Effective Method to Remove Wound Bacteria: Comparison of Various Debridement Modalities in an In Vivo Porcine Model

Coblation Versus Surgical Debridement Against MRSA Infection in Wounds With Shrapnel: A Preliminary Study

INTRODUCTION

Debridement plays a critical role in wound management. In addition to removing necrotic tissue, debridement can eliminate bacteria frequently harbored within the tissue. This study evaluated a novel debridement method that uses plasma-based radiofrequency technology to remove tissue and bacteria. Coblation is a technology that uses radiofrequency energy to excite the electrolytes in a conductive medium, such as saline, to create a precisely focused plasma. This plasma field contains highly energized particles that possess sufficient energy to break tissue molecular bonds, causing the tissue to dissolve at relatively low temperatures (typically 40 °C to 70 °C).

MATERIALS AND METHODS

Eighteen deep dermal wounds measuring 22 mm × 22 mm × 3 mm deep were created on pigs. Wounds were inoculated with methicillin-resistant Staphylococcus aureus USA300 (MRSA USA300) in combination with shrapnel and then covered with a polyurethane dressing for 24 hours. Wounds were then randomly assigned to one of the 3 treatment groups: (1) Coblation, (2) surgical debridement, and (3) no debridement. Wounds were biopsied on days 0, 5, 9, and 12, and specimens were processed for MRSA counts using selective media. Statistical analysis was performed using IBM SPSS statistics 27 using one-way ANOVA.

RESULTS

Comparison between coblation and surgical debridement showed a decrease in bacterial count in all assessment times. The lowest bacterial count in all assessment times was observed in wounds debrided with coblation showing a statistically significant (P ≤ .05) decrease in more than 2 Log CFU/g on days 0, 5, and 9 compared to no debridement. On day 12, coblation-debrided wounds exhibited 6.10 ± 0.22 Log CFU/g, and this value represents 99.99% of reduction compared with non-debrided wounds (P ≤ .05). More than 96% of reduction (P ≤ .05) resulted in wounds treated with coblation compared with surgically debrided.

CONCLUSIONS

Reducing MRSA bacterial infection counts, especially of biofilm-associated organisms, in combination with shrapnel may have important clinical implications, especially for the military personnel. Further research into the use of this technology in wound management is warranted.

Efficacy of EDTA-NS irrigation in eradicating Staphylococcus aureus biofilm-associated infection

Aims

To investigate the efficacy of ethylenediaminetetraacetic acid-normal saline (EDTA-NS) in dispersing biofilms and reducing bacterial infections.

Methods

EDTA-NS solutions were irrigated at different durations (1, 5, 10, and 30 minutes) and concentrations (1, 2, 5, 10, and 50 mM) to disrupt Staphylococcus aureus biofilms on Matrigel-coated glass and two materials widely used in orthopaedic implants (Ti-6Al-4V and highly cross-linked polyethylene (HXLPE)). To assess the efficacy of biofilm dispersion, crystal violet staining biofilm assay and colony counting after sonification and culturing were performed. The results were further confirmed and visualized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). We then investigated the efficacies of EDTA-NS irrigation in vivo in rat and pig models of biofilm-associated infection.

Results

When 10 mM or higher EDTA-NS concentrations were used for ten minutes, over 99% of S. aureus biofilm formed on all three types of materials was eradicated in terms of absorbance measured at 595 nm and colony-forming units (CFUs) after culturing. Consistently, SEM and CSLM scanning demonstrated that less adherence of S. aureus could be observed on all three types of materials after 10 mM EDTA-NS irrigation for ten minutes. In the rat model, compared with NS irrigation combined with rifampin (Ti-6Al-4V wire-implanted rats: 60% bacteria survived; HXLPE particle-implanted rats: 63.3% bacteria survived), EDTA-NS irrigation combined with rifampin produced the highest removal rate (Ti-6Al-4V wire-implanted rats: 3.33% bacteria survived; HXLPE particle-implanted rats: 6.67% bacteria survived). In the pig model, compared with NS irrigation combined with rifampin (Ti-6Al-4V plates: 75% bacteria survived; HXLPE bearings: 87.5% bacteria survived), we observed a similar level of biofilm disruption on Ti-6Al-4V plates (25% bacteria survived) and HXLPE bearings (37.5% bacteria survived) after EDTA-NS irrigation combined with rifampin. The in vivo study revealed that the biomass of S. aureus biofilm was significantly reduced when treated with rifampin following irrigation and debridement, as indicated by both the biofilm bacterial burden and crystal violet staining. EDTA-NS irrigation (10 mM/10 min) combined with rifampin effectively removes S. aureus biofilm-associated infections both in vitro and in vivo.

Conclusion

EDTA-NS irrigation with or without antibiotics is effective in eradicating S. aureus biofilm-associated infection both ex and in vivo.

