 nm and considerable colloidal stability with a Zeta potential of - 24 ± 6.15 mV. Ts-AgNPs showed strong antibacterial activities with a minimum inhibitory concentration (MIC₅₀) of 2.5 µg/mL and minimum bactericidal concentration (MBC) of 12.5 µg/mL against S. marcescens. The nanoparticles altered the cell surface hydrophobicity and inhibited biofilm formation. The Ts-AgNPs were also effective in distorting pre-existing biofilms by degrading the extracellular DNA (eDNA) component of the extracellular polymeric substance (EPS) layer. Furthermore, reduction in quorum-sensing (QS)-induced virulence factors produced by S. marcescens indicated that Ts-AgNPs attenuated the QS pathway. Together, these findings suggest that Ts-AgNPs are an important anti-planktonic and antibiofilm agent that can be explored for both the prevention and treatment of infections caused by S. marcescens.

Biofilm model on mice skin wounds

PURPOSE

To evaluate a biofilm model of Pseudomonas aeruginosa in excisional cutaneous wound in mice.

METHODS

Preclinical, translational study conducted with 64 C57BL/6 mice randomly assigned to control and intervention groups. Evaluation was on days D0, D3, D5, D7 and D10 of wound making. The profile of biofilm formation and induction was evaluated using wound closure kinetics, quantitative culture, and evaluation of wounds using transmission electron microscopy (TEM). Clinical evaluation was performed by liver tissue culture, weight variation, and quantification of leukocytes in peripheral blood. Analyses were performed with GraphPad Prism software.

RESULTS

Bacterial load for induction of infection with P. aeruginosa and survival of animals was 104 UFC·mL-1. In D5 (p < 0.0001) and D7 (p < 0.01), animals in the intervention group showed a delay in the healing process and had their wounds covered by necrotic tissue until D10. Statistical differences were observed in wound cultures and weight at D5 and D7 (p < 0.01). Liver cultures and leukocyte quantification showed no statistical differences. No bacteria in planktonic or biofilm form were identified by TEM.

CONCLUSIONS

The findings raise questions about the understanding of the ease of formation and high occurrence of biofilm in chronic wounds.

The performance of gelling fibre wound dressings under clinically relevant robotic laboratory tests

The effectiveness of wound dressing performance in exudate management is commonly gauged in simple, non‐realistic laboratory setups, typically, where dressing specimens are submersed in vessels containing aqueous solutions, rather than by means of clinically relevant test configurations. Specifically, two key fluid–structure interaction concepts: sorptivity—the ability of wound dressings to transfer exudate, including viscous fluids, away from the wound bed by capillary action and durability—the capacity of dressings to maintain their structural integrity over time and particularly, at removal events, have not been properly addressed in existing test protocols. The present article reviews our recent published research concerning the development of clinically relevant testing methods for wound dressings, focussing on the clinical relevance of the tests as well as on the standardisation and automation of laboratory measurements of dressing performance. A second objective of this work was to compile the experimental results characterising the performance of gelling fibre dressings, which were acquired using advanced testing methods, to demonstrate differences across products that apparently belong to the same “gelling fibre” family but differ remarkably in materials, structure and composition and, thereby, in performance.

Candida albicans Infections: a novel porcine wound model to evaluate treatment efficacy

