The use of desiccation to treat Staphylococcus aureus biofilm-infected wounds

Glycerol and Antimicrobial Peptide-Modified Natural Latex for Bacteriostasis of Skin Wounds

This work aimed to develop a glycerol antimicrobial peptide natural latex film (NRL-GI-AMP film) for the treatment of skin wound infections. The contents of this work mainly include investigating the effect of adding glycerol (GI) and an antimicrobial peptide (AMP) on the physical and chemical properties of natural latex (NRL) and analyzing the cytocompatibility, bacteriostatic activity, and infected wound healing promotion of the NRL-GI-AMP film. The results showed that the addition of GI resulted in more pores in the internal structure of the NRL film, while the addition of G(LLKK)₃L AMP did not change the structure and properties of the NRL film. Compared with that of the NRL film, the infrared spectrum of the NRL-GI-AMP film did not produce new characteristic peaks, indicating that GI and AMP were non-covalently cross-linked with NRL. Addition of 10% GI reduces the toughness of the NRL-GI-AMP film by 62.0%, increases the water vapor transmission rate by 8.95 mg/(cm²·h), and reduces the water absorption and water retention distributions by 33.0 and 24.7%, respectively. AMP in the NRL-GI-AMP film could be released continuously for 40 h, and the release rate was about 45%. The NRL-GI-AMP film showed good biocompatibility and antibacterial activity and promoted the healing of infected wounds. Therefore, the NRL-GI-AP film has potential application in the development of dressings to inhibit skin wound infection and promote 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.

Re-thinking lactation-related nipple pain and damage

Nipple pain is a common reason for premature cessation of breastfeeding. Despite the benefits of breastfeeding for both infant and mother, clinical support for problems such as maternal nipple pain remains a research frontier. Maternal pharmaceutical treatments, and infant surgery and bodywork interventions are commonly recommended for lactation-related nipple pain without evidence of benefit. The pain is frequently attributed to mammary dysbiosis, candidiasis, or infant anatomic anomaly (including to diagnoses of posterior or upper lip-tie, high palate, retrognathia, or subtle cranial nerve abnormalities). Although clinical protocols universally state that improved fit and hold is the mainstay of treatment of nipple pain and wounds, the biomechanical parameters of pain-free fit and hold remain an omitted variable bias in almost all clinical breastfeeding research. This article reviews the research literature concerning aetiology, classification, prevention, and management of lactation-related nipple-areolar complex (NAC) pain and damage. Evolutionary and complex systems perspectives are applied to develop a narrative synthesis of the heterogeneous and interdisciplinary evidence elucidating nipple pain in breastfeeding women. Lactation-related nipple pain is most commonly a symptom of inflammation due to repetitive application of excessive mechanical stretching and deformational forces to nipple epidermis, dermis and stroma during milk removal. Keratinocytes lock together when mechanical forces exceed desmosome yield points, but if mechanical loads continue to increase, desmosomes may rupture, resulting in inflammation and epithelial fracture. Mechanical stretching and deformation forces may cause stromal micro-haemorrhage and inflammation. Although the environment of the skin of the nipple-areolar complex is uniquely conducive to wound healing, it is also uniquely exposed to environmental risks. The two key factors that both prevent and treat nipple pain and inflammation are, first, elimination of conflicting vectors of force during suckling or mechanical milk removal, and second, elimination of overhydration of the epithelium which risks moisture-associated skin damage. There is urgent need for evaluation of evidence-based interventions for the elimination of conflicting intra-oral vectors of force during suckling.

Efficacy of a Topical Wound Agent Methanesulfonic Acid and Dimethylsulfoxide on In Vitro Biofilms

A topical desiccating wound agent containing methanesulfonic acid, dimethylsulfoxide and amorphous silica was evaluated in three in vitro models for its efficacy against biofilms produced by Pseudomonas aeruginosa (ATCC-15442) and Staphylococcus aureus (ATCC-6538). The in vitro biofilm models used were; the MBEC Assay^®, Centre for Disease Control (CDC) Biofilm Reactor^® and a Semi-solid biofilm model. A 30-s exposure of a topical wound desiccating agent was used in each model. A complete eradication of viable cells was demonstrated in all models for both strains (p < 0.0001). Imaging with scanning electron microscopy (SEM) was performed where possible. All three models demonstrated complete eradication of viable cells with a 30 s application of a topical wound desiccating agent.

In vitro Evaluation of Medihoney Antibacterial Wound Gel as an Anti-biofilm Agent Against Ventricular Assist Device Driveline Infections

Objectives: In adult ventricular assist device (VAD) programs in Australian hospitals, Medihoney Antibacterial Wound Gel (MAWG) is routinely used at the skin exit-site of VAD drivelines to prevent infections; however, its effectiveness remains unclear. Our aim was to assess antimicrobial activity of Medihoney wound gel, using in vitro models that mimic clinical biofilms grown at the driveline exit-site. Methods: Antimicrobial susceptibility testing of MAWG was performed for 24 clinical isolates grown under planktonic conditions, and four representative strains grown as biofilms. Different antimicrobial mechanisms of MAWG were assessed respectively for their relative contribution to its anti-biofilm activity. A colony biofilm assay and a drip-flow biofilm reactor assay mimicking the driveline exit-site environment were used to evaluate the activity of MAWG against biofilm growth at the driveline exit-site. Results: MAWG demonstrated species-specific activity against planktonic cultures [minimum inhibitory concentrations (MICs), 5-20% weight/volume (W/V) for Staphylococcus species, 20->40% (W/V) for Pseudomonas aeruginosa and Candida species]. Higher concentrations [MICs, 30->80% (W/V)] were able to inhibit biofilm growth, but failed to eradicate pre-established biofilms. The anti-biofilm properties of MAWG were multi-faceted, with the often-advertised "active" ingredient methylglyoxal (MGO) playing a less important role. The colony biofilm assay and the drip-flow biofilm reactor assay suggested that MAWG was unable to kill biofilms pre-established in a driveline exit-site environment, or effectively prevent planktonic cells from forming adherent monolayers and further developing mature biofilms. Conclusion: Our work suggests a suboptimal effectiveness of MAWG in preventing driveline infections due to biofilm development.