Preliminary evidence supporting a new enzymatic debridement product for use in chronic wounds

A new recombinant proteolytic enzyme, isolated from maggot saliva, with fibrinolytic action has been investigated through a series of non-clinical toxicology and in-vitro/in-vivo pharmacology studies to explore its potential safety and efficacy as an enzymatic debridement agent for use in chronic wounds. Studies indicate that the enzyme has a good safety profile. When locally administered, it is not detrimental to wound healing, is non-sensitising and is rapidly inactivated in the systemic circulation. Adverse effects are limited, at very high concentrations, to transient erythema at the site of application. In-vitro testing indicates that the enzyme, whilst selective for fibrin, has additional proteolytic action against collagen and elastin, with enzymatic action for all three substrates being dose dependent. In-vivo, we used an established MRSA biofilm model, in which microbiological counts were used as a surrogate for debridement efficacy. Here, we showed that higher concentrations of the enzyme in a formulated proprietary gel, significantly reduced MRSA counts over a period of 2 to 14 days, and significantly improved the vascularity of the wound at 14 days. Together, these data support the potential for this maggot-derived proteolytic enzyme as a clinically effective debriding agent.

Murine burn lesion model for studying acute and chronic wound infections

Acute wounds, such as thermal injury, and chronic wounds are challenging for patients and the healthcare system around the world. Thermal injury of considerable size induces immunosuppression, which renders the patient susceptible to wound infections, but also in other foci like the airways and urinary tract. Infected thermal lesions can progress to chronic wounds with biofilm making them more difficult to treat. While animal models have their limitations, murine wound models are still the best tool at the moment to identify strategies to overcome these challenges. Here, we present a murine burn model, which has been developed to study biofilm formation, the significance of wound healing, and for identifying novel treatment candidates. Investigating the effect of a thermal injury in mice, we observed that 48 h after introduction of the injury, the mice showed a reduction in polymorphonuclear neutrophil granulocytes (PMNs) and a reduced capacity for phagocytosis and oxidative burst. Regarding the chronic wound, Pseudomonas aeruginosa biofilm arrested wound healing and kept the wound in an inflammatory state, but suppressing PMN function by means of the PMN factor S100A8/A9, corresponding to observations in human venous leg ulcers. Monotherapy and dual treatment with S100A8/A9 and ciprofloxacin on P. aeruginosa biofilm-infected murine wounds have been investigated. In combination, S100A8/A9 and ciprofloxacin reduced the bacterial quantity, lowered the proinflammatory response, and increased anti-inflammatory cytokines after 4 days of treatment. When the treatment was prolonged, an additional prevention of resistance development was detected in all the dual-treated mice. In the present review, we provide data on using the murine model for research with the aim of better understanding pathophysiology of wounds and for identifying novel treatments for humans suffering from these lesions.

Nanomaterials-based drug delivery approaches for wound healing

Abstract:

Wound healing is a complex and dynamic process that requires intricate synchronization between multiple cell types within appropriate extracellular microenvironment. Wound healing process involves four overlapping phases in a precisely regulated manner, consisting of hemostasis, inflammation, proliferation, and maturation. For an effective wound healing all four phases must follow in a sequential pattern within a time frame. Several factors might interfere with one or more of these phases in healing process, thus causing improper or impaired wound healing resulting in non-healing chronic wounds. The complications associated with chronic non-healing wounds, along with the limitations of existing wound therapies, have led to the development and emergence of novel and innovative therapeutic interventions. Nanotechnology presents unique and alternative approaches to accelerate the healing of chronic wounds by the interaction of nanomaterials during different phases of wound healing. This review focuses on recent innovative nanotechnology-based strategies for wound healing and tissue regeneration based on nanomaterials, including nanoparticles, nanocomposites and scaffolds. The efficacy of the intrinsic therapeutic potential of nanomaterials (including silver, gold, zinc oxide, copper, cerium oxide, etc.) and the ability of nanomaterials as carriers (liposomes, hydrogels, polymeric nanomaterials, nanofibers) as therapeutic agents associated with wound-healing applications have also been addressed. The significance of these nanomaterial-based therapeutic interventions for wound healing needs to be highlighted to engage researchers and clinicians towards this new and exciting area of bio-nanoscience. We believe that these recent developments will offer researchers an updated source on the use of nanomaterials as an advanced approach to improve wound healing.

Novel Diagnostic Technologies and Therapeutic Approaches Targeting Chronic Wound Biofilms and Microbiota

Purpose of Review

To provide an up-to-date overview of recent developments in diagnostic methods and therapeutic approaches for chronic wound biofilms and pathogenic microbiota.

Recent Findings

Biofilm infections are one of the major contributors to impaired wound healing in chronic wounds, including diabetic foot ulcers, venous leg ulcers, pressure ulcers, and nonhealing surgical wounds. As an organized microenvironment commonly including multiple microbial species, biofilms develop and persist through methods that allow evasion from host immune response and antimicrobial treatments. Suppression and reduction of biofilm infection have been demonstrated to improve wound healing outcomes. However, chronic wound biofilms are a challenge to treat due to limited methods for accurate, accessible clinical identification and the biofilm's protective properties against therapeutic agents. Here we review recent approaches towards visual markers for less invasive, enhanced biofilm detection in the clinical setting. We outline progress in wound care treatments including investigation of their antibiofilm effects, such as with hydrosurgical and ultrasound debridement, negative pressure wound therapy with instillation, antimicrobial peptides, nanoparticles and nanocarriers, electroceutical dressings, and phage therapy.