Candida albicans is a common cause of opportunistic mycoses worldwide and a major contributor in wound infections. The purpose of this study was to establish a fungal wound model and analyze the effects of a common antifungal agent against the proliferation of three C. albicans strains. Second degree burns were created, and then inoculated with one of three different C. albicans ATCC strains: 10261 reference strain, 64550 fluconazole resistant and 26310 fluconazole sensitive. After fungal inoculation, every wound was covered with dressings for 4 h to allow fungal colonization on every wound bed. After 4 h, the dressings were removed, and each wound was treated either once or twice daily with a topical terbinafine hydrochloride or left untreated. On days 2, 4 and 7 post inoculation, three wounds from each treatment group were scrub cultured and quantified. On day 2, wounds infected with the sensitive strains 26310 and 10261 and treated twice showed a significant reduction when compared against those infected wounds receiving once daily treatment. On day 4, wounds which were infected with C. albicans fluconazole sensitive (ATCC 26310) showed a significant reduction in fungal cell counts with treatment applied twice daily. A significant reduction in the colony counts was exhibited in all three strains at the seventh day with active as compared to the non-treated wounds. Twice daily treatment resulted in a lower fungal count than once daily treatment. Neither treatment was able to entirely eradicate C. albicans during the duration of this study. Establishing a reliable fungal wound model will help in the translational goal of identifying new antifungal that could be used clinically by wound care providers.

A novel dressing with silver to treat meticillin-resistant Staphylococcus aureus biofilm infection in a pig model

OBJECTIVE

The purpose of this study was to use an in vivo biofilm porcine model to examine a new polyvinyl alcohol-based gelling fibre dressing with silver and compare it to other commercial dressings containing: polyvinyl alcohol-based gelling fibre without silver; carboxymethyl cellulose-based fibre with silver, benzethonium chloride and ethylenediaminetetraacetic acid; and untreated control.

METHODS

A total of 52 deep partial-thickness wounds (10x7x0.5mm) were created on each of three animals and inoculated with 25µl of meticillin-resistant Staphylococcus aureus (MRSA) (10⁶ colony forming units (CFU)/ml). Wounds were covered for 24 hours to allow biofilm formation and were randomly designated to one of the four treatments. Samples were recovered for microbiological and histological analysis on days 3, 5 and 7 post-treatment.

RESULTS

Polyvinyl alcohol-based gelling fibre dressing with silver was able to significantly reduce biofilm more effectively than the other treatment groups. By day 7, wounds treated with the dressing had a 2.72±0.01 log CFU/g reduction in MRSA count versus untreated control wounds and a 2.59±0.01 log CFU/g reduction versus baseline counts. For histology analysis, all wounds reached 100% re-epithelialisation by day 5.

CONCLUSION

The results of this study indicated that polyvinyl alcohol-based gelling fibre dressing with silver was effective against biofilm of antibiotic-resistant staphylococcal strains without inhibiting the wound healing process, and may have important clinical implications when treating acute and/or hard-to-heal wounds.

Antimicrobial effectiveness of wound matrices containing native extracellular matrix with polyhexamethylene biguanide

A variety of wound matrix materials that are designed to help heal both acute and chronic wounds are currently available. Because wounds often encounter opportunistic microbes that can delay healing, the effectiveness of these materials is often suboptimal, resulting in delayed or compromised wound healing. The importance of reducing and controlling wound microbes is well recognised and there are several antimicrobial options available to address this unmet clinical need. This study compares the antimicrobial and wound healing capabilities, both in vivo and in vitro against methicillin-resistant Staphylococcus aureus (MRSA) USA 300, for the following compounds: Collagen Wound Matrix-Anti Microbial (CWM-AM); Collagen Wound Matrix-Anti Microbial XT (CWM-AM XT); Antimicrobial Hydrofiber Wound Dressing (AHWD); Dermal Scaffold with Silver (DRSAg); Collagen Extracellular Matrix (CEM); Collagen Wound Matrix (CWM); Matrix Wound Dressing with Silver (MWDAg); Cadexomer Iodine Gel (CIG); Triple Antibiotic Ointment (TAO); and Antimicrobial Wound Gel (AWG). For the in vitro zone of inhibition assay, AWG and CIG had the largest diffused areas, followed by CWM-AM and CWM-AM XT. Furthermore, CWM-AM, CWM-AM XT, AWG, and CIG exhibited a persistent antimicrobial activity for up to 10 days after incubation. However, in the cytotoxicity studies performed using human fibroblasts, CWM-AM and CWM-AM XT had no detrimental effects in cell proliferation and viability, while AWG and CIG were cytotoxic and prohibitive for cell proliferation. Treatments were then assessed for microbiology and wound healing efficacy using an in vivo porcine deep reticular dermal wound model. CWM-AM XT displayed the greatest in vivo antimicrobial activity against MRSA USA300 and expedited the reepithelialisation at a faster rate than other treatment groups. This study shows that a novel collagen matrix containing an antimicrobial agent can reduce the bacterial load and support healing.