The efficacy of topical agents used in wounds for managing chronic biofilm infections: A systematic review

OBJECTIVES

Clinicians have increasingly adopted the widespread use of topical agents to manage chronic wound infections, despite limited data on their effectiveness in vivo. This study sought to evaluate the evidence for commonly employed topical agents used in wounds for the purpose of treating chronic infections caused by biofilm.

METHOD

We included in vitro, animal and human in vivo studies where topical agents were tested for their efficacy against biofilms, for use in wound care. For human studies, we only included those which utilised appropriate identification techniques for visualising and confirming the presence of biofilms.

RESULT

A total of 640 articles were identified, with 43 included after meeting eligibility. In vitro testing accounted for 90% (n = 39) of all included studies, five studies using animal models and three human in vivo studies. Sixteen different laboratory models were utilised, with the most frequent being the minimum biofilm eradication concentration (MBEC™) / well plate assay (38%, n = 15 of 39). A total of 44 commercially available topical agents were grouped into twelve categories with the most commonly tested agents being silver, iodine and polyhexamethylene biguanide (PHMB). In vitro results on efficacy demonstrated iodine as having the highest mean log10 reductions of all agents (4.81, ±3.14).

CONCLUSION

There is large disparity in the translation of laboratory studies to researchers undertaking human trials relating to the effectiveness of commercially available topical agents. There is insufficient human in vivo evidence to definitively recommend any commercially available topical agent over another for the treatment of chronic wound biofilms. The heterogeneity identified between study designs (in vitro to in vivo) further limits the generalisability of results.

Clinical investigation of biofilm in non-healing wounds by high resolution microscopy techniques

OBJECTIVE

The aim of this study was to analyse wound biofilm from a clinical perspective. Research has shown that biofilm is the preferred microbial phenotype in health and disease and is present in a majority of chronic wounds. Biofilm has been linked to chronic wound inflammation, impairment in granulation tissue and epithelial migration, yet there lacks the ability to confirm the clinical presence of biofilm. This study links the clinical setting with microscopic laboratory confirmation of the presence of biofilm in carefully selected wound debridement samples.

METHOD

Human wound debridement samples were collected from adult patients with chronic non-healing wounds who presented at the wound care centre. Sample choice was guided by an algorithm that was developed based on what is known about the characteristics of wound biofilm. The samples were then evaluated by light microscopy and scanning electron microscopy for the presence of biofilm. Details about subject history and treatment were recorded. Adherence to biofilm-based wound care (BBWC) strategies was inconsistent. Other standard antimicrobial dressings were used and no modern antiseptic wound dressings with the addition of proven antibiofilm agents were available for use.

RESULTS

Of the patients recruited, 75% of the macroscopic samples contained biofilm despite the prior use of modern antiseptic wound dressings and in some cases, systemic antibiotics. Wounds found to contain biofilm were not all acutely infected but biofilm was present when infection was noted. The clinical histories associated with positive samples were consistent with ideas presented in the algorithm used to guide sample selection.

CONCLUSION

Visual cues can be used by the clinician to guide suspicion of the presence of wound biofilm. This suspicion can be further enhanced with the use of a clinical algorithm. Standard antiseptic wound dressings used in this study demonstrated limited antibiofilm efficacy. This study also highlighted a need for the clinical team to focus on expiration of dressing action and consistent practice of BBWC strategies which includes the use of proven antibiofilm agents.

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.

The occurrence of biofilm in an equine experimental wound model of healing by secondary intention

In humans, biofilm is a well-known cause of delayed healing and low-grade inflammation of chronic wounds. In horses, biofilm formation in wounds has been studied to a very limited degree. The objective of this study was thus to investigate the occurrence of biofilm in equine experimental wounds healing by secondary intention. Tissue biopsies from non-contaminated, experimental excisional shoulder and limb wounds were obtained on day 1-2, day 7-10 and day 14-15 post-wounding. Limb wounds were either un-bandaged or bandaged to induce exuberant granulation tissue (EGT) formation and thereby impaired healing. Presence of biofilm in tissue biopsies was assessed by peptide nucleic acid fluorescence in situ hybridization (PNA FISH) and confocal laser scanning microscopy (CLSM). Bandaged limb wounds developed EGT and displayed delayed healing, while shoulder and un-bandaged limb wounds healed normally. Biofilm was detected in limb wounds only. At day 14-15 biofilm was significantly more prevalent in bandaged limb wounds than in un-bandaged limb wounds (P=0.003). Further, bandaged limb wounds had a statistically significant increase in biofilm burden from day 7-10 to day 14-15 (P=0.009). The finding that biofilm was most prevalent in bandaged limb wounds with EGT formation suggests that biofilm may be linked to delayed wound healing in horses, as has been observed in humans. The inability to clear bacteria could be related to hypoxia and low-grade inflammation in the EGT, but the interaction between biofilm forming bacteria and wound healing in horses needs further elucidation.