Summary

Current evidence for biofilm-targeted treatments has been primarily conducted in preclinical studies, with limited clinical investigation for many therapies. Improved identification, monitoring, and treatment of biofilms require expansion of point-of-care visualization methods and increased evaluation of antibiofilm therapies in robust clinical trials.

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.

Phytochemical-Based Nano-Pharmacotherapeutics for Management of Burn Wound Healing

Medicinal plants have been used since ancient times for their various therapeutic activities and are safer compared to modern medicines, especially when properly identifying and preparing them and choosing an adequate dose administration. The phytochemical compounds present in plants are progressively yielding evidence in modern drug delivery systems by treating various diseases like cancers, coronary heart disease, diabetes, high blood pressure, inflammation, microbial, viral and parasitic infections, psychotic diseases, spasmodic conditions, ulcers, etc. The phytochemical requires a rational approach to deliver the compounds to enhance the efficacy and to improve patients’ compatibility. Nanotechnology is emerging as one of the most promising strategies in disease control. Nano-formulations could target certain parts of the body and control drug release. Different studies report that phytochemical-loaded nano-formulations have been tested successfully both in vitro and in vivo for healing of skin wounds. The use of nano systems as drug carriers may reduce the toxicity and enhance the bioavailability of the incorporated drug. In this review, we focus on various nano-phytomedicines that have been used in treating skin burn wounds, and how both nanotechnology and phytochemicals are effective for treating skin burns.

Novel Cyclic Lipopeptides Fusaricidin Analogs for Treating Wound Infections

Both acute and chronic cutaneous wounds are often difficult to treat due to the high-risk for bacterial contamination. Once hospitalized, open wounds are at a high-risk for developing hospital-associated infections caused by multi drug-resistant bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa. Treating these infections is challenging, not only because of antibiotic resistance, but also due to the production of biofilms. New treatment strategies are needed that will help in both stimulating the wound healing process, as well as preventing and eliminating bacterial wound infections. Fusaricidins are naturally occurring cyclic lipopeptides with antimicrobial properties that have shown to be effective against a variety of fungi and Gram-positive bacteria, with low toxicity. Continuing with our efforts toward the identification of novel cyclic lipopeptides Fusaricidin analogs, herein we report the synthesis and evaluation of the antimicrobial activity for two novel cyclic lipopeptides (CLP), CLP 2605-4 and CLP 2612-8.1 against methicillin resistant S. aureus and P. aeruginosa, respectively, in in vivo porcine full thickness wound model. Both CLPs were able to reduce bacterial counts by approximately 3 log CFU/g by the last assessment day. Peptide 2612-8.1 slightly enhanced the wound healing, however, wounds treated with peptide 2605-4, have shown higher levels of inflammation and impaired wound healing process. This study highlights the importance of identifying new antimicrobials that can combat bacterial infection while not impeding tissue repair.

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.

Antimicrobial laser-activated sealants for combating surgical site infections

Surgical-site infections (SSIs) occur in 2-5% of patients undergoing surgery in the US alone, impacting 300 000-500 000 lives each year, and presenting up to 11 times greater risk of death compared to patients without SSIs. The most common cause of SSI is Staphylococcus aureus, and methicillin-resistant S. aureus (MRSA) is the most common pathogen in community hospitals. Current clinical devices used for approximating incisions and traumatic lacerations include sutures, adhesives, tapes, or staples with or without antimicrobial incorporation. However, current closure technologies may not provide adequate protection against infection, are susceptible to wound dehiscence, and can result in delayed biomechanical recoveries. Laser-activated tissue repair is a sutureless technique in which chromophore-loaded sealants convert laser light energy to heat in order to induce rapid tissue sealing. Here, we describe the generation and evaluation of laser-activated sealant (LASE) biomaterials, in which, indocyanine green (ICG), an FDA-approved dye, was embedded in a silk fibroin matrix and cast into films as wound sealants. Silk-ICG films were subjected to different near-infrared (NIR) laser powers to identify temperatures optimal for laser sealing of soft tissues. A mathematical model was developed in order to determine the photothermal conversion efficiency of LASEs following laser irradiation. NIR laser activation of silk-ICG LASEs increased the recovery of skin biomechanical strength compared to sutured skin in full-thickness incisional wounds in immunocompetent mice, and live animal imaging indicated persistence of silk-ICG LASEs over several days. LASEs loaded with the antibiotic vancomycin demonstrated higher efficacies for combating MRSA infections in a mouse model of surgical site infection compared to antibacterial sutures. Our results demonstrate that LASEs can be loaded with antimicrobial drugs and may serve as new multifunctional biomaterials for rapid tissue sealing, repair and surgical site protection following surgery.