Biofilm Management in Wound Care

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand the basics of biofilm infection and be able to distinguish between planktonic and biofilm modes of growth. 2. Have a working knowledge of conventional and emerging antibiofilm therapies and their modes of action as they pertain to wound care. 3. Understand the challenges associated with testing and marketing antibiofilm strategies and the context within which these strategies may have effective value.

SUMMARY

The Centers for Disease Control and Prevention estimate for human infectious diseases caused by bacteria with a biofilm phenotype is 65 percent and the National Institutes of Health estimate is closer to 80 percent. Biofilms are hostile microbial aggregates because, within their polymeric matrix cocoons, they are protected from antimicrobial therapy and attack from host defenses. Biofilm-infected wounds, even when closed, show functional deficits such as deficient extracellular matrix and impaired barrier function, which are likely to cause wound recidivism. The management of invasive wound infection often includes systemic antimicrobial therapy in combination with débridement of wounds to a healthy tissue bed as determined by the surgeon who has no way of visualizing the biofilm. The exceedingly high incidence of false-negative cultures for bacteria in a biofilm state leads to missed diagnoses of wound infection. The use of topical and parenteral antimicrobial therapy without wound débridement have had limited impact on decreasing biofilm infection, which remains a major problem in wound care. Current claims to manage wound biofilm infection rest on limited early-stage data. In most cases, such data originate from limited experimental systems that lack host immune defense. In making decisions on the choice of commercial products to manage wound biofilm infection, it is important to critically appreciate the mechanism of action and significance of the relevant experimental system. In this work, the authors critically review different categories of antibiofilm products, with emphasis on their strengths and limitations as evident from the published literature.

Evaluation of effectiveness of a new treatment method for healing infected wounds: an animal model

OBJECTIVE

To evaluate the effectiveness of a new treatment method in healing superficial infected wounds compared with surgical debridement with chlorhexidine solution.

METHOD

In this animal model, two wounds were created on the back of 10 male adult rabbits. Wounds treated by Method 1 were debrided using 0.02% chlorhexidine aqueous solution and an antibiotic topical ointment. Wounds treated by Method 2 wounds were treated using a newly developed device which enabled visual monitoring of the wound as it was treated with various pharmacological solutions (including antiseptic, antiseptic oxidant and an osmotically active agent) specifically formulated for each wound healing stage. Wound area size (using digital planimetry) and time taken to clean the wound were recorded, and biopsies were taken, at the beginning of the study and at various timepoints throughout.

RESULT

It was observed that both wound cleaning and wound healing were accelerated by treatment with method 2 compared with method 1 (by 43.8% and 36.7%, respectively). There were also a significantly smaller number of complications in these wounds [p=0.0044] due to the positive ratios of neutrophils and fibroblasts in the wound cavities (from the third to the fourteenth day after wound modelling).

CONCLUSION

Wounds treated with the new device in method 2 had a shorter wound healing time than wounds treated with a traditional method. The automated influx-outflow of solutions removed any fragments of necrotic tissue from the wound surface. Wounds were able to be monitored without the need to remove dressings. The transparent, airtight film, which allowed for wound monitoring without the need to remove dressings, meant that suturing was not required. This resulted in no complications in the wounds treated by this new method.

A Pilot Study of Negative Pressure Therapy with Autologous Skin Cell Suspensions in a Porcine Model

BACKGROUND

Negative pressure wound therapy (NPWT) is an option for securing meshed split thickness skin grafts (mSTSGs) after burn excision to optimize skin graft adherence. Recently, the use of autologous skin cell suspension (ASCS) has been approved for use in the treatment of burn injuries in conjunction with mSTSGs.To date, limited data exists regarding the impact of NPWT on healing outcomes when the cellular suspension is utilized. It was hypothesized that NPWT would not negatively impact wound healing of ASCS+mSTSG.