In vivo analysis of a first-in-class tri-alkyl norspermidine-biaryl antibiotic in an active release coating to reduce the risk of implant-related infection

Prosthetic joint infection (PJI) is a well-known and persisting problem. Active release coatings have promise to provide early protection to an implant by eradicating small colony biofilm contaminants or planktonic bacteria that can form biofilm. Traditional antibiotics can be limited as active release agents in that they have limited effect against biofilms and develop resistance at sub-lethal concentrations. A unique first-in-class compound (CZ-01127) was assessed as the active release agent in a silicone (Si)-based coating to prevent PJI in a sheep model of joint space infection. Titanium (Ti) plugs contained a porous coated Ti (PCTi) region and polymer-coated region. Plugs were implanted into a femoral condyle of sheep to assess the effect of the Si polymer on cancellous bone ingrowth, the effect of CZ-01127 on bone ingrowth, and the ability of CZ-01127 to prevent PJI. Microbiological results showed that CZ-01127 was able to eradicate bacteria in the local region of the implanted plugs. Data further showed that Si did not adversely affect bone ingrowth. However, bacteria that reached the joint space (synovium) were not fully eradicated. Outcomes suggested that the CZ-01127 coating provided local protection to the implant system in a challenging model, the design of which could be beneficial for testing future antimicrobial therapies for PJI. STATEMENT OF SIGNIFICANCE: Periprosthetic joint infection (PJI) is now commonplace, and constitutes an underlying problem that patients and physicians face. Active release antibiotic coatings have potential to prevent these infections. Traditional antibiotics are limited in their ability to eradicate bacteria that reside in biofilms, and are more susceptible to resistance development. This study addressed these limitations by testing the efficacy of a unique antimicrobial compound in a coating that was tested in a challenging sheep model of PJI. The unique coating was able to eradicate bacteria and prevent infection in the environment adjacent to the implant. Bacteria that escaped into the joint space still caused infection, yet benchmark data can be used to optimize the coating and translate it toward clinical use.

Nano-drug delivery systems in wound treatment and skin regeneration

Skin damages are defined as one of most common lesions people suffer from, some of wounds are notoriously difficult to eradicate such as chronic wounds and deep burns. Existing wound therapies have been proved to be inadequate and far from satisfactory. The cutting-edge nanotechnology offers an unprecedented opportunity to revolutionize and invent new therapies or boost the effectiveness of current medical treatments. In particular, the nano-drug delivery systems anchor bioactive molecules to applied area, sustain the drug release and explicitly enhance the therapeutic efficacies of drugs, thus making a fine figure in field relevant to skin regeneration. This review summarized and discussed the current nano-drug delivery systems holding pivotal potential for wound healing and skin regeneration, with a special emphasis on liposomes, polymeric nanoparticles, inorganic nanoparticles, lipid nanoparticles, nanofibrous structures and nanohydrogel.

[Research progress of chronic wound debridement]

Objective

To review the research progress of chronic wound debridement.

Methods

The recent related literature concerning the mechanisms, advantages, limitations, and indications of the technologies of chronic wound debridement was extensively consulted, reviewed, and summarized.

Results

Debridement is essential for chronic wound healing, which includes autolytic debridement, enzymatic debridement, biodebridement, mechanical debridement, sharp/surgical debridement, ultrasound debridement, hydrosurgery debridement, and coblation debridement. Each technique has its own advantages and disadvantages.

Conclusion

There are many types of technologies of chronic wound debridement, which can be chosen according to clinical conditions. It is showed there are more significant advantages associated with the technique of coblation debridement relatively, which also has greater potential. Further study is needed to improve its efficacy.

Guidelines for porcine models of human bacterial infections

During the last 10 years the number of porcine models for human bacterial infectious diseases has increased. In the future, this tendency is expected to continue and, therefore, the aim of the present review is to describe guidelines for the development and reporting of these models. The guidelines are based on a review of 122 publications of porcine models for different bacterial infectious diseases in humans. The review demonstrates a substantial lack of information in most papers which hampers reproducibility and continuation of the work that was established in the models. The guidelines describe overall principles related to the inoculum, the animal, the infected animal and the post-mortem characterization that are of crucial importance when porcine models of infectious diseases are developed, validated and reported.

Options and Limitations in Clinical Investigation of Bacterial Biofilms

Bacteria can form single- and multispecies biofilms exhibiting diverse features based upon the microbial composition of their community and microenvironment. The study of bacterial biofilm development has received great interest in the past 20 years and is motivated by the elegant complexity characteristic of these multicellular communities and their role in infectious diseases. Biofilms can thrive on virtually any surface and can be beneficial or detrimental based upon the community's interplay and the surface. Advances in the understanding of structural and functional variations and the roles that biofilms play in disease and host-pathogen interactions have been addressed through comprehensive literature searches. In this review article, a synopsis of the methodological landscape of biofilm analysis is provided, including an evaluation of the current trends in methodological research. We deem this worthwhile because a keyword-oriented bibliographical search reveals that less than 5% of the biofilm literature is devoted to methodology. In this report, we (i) summarize current methodologies for biofilm characterization, monitoring, and quantification; (ii) discuss advances in the discovery of effective imaging and sensing tools and modalities; (iii) provide an overview of tailored animal models that assess features of biofilm infections; and (iv) make recommendations defining the most appropriate methodological tools for clinical settings.

Development of a contaminated ischemic porcine wound model and the evaluation of bromelain based enzymatic debridement

OBJECTIVES

There are no well accepted animal models of chronic wounds, limiting advances in understanding and treatment of chronic ulcers. We developed a porcine wound model which combines multiple factors involved in chronic wounds to create a contaminated necrotic eschar and evaluated the debriding efficacy of a novel bromelain based enzymatic debriding agent (EscharEx).

METHODS

Contaminated ischemic wounds were created on the flanks of domestic pigs by 'sandwiching' the skin between 2 'O' rings (1 placed on the surface of the skin and the other underneath the skin) for 24h prior to dermatomal excision of the necrotic eschar and its contamination with Staphylococcus aureus and Candida albicans. After confirming the development of infected eschars, additional animals were used to compare the effects of daily application of topical EscharEx or its hydrating vehicle on eschar debridement as a control.

RESULTS

In all cases, application of the 'O' rings resulted in full thickness necrotic ecshars with invasive infections, which did not reepithelialize and sloughed off spontaneously within 14-21 days. All wounds reepithelialized within 28-42 days forming contracted scars. All EscharEx treated eschars were completely debrided within 7-9 days, while no debridement was evident in eschars treated with the control gel.

CONCLUSIONS

Our model simulates the initial phase of chronic wounds characterized by a contaminated necrotic eschar allowing evaluation of wound debriding agents, and that a bromelain-based debriding agent completely debrides the contaminated necrotic eschars within one week in this model.

Consensus guidelines for the identification and treatment of biofilms in chronic nonhealing wounds

BACKGROUND

Despite a growing consensus that biofilms contribute to a delay in the healing of chronic wounds, conflicting evidence pertaining to their identification and management can lead to uncertainty regarding treatment. This, in part, has been driven by reliance on in vitro data or animal models, which may not directly correlate to clinical evidence on the importance of biofilms. Limited data presented in human studies have further contributed to the uncertainty. Guidelines for care of chronic wounds with a focus on biofilms are needed to help aid the identification and management of biofilms, providing a clinical focus to support clinicians in improving patient care through evidence-based medicine.

METHODS

A Global Wound Biofilm Expert Panel, comprising 10 clinicians and researchers with expertise in laboratory and clinical aspects of biofilms, was identified and convened. A modified Delphi process, based on published scientific data and expert opinion, was used to develop consensus statements that could help identify and treat biofilms as part of the management of chronic nonhealing wounds. Using an electronic survey, panel members rated their agreement with statements about biofilm identification and treatment, and the management of chronic nonhealing wounds. Final consensus statements were agreed on in a face-to-face meeting.

RESULTS

Participants reached consensus on 61 statements in the following topic areas: understanding biofilms and the problems they cause clinicians; current diagnostic options; clinical indicators of biofilms; future options for diagnostic tests; treatment strategies; mechanical debridement; topical antiseptics; screening antibiofilm agents; and levels of evidence when choosing antibiofilm treatments.

CONCLUSION

This consensus document attempts to clarify misunderstandings about the role of biofilms in clinical practice, and provides a basis for clinicians to recognize biofilms in chronic nonhealing wounds and manage patients optimally. A new paradigm for wound care, based on a stepped-down treatment approach, was derived from the consensus statements.

Porcine Models of Biofilm Infections with Focus on Pathomorphology

Bacterial biofilm formation is one of the main reasons for a negative treatment outcome and a high recurrence rate for many chronic infections in humans. The optimal way to study both the biofilm forming bacteria and the host response simultaneously is by using discriminative, reliable, and reproducible animal models of the infections. In this review, the advantages of in vivo studies are compared to in vitro studies of biofilm formation in infectious diseases. The pig is the animal of choice when developing and applying large animal models of infectious diseases due to its similarity of anatomy, physiology, and immune system to humans. Furthermore, conventional pigs spontaneously develop many of the same chronic bacterial infections as seen in humans. Therefore, in this review porcine models of five different infectious diseases all associated with biofilm formation and chronicity in humans are described. The infectious diseases are: chronic wounds, endocarditis, pyelonephritis, hematogenous osteomyelitis, and implant-associated osteomyelitis (IAO).