MATERIALS AND METHODS

A burn, excision, mSTSG, ASCS ± NPWT model was used. Two Duroc pigs were utilized in this experiment, each with 2 sets of paired burns. Four wounds received mSTSG+ASCS+NPWT through post-operative day 3, and 4 wounds received mSTSG+ACSC+ traditional ASCS dressings. Cellular viability was characterized prior to spraying. Percent re-epithelialization, graft-adherence, pigmentation, elasticity, and blood perfusion and blood vessel density were assessed at multiple time points through 2 weeks.

RESULTS

All wounds healed within 14 days with minimal scar pathology and no significant differences in percent re-epithelialization between NPWT, and non-NPWT wounds were observed. Additionally, no differences were detected for pigmentation, perfusion, or blood vessel density. NPWT treated wounds had less graft loss and improved elasticity, with elasticity being statistically different.

CONCLUSIONS

These data suggest the positive attributes of the cellular suspension delivered are retained following the application of negative pressure. Re-epithelialization, revascularization, and repigmentation are not adversely impacted. The use of NPWT may be considered as an option when using ASCS with mSTSGs for the treatment of full-thickness burns.

Evaluation of Pseudomonas aeruginosa pathogenesis and therapeutics in military-relevant animal infection models

Modern combat-related injuries are often associated with acute polytrauma. As a consequence of severe combat-related injuries, a dysregulated immune response results in serious infectious complications. The gram-negative bacterium Pseudomonas aeruginosa is an opportunistic pathogen that often causes life-threatening bloodstream, lung, bone, urinary tract, and wound infections following combat-related injuries. The rise in the number of multidrug-resistant P. aeruginosa strains has elevated its importance to civilian clinicians and military medicine. Development of novel therapeutics and treatment options for P. aeruginosa infections is urgently needed. During the process of drug discovery and therapeutic testing, in vivo testing in animal models is a critical step in the bench-to-bedside approach, and required for Food and Drug Administration approval. Here, we review current and past literature with a focus on combat injury-relevant animal models often used to understand infection development, the interplay between P. aeruginosa and the host, and evaluation of novel treatments. Specifically, this review focuses on the following animal infection models: wound, burn, bone, lung, urinary tract, foreign body, and sepsis.

Strong Antimicrobial and Healing Effects of Beta-Acids from Hops in Methicillin-Resistant Staphylococcus aureus-Infected External Wounds In Vivo

Staphylococcus (S.) aureus is an important causative agent of wound infections with increasing incidence in the past decades. Specifically, the emergence of methicillin-resistant S. aureus (MRSA) causes serious problems, especially in nosocomial infections. Therefore, there is an urgent need to develop of alternative or supportive antimicrobial therapeutic modalities to meet these challenges. Purified compounds from hops have previously shown promising antimicrobial effects against MRSA isolates in vitro. In this study, purified beta-acids from hops were tested for their potential antimicrobial and healing properties using a porcine model of wounds infected by MRSA. The results show highly significant antimicrobial effects of the active substance in both the powder and Ambiderman-based application forms compared to both no-treatment control and treatment with Framycoin. Moreover, the macroscopic evaluation of the wounds during the treatment using the standardized Wound Healing Continuum indicated positive effects of the beta-acids on the overall wound healing. This is further supported by the microscopic data, which showed a clear improvement of the inflammatory parameters in the wounds treated by beta-acids. Thus, using the porcine model, we demonstrate significant therapeutic effects of hops compounds in the management of wounds infected by MRSA. Beta-acids from hops, therefore, represent a suitable candidate for the treatment of non-responsive nosocomial tissue infections by MRSA.