Effectiveness of a polyhexanide irrigation solution on methicillin-resistant Staphylococcus aureus biofilms in a porcine wound model

Irrigation and removal of necrotic debris can be beneficial for proper healing. It is becoming increasingly evident that wounds colonized with biofilm forming bacteria, such as Staphylococcus aureus (SA), can be more difficult to eradicate. Here we report our findings of the effects of an irrigation solution containing propyl-betaine and polyhexanide (PHMB) on methicillin-resistant Staphylococcus aureus (MRSA) biofilms in a porcine wound model. Thirty-nine deep partial thickness wounds were created with six wounds assigned to one of six treatment groups: (i) PHMB, (ii) Ringer's solution, (iii) hypochlorous acid/sodium hypochlorite, (iv) sterile water, (v) octenidine dihydrochloride, and (vi) octenilin. Wounds were inoculated with MRSA and covered with a polyurethane dressing for 24 hours to allow biofilm formation. The dressings were then removed and the wounds were irrigated twice daily for 3 days with the appropriate solution. MRSA from four wounds were recovered from each treatment group at 3 days and 6 days hours after initial treatment. Irrigation of wounds with the PHMB solution resulted in 97·85% and 99·64% reductions of MRSA at the respective 3 days and 6 days assessment times when compared to the untreated group. Both of these reductions were statistically significant compared to all other treatment groups (P values <0·05).

Comparing the Effectiveness of Polymer Debriding Devices Using a Porcine Wound Biofilm Model

Objective: Debridement to remove necrotic and/or infected tissue and promote active healing remains a cornerstone of contemporary chronic wound management. While there has been a recent shift toward less invasive polymer-based debriding devices, their efficacy requires rigorous evaluation.

Approach: This study was designed to directly compare monofilament debriding devices to traditional gauze using a wounded porcine skin biofilm model with standardized application parameters. Biofilm removal was determined using a surface viability assay, bacterial counts, histological assessment, and scanning electron microscopy (SEM).

Results: Quantitative analysis revealed that monofilament debriding devices outperformed the standard gauze, resulting in up to 100-fold greater reduction in bacterial counts. Interestingly, histological and morphological analyses suggested that debridement not only removed bacteria, but also differentially disrupted the bacterially-derived extracellular polymeric substance. Finally, SEM of post-debridement monofilaments showed structural changes in attached bacteria, implying a negative impact on viability.

Innovation: This is the first study to combine controlled and defined debridement application with a biologically relevant ex vivo biofilm model to directly compare monofilament debriding devices.

Conclusion: These data support the use of monofilament debriding devices for the removal of established wound biofilms and suggest variable efficacy towards biofilms composed of different species of bacteria.

New Is Old, and Old Is New: Recent Advances in Antibiotic-Based, Antibiotic-Free and Ethnomedical Treatments against Methicillin-Resistant Staphylococcus aureus Wound Infections

Staphylococcus aureus is the most common pathogen of wound infections. Thus far, methicillin-resistant S. aureus (MRSA) has become the major causative agent in wound infections, especially for nosocomial infections. MRSA infections are seldom eradicated by routine antimicrobial therapies. More concerning, some strains have become resistant to the newest antibiotics of last resort. Furthermore, horizontal transfer of a polymyxin resistance gene, mcr-1, has been identified in Enterobacteriaceae, by which resistance to the last group of antibiotics will likely spread rapidly. The worst-case scenario, "a return to the pre-antibiotic era", is likely in sight. A perpetual goal for antibiotic research is the discovery of an antibiotic that lacks resistance potential, such as the recent discovery of teixobactin. However, when considering the issue from an ecological and evolutionary standpoint, it is evident that it is insufficient to solve the antibiotic dilemma through the use of antibiotics themselves. In this review, we summarized recent advances in antibiotic-based, antibiotic-free and ethnomedical treatments against MRSA wound infections to identify new clues to solve the antibiotic dilemma. One potential solution is to use ethnomedical drugs topically. Some ethnomedical drugs have been demonstrated to be effective antimicrobials against MRSA. A decline in antibiotic resistance can therefore be expected, as has been demonstrated when antibiotic-free treatments were used to limit the use of antibiotics. It is also anticipated that these drugs will have low resistance potential, although there is only minimal evidence to support this claim to date. More clinical trials and animal tests should be conducted on this topic.

Inhibition of Pseudomonas aeruginosa biofilm formation on wound dressings

Chronic nonhealing skin wounds often contain bacterial biofilms that prevent normal wound healing and closure and present challenges to the use of conventional wound dressings. We investigated inhibition of Pseudomonas aeruginosa biofilm formation, a common pathogen of chronic skin wounds, on a commercially available biological wound dressing. Building on prior reports, we examined whether the amino acid tryptophan would inhibit P. aeruginosa biofilm formation on the three-dimensional surface of the biological dressing. Bacterial biomass and biofilm polysaccharides were quantified using crystal violet staining or an enzyme linked lectin, respectively. Bacterial cells and biofilm matrix adherent to the wound dressing were visualized through scanning electron microscopy. D-/L-tryptophan inhibited P. aeruginosa biofilm formation on the wound dressing in a dose dependent manner and was not directly cytotoxic to immortalized human keratinocytes although there was some reduction in cellular metabolism or enzymatic activity. More importantly, D-/L-tryptophan did not impair wound healing in a splinted skin wound murine model. Furthermore, wound closure was improved when D-/L-tryptophan treated wound dressing with P. aeruginosa biofilms were compared with untreated dressings. These findings indicate that tryptophan may prove useful for integration into wound dressings to inhibit biofilm formation and promote wound healing.

Inhibition of Pseudomonas aeruginosa with a recombinant RNA-based viral vector expressing human β-defensin 4

Background

Harassed with extensive epithelial burn wounds, patients can be affected by complications, such as infection, hypovolemic shock, hypothermia, and respiratory failure. Immediate first aid and followed supportive cares are critical for the prevention of severe complications. However, secondary bacterial infection is hard to be controlled in burn patients, and Pseudomonas aeruginosa (P. aeruginosa) is one of the top listed pathogens perturbing burn wounds beyond the antibiotics spectrum.

Results

To find the way for efficacious protection from the pseudomonas-mediated complications in burn patients, we assessed the in vitro and in vivo inhibitory values of human β-defensin 4 (hBD4), which is known as a member of the cationic, antimicrobial peptides found in human cells of many kinds. The Newcastle disease virus (NDV) was used as a viral vector for the expression of hBD4 in burn wounds. Expressed from the recombinant NDV (rNDV-hBD4), hBD4 effectively inhibited the pseudomonal growths in cell culture media. In a mouse model, severely burn-injured skin was recovered by the direct installation of the rNDV-hBD4 infected cells in the burn wounds whereas that of control mice remained severely damaged.

Conclusions

We suggest that the application of hBD4 may protect burn patients from secondary pseudomonal infection and provide a therapeutic potential for burn wound treatment.

Burn mouse models

Severe thermal injury induces immunosuppression, involving all parts of the immune system, especially when large fractions of the total body surface area are affected. An animal model was established to characterize the burn-induced immunosuppression. In our novel mouse model a 6 % third-degree burn injury was induced with a hot-air blower. The third-degree burn was confirmed histologically. At 48 h, a decline in the concentration of peripheral blood leucocytes was observed in the group of mice with burn wound. The reduction was ascribed to the decline in concentration of polymorphonuclear neutrophil leucocytes and monocytes. When infecting the skin with Pseudomonas aeruginosa, a dissemination of bacteria was observed only in the burn wound group. Histological characterization of the skin showed an increased polymorphonuclear neutrophil granulocytes dominated inflammation in the group of mice with infected burn wound compared with the burn wound only group. The burn mouse model resembles the clinical situation and provides an opportunity to examine or develop new strategies like new antibiotics and immune therapy, in handling burn wound victims much.

Polymicrobial wound infections: pathophysiology and current therapeutic approaches

Acute and chronic wounds represent a very common health problem in the entire world. The dermal wounds are colonized by aerobic and anaerobic bacterial and fungal strains, most of them belonging to the resident microbiota of the surrounding skin, oral cavity and gut, or from the external environment, forming polymicrobial communities called biofilms, which are prevalent especially in chronic wounds. A better understanding of the precise mechanisms by which microbial biofilms delay repair processes together with optimizing methods for biofilm detection and prevention may enhance opportunities for chronic wounds healing. The purpose of this minireview is to assess the role of polymicrobial biofilms in the occurrence and evolution of wound infections, as well as the current and future preventive and therapeutic strategies used for the management of polymicrobial wound infections.

Effect of Radiofrequency Ablation on Healing of Infected Full-Thickness Wounds in Minipigs

The success of debridement is critical to optimize the treatment outcomes of traumatic wounds. To investigate the impact of radiofrequency ablation on healing potential of infected wounds, minipigs with infected full-thickness skin defects on backs were divided into 4 treatment groups randomly: radiofrequency ablation debridement, electric knife debridement, sharp instrument debridement, and no treatment. The healing rate, healing time, tissue filling rate, bacterial quantitative, and histological assay were evaluated postoperatively. The results obtained provide evidence that the wounds after radiofrequency ablation treatment enhanced the skin wound-healing efficacy and had better outcomes of tissue filling compared with other debridement therapies. Furthermore, we quantified the bacterial counting level in wound samples, and the results revealed a more significant decreasing trend in radiofrequency ablation group than that of the electric knife debridement group and the sharp instrument debridement group. Postoperative histological measurements showed that there were better granulation formation and re-epithelialization and collagen deposition in radiofrequency ablation–treated wounds than those in other groups. The present findings demonstrate that radiofrequency ablation has a significantly influence on reducing the number of bacteria and improving the healing quality and is a promising candidate for treatment of infected wounds.

Comparing the hydrosurgery system to conventional debridement techniques for the treatment of delayed healing wounds: a prospective, randomised clinical trial to investigate clinical efficacy and cost-effectiveness