Antibiofilm and antivirulence potential of silver nanoparticles against multidrug-resistant Acinetobacter baumannii

We aimed to isolate Acinetobacter baumannii (A. baumannii) from wound infections, determine their resistance and virulence profile, and assess the impact of Silver nanoparticles (AgNPs) on the bacterial growth, virulence and biofilm-related gene expression. AgNPs were synthesized and characterized using TEM, XRD and FTIR spectroscopy. A. baumannii (n = 200) were isolated and identified. Resistance pattern was determined and virulence genes (afa/draBC, cnf1, cnf2, csgA, cvaC, fimH, fyuA, ibeA, iutA, kpsMT II, PAI, papC, PapG II, III, sfa/focDE and traT) were screened using PCR. Biofilm formation was evaluated using Microtiter plate method. Then, the antimicrobial activity of AgNPs was evaluated by the well-diffusion method, growth kinetics and MIC determination. Inhibition of biofilm formation and the ability to disperse biofilms in exposure to AgNPs were evaluated. The effect of AgNPs on the expression of virulence and biofilm-related genes (bap, OmpA, abaI, csuA/B, A1S_2091, A1S_1510, A1S_0690, A1S_0114) were estimated using QRT-PCR. In vitro infection model for analyzing the antibacterial activity of AgNPs was done using a co-culture infection model of A. baumannii with human fibroblast skin cell line HFF-1 or Vero cell lines. A. baumannii had high level of resistance to antibiotics. Most of the isolates harbored the fimH, afa/draBC, cnf1, csgA and cnf2, and the majority of A. baumannii produced strong biofilms. AgNPs inhibited the growth of A. baumannii efficiently with MIC ranging from 4 to 25 µg/ml. A. baumannii showed a reduced growth rate in the presence of AgNPs. The inhibitory activity and the anti-biofilm activity of AgNPs were more pronounced against the weak biofilm producers. Moreover, AgNPs decreased the expression of kpsMII , afa/draBC,bap, OmpA, and csuA/B genes. The in vitro infection model revealed a significant antibacterial activity of AgNPs against extracellular and intracellular A. baumannii. AgNPs highly interrupted bacterial multiplication and biofilm formation. AgNPs downregulated the transcription level of important virulence and biofilm-related genes. Our findings provide an additional step towards understanding the mechanisms by which sliver nanoparticles interfere with the microbial spread and persistence.

The sorptivity and durability of gelling fibre dressings tested in a simulated sacral pressure ulcer system

Wound‐dressing performances are affected by exudate viscosity, resistance to flow because of gravity, and bodyweight loads, the level of which is related to the body position. Here, we focussed on two dressing properties: (a) Sorptivity—the ability of dressings to transfer exudate away from the wound bed by capillary action—and (b) Durability—the capacity of dressings to maintain their integrity over time and during their removal. Both properties are critically important for avoiding further tissue damage but require the development of new laboratory tests for their measurement. A computer‐controlled phantom of an exuding sacral pressure ulcer has therefore been developed and used to compare the performances of Exufiber (Mölnlycke Health Care) vs an alternative market‐leading dressing. Sorptivity was determined using weight tests, and durability was measured through tensile tests of the used dressings. For a supine configuration, the Exufiber dressing demonstrated ~three times higher sorptivity and better durability, withstanding ~five times greater strain energy than the other product before failure occurred. This work paves the way for quantitative, standardised testing of dressings in all aspects of exudate management. The reported tests are further suitable for testing dressing combinations or how dressings interact with negative pressure wound therapy.

Coming to Consensus: What Defines Deep Partial Thickness Burn Injuries in Porcine Models?