In these uncertain times of high health care costs, clinicians are looking for cost-effective devices to employ in their everyday practices. In an effort to promote cost-effective and proper wound repair, the hydrosurgical device allows accurate debridement of only unwanted tissue while precisely conserving viable structures for eventual repair. This prospective, randomised study compared procedures using the hydrosurgery system (VERSAJET™) with conventional debridement in order to assess clinical efficacy and cost-effectiveness when treating subjects with chronic wounds. A total of 40 subjects were recruited. There was no difference in time to achieve stable wound closure between the treatment groups (P = 0·77). There were no significant differences between the two groups in terms of cost of the first operative procedure (P = 0·28), cost of surgical procedures during the study (P = 0·51), cost of study treatment (P = 0·29) or cost to achieve stable wound closure (P = 0·85). There were no differences in quantitative bacterial counts after debridement with either methods (P = 0·376). However, the time taken for the first excision procedure was significantly faster using the hydrosurgery system (VERSAJET) when compared with conventional debridement (P < 0·001). The total excision time for all procedures was significantly less for the Hydrosurgery group than for the conventional group (P = 0·005). Also, the Hydrosurgery group demonstrated significantly less intraoperative blood loss than conventional group for all procedures (P = 0·003). In this study, although there were no differences in time to stable wound closure or bacterial reduction between the two groups, the hydrosurgery system (VERSAJET) did offer advantages in terms of operative times and intraoperative blood loss and was cost-neutral, despite the handpiece cost.

Erosive pustular dermatosis (chronic atrophic dermatosis of the scalp and extremities)

Erosive pustular dermatosis is a rare noninfectious disease of the scalp or legs. Clinical findings are nonspecific, with crusts, atrophy, and pustules. A later complication of erosive pustular dermatosis is secondary cicatrical alopecia. The list of possible differential diagnoses is long, and includes infectious, inflammatory, and neoplastic dermatoses. Treatment is challenging. Topical drug therapy may improve the condition, but rarely results in a complete resolution. Surgery has been linked to exacerbation in some patients. In our hands, it achieved complete remission in male patients.

Wound biofilms: lessons learned from oral biofilms

Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

Interactions of methicillin resistant Staphylococcus aureus USA300 and Pseudomonas aeruginosa in polymicrobial wound infection

Understanding the pathology resulting from Staphylococcus aureus and Pseudomonas aeruginosa polymicrobial wound infections is of great importance due to their ubiquitous nature, increasing prevalence, growing resistance to antimicrobial agents, and ability to delay healing. Methicillin-resistant S. aureus USA300 is the leading cause of community-associated bacterial infections resulting in increased morbidity and mortality. We utilized a well-established porcine partial thickness wound healing model to study the synergistic effects of USA300 and P. aeruginosa on wound healing. Wound re-epithelialization was significantly delayed by mixed-species biofilms through suppression of keratinocyte growth factor 1. Pseudomonas showed an inhibitory effect on USA300 growth in vitro while both species co-existed in cutaneous wounds in vivo. Polymicrobial wound infection in the presence of P. aeruginosa resulted in induced expression of USA300 virulence factors Panton-Valentine leukocidin and α-hemolysin. These results provide evidence for the interaction of bacterial species within mixed-species biofilms in vivo and for the first time, the contribution of virulence factors to the severity of polymicrobial wound infections.

New techniques for wound debridement

Debridement is a crucial component of wound management. Traditionally, several types of wound debridement techniques have been used in clinical practice such as autolytic, enzymatic, biodebridement, mechanical, conservative sharp and surgical. Various factors determine the method of choice for debridement for a particular wound such as suitability to the patient, the type of wound, its anatomical location and the extent of debridement required. Recently developed products are beginning to challenge traditional techniques that are currently used in wound bed preparation. The purpose of this review was to critically evaluate the current evidence behind the use of these newer techniques in clinical practice. There is some evidence to suggest that low frequency ultrasound therapy may improve healing rates in patients with venous ulcers and diabetic foot ulcers. Hydrosurgery debridement is quick and precise, but the current evidence is limited and further studies are underway. Debridement using a monofilament polyester fibre pad and plasma-mediated bipolar radiofrequency ablation are both very new techniques. The initial evidence is limited, and further studies are warranted to confirm their role in management of chronic wounds.

Coblation Technology for Surgical Wound Debridement

Debridement is required to prepare the wound bed, essentially in removing undesired tissues observed both in acute wound after burns or trauma and in chronic wounds such as pressure ulcers, leg ulcers, and diabetic foot ulcers. Surgical debridement has been described as one of the most effective methods but can be contraindicated in the elderly, arteriopathic context, or patients under effective anticoagulation. Recently described debridement technologies are based on application of important mechanical severing forces over the wound surface using high-power hydrojets. High water flux acts as a vector for separating necrotic and sloughy tissues from the wound bed and aspirates them out of the wound immediately. Electrical powered techniques and lasers were also scarcely described. The Coblation debridement technology presented here is based on the local induction of a focused plasma field chemically deleting undesired tissues. This technique is a modification of conventional electrosurgical devices, developed in 1928 where tissue excision and coagulation of tissues were observed. Principles of plasma-mediated debridement are based on a bipolar radiofrequency energizing the molecules, thus creating a plasma field. This glow discharge plasma produces chemically active radical species from dissociation of water, breaking molecular bonds, and causing tissue dissolution. The thermal effects are a by-product, which can be modulated by modifying the electrode construction, limiting the local temperature to less than 50°C in order not to induce wound bed renecrosis. The authors describe here the principle, the first technical adaptation for wound debridement, and the potential clinical interest of the Coblation technology