Deep partial thickness burns are clinically prevalent and difficult to diagnose. In order to develop methods to assess burn depth and therapies to treat deep partial thickness burns, reliable, accurate animal models are needed. The variety of animal models in the literature and the lack of precise details reported for the experimental procedures make comparison of research between investigators challenging and ultimately affect translation to patients. They sought to compare deep partial thickness porcine burn models from five well-established laboratories. In doing so, they uncovered a lack of consistency in approaches to the evaluation of burn injury depth that was present within and among various models. They then used an iterative process to develop a scoring rubric with an educational component to facilitate burn injury depth evaluation that improved reliability of the scoring. Using the developed rubric to re-score the five burn models, they found that all models created a deep partial thickness injury and that agreement about specific characteristics identified on histological staining was improved. Finally, they present consensus statements on the evaluation and interpretation of the microanatomy of deep partial thickness burns in pigs.

A Textile Pile Debridement Material Consisting of Polyester Fibers for in Vitro Removal of Biofilm

Biofilms formed on skin wound lead to inflammation and a delay of healing. In the present work, a novel textile pile debridement material was prepared and treated by plasma. Samples before and after plasma treatment were characterized by a series of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and water uptake capacity. Besides, mechanical, coagulation, and in vitro biofilm removal performances of the textile pile debridement material were evaluated, with a medical gauze as a control. The results demonstrate that the plasma treatment produced corrosions and oxygen-containing polar groups on the fiber surface, offering an enhanced water uptake capacity of the textile pile debridement material. In addition, compressive tests certify the mechanical performances of the textile pile debridement material in both dry and wet conditions. The results from a kinetic clotting time test suggest a favorable ability to promote blood coagulation. Furthermore, the results of an MTT cell viability assay, SEM, and confocal laser scanning microscopy (CLSM) illustrate that the textile pile debridement material demonstrates a more superior in vitro biofilm removal performance than medical gauze. All of these characterizations suggest that the textile pile debridement material can offer a feasible application for clinical wound debridement.

Clinical impact of an anti-biofilm Hydrofiber dressing in hard-to-heal wounds previously managed with traditional antimicrobial products and systemic antibiotics

Background

Hard-to-heal wounds are often compromised by the presence of biofilm. This presents an infection risk, yet traditional antimicrobial wound care products and systemic antibiotics are often used despite the uncertainty of therapeutic success and wound progression. The aim of this study was to investigate the clinical impact of a next-generation anti-biofilm Hydrofiber wound dressing (AQUACEL Ag+ Extra[AQAg+ E]) in hard-to-heal wounds that had previously been treated unsuccessfully with traditional silver-, iodine- or polyhexamethylene biguanide (PHMB)-containing dressings and products and/or systemic antibiotics.

Methods

Clinical case study evaluations of the anti-biofilm dressing were conducted, where deteriorating or stagnant wounds were selected by clinicians and primary dressings were replaced by the anti-biofilm dressing for up to 4 weeks, or as deemed clinically appropriate, with monitoring via case report forms. The data was stratified for cases where traditional silver-, iodine- or PHMB-containing products, or systemic antibiotics, had been used prior to the introduction of the anti-biofilm dressing.

Results

Sixty-five cases were identified for inclusion, wounds ranging in duration from 1 week to 20 years (median: 12 months). In 47 (72%) cases the wounds were stagnant, while 15 (23%) were deteriorating; 3 wounds were not recorded. After an average of 4.2 weeks of management with the anti-biofilm dressing (range: 1-11 weeks), in 11 (17%) cases the wounds had healed (i.e. complete wound closure), 40 (62%) wounds improved, 9 (14%) wounds remained the same and 5 (8%) wounds deteriorated.

Conclusions

The introduction of this anti-biofilm dressing into protocols of care that had previously involved wound management with traditional antimicrobial products and/or antibiotics was shown to facilitate improvements in the healing status of most of these hard-to-heal wounds. Dressings containing proven anti-biofilm technology, in combination with antimicrobial silver and exudate management technology, appear to be an effective alternative to traditional antimicrobial products and antibiotics in the cases presented here. The use of antimicrobial wound dressings that contain anti-biofilm technology may have a key role to play in more effective wound management and antibiotic stewardship.

Use of internally validated in vitro biofilm models to assess antibiofilm performance of silver-containing gelling fibre dressings

Objective:

To assess the efficacy of five silver-containing gelling fibre wound dressings against single-species and multispecies biofilms using internally validated, UKAS-accredited in vitro test models.

Method:

Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans single- and multispecies biofilms were cultured using Centres for Disease Control (CDC) biofilm reactors and colony drip flow reactors (CDFR). Following a 72 hour incubation period, the substrates on which biofilms were grown were rinsed to remove planktonic microorganisms and then challenged with fully hydrated silver-containing gelling fibre wound dressings. Following dressing application for 24 or 72 hours, remaining viable organisms from the treated biofilms were quantified.

Results:

In single-species in vitro models, all five antimicrobial dressings were effective in eradicating Staphylococcus aureus and Pseudomonas aeruginosa biofilm bacteria. However, only one of the five dressings (Hydrofiber technology with combination antibiofilm/antimicrobial technology) was able to eradicate the more tolerant single-species Candida albicans biofilm. In a more complex and stringent CDFR biofilm model, the hydrofiber dressing with combined antibiofilm/antimicrobial technology was the only dressing that was able to eradicate multispecies biofilms such that no viable organisms were recovered.

Conclusion:

Given the detrimental effects of biofilm on wound healing, stringent in vitro biofilm models are increasingly required to investigate the efficacy of antimicrobial dressings. Using accredited in vitro biofilm models of increasing complexity, differentiation in the performance of dressings with combined antibiofilm/antimicrobial technology against those with antimicrobial properties alone, was demonstrated.

Antibiotic Delivery Strategies to Treat Skin Infections When Innate Antimicrobial Defense Fails

The epidermal skin barrier protects the body from a host of daily challenges, providing protection against mechanical insults and the absorption of chemicals and xenobiotics. In addition to the physical barrier, the epidermis also presents an innate defense against microbial overgrowth. This is achieved through the presence of a diverse collection of microorganisms on the skin (the "microbiota") that maintain a delicate balance with the host and play a significant role in overall human health. When the skin is wounded, the local tissue with a compromised barrier can become colonized and ultimately infected if bacterial growth overcomes the host response. Wound infections present an immense burden in healthcare costs and decreased quality of life for patients, and treatment becomes increasingly important because of the negative impact that infection has on slowing the rate of wound healing. In this review, we discuss specific challenges of treating wound infections and the advances in drug delivery platforms and formulations that are under development to improve topical delivery of antimicrobial treatments.

Clinical and Antimicrobial Efficacy of a Silver Foam Dressing With Silicone Adhesive in Diabetic Foot Ulcers With Mild Infection

The use of an antimicrobial dressing instead of a non-antimicrobial dressing may increase the number of diabetic foot ulcers healed over a medium-term follow-up period. The study aim was to evaluate the clinical and microbiological efficacy of a silver foam dressing in the management of diabetic foot ulcers. We conducted a single-center, prospective, open, noncontrolled study involving 21 outpatients with diabetic foot ulcers with mild infection. All patients received standard of care for their wounds and a silver foam dressing with silicone adhesive was applied twice per week for wound management during a 6-week treatment period. Soft tissue punch biopsies were taken every second week for qualitative and quantitative microbiological analysis. Wounds were assessed at patient admission, and wound bed tissue was evaluated for presence, quality, and consistency of granulation tissue. Clinical evaluation revealed improvements in wound conditions as a result of treatment with the silver dressing. Wollina wound scores improved significantly, from a mean score of 3.9 ± 1.6 points at inclusion to 6.1 ± 1.3 points at the end of the study (n = 19, P < .001). Treatment with the silver dressing resulted in significant decreases in the bioburden of classically considered diabetic foot ulcer pathogenic organisms such as Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus, Enterobacteriaceae species, Pseudomonas aeruginosa, and other nonfermenting gram-negative bacilli. Findings revealed that the use of silver foam dressing significantly reduced the pathogenic bacterial load and markedly improved the clinical outcome in patients with diabetic foot ulcer with mild infection over a 6-week treatment period.