Approach to chronic wound infections.

The occurrence of chronic wounds is a major global health issue. These wounds are difficult to heal as a result of disordered healing mechanisms. The most common types of chronic wounds are diabetic ulcers, pressure ulcers, arterial/venous ulcers and nonhealing surgical wounds. Although bacteria are an important cause of chronic nonhealing wounds, fungi also play a substantial role in them. The fungal infection rate varies with different chronic wound types, but overall, the prevalence of fungi is extremely underestimated in the clinical treatment and management of chronic wounds. Wounds and ulcers can be colonized by host cutaneous, commensal or environmental fungi and evolve into local infections, causing fungemia as well as invasive fungal disease. Furthermore, the fungi involved in nonhealing wound-related infections help commensal bacteria resist antibiotics and the host immune response, forcing wounds to become reservoirs for multiresistant species, which are considered a potential key factor in the microbial bioburden of wounds and ulcers. Fungi can be recalcitrant to the healing process. Biofilm establishment is the predominant mechanism of fungal resistance or tolerance to antimicrobials in chronic nonhealing wounds. Candida albicans yeast and Trichophyton rubrum filamentous fungi are the main fungi involved in chronic wound infection. Fungal species diversity and drug resistance phenotypes in different chronic nonhealing wound types will be emphasized. In this review, we outline the latest research on fungi in chronic wounds and discuss challenges and future perspectives related to diagnosing and managing chronic wounds.

We sought to examine whether vacuum-assisted closure (VAC) is associated with fewer surgical site infections (SSIs) or infections of chronic wounds than other management procedures for surgical wounds. The PubMed and Scopus databases were searched systematically. Randomized controlled trials (RCTs) comparing the development of SSIs or infections of chronic wounds between patients treated with VAC for acute or chronic wounds and those whose wounds were treated without VAC were considered eligible for inclusion in the study. Eight RCTs met the inclusion criteria for the study. Four of the studies included chronic or diabetic lower extremity wounds and four included fractures. In three of four studies reporting on fractures, the wounds were not closed post-operatively, whereas in one study primary closure of the wound was performed. With regard to wounds left open after the stabilization of fractures, patients whose wounds were treated with VAC developed fewer SSIs than those whose wounds were treated without VAC ([367 patients (196 with VAC; 171 without VAC) relative risk [RR], 0.47; 95% CI 0.28-0.81]). On the contrary, no difference in the development of SSIs occurred among patients with chronic or diabetic lower-extremity wounds treated with VAC and those whose wounds were treated without VAC ([638 patients (320 with VAC; 318 without VAC) RR 1.67; 95% CI: 0.71-3.94]). The available evidence suggests that the development of infections in wounds treated with VAC depends on the type of wound being treated.

Increased local temperature is a classic sign of wound infection, and its quantitative measurement has the potential to assist with assessment and diagnosis of chronic deep wound and surrounding skin infection at the bedside. Evidence supporting such use in chronic wound care is very limited. This clinical pilot study was conducted in an attempt to quantify the relationship between increased periwound skin temperature and wound infection, as well as validate use of a handheld infrared thermometer for the wound care practitioner. Using a cross-sectional design, 2 groups of participants were recruited from a chronic wound clinic: without wounds (n = 20) and with chronic leg ulcers (n = 40). Participant and wound characteristics were documented. All skin temperatures were documented using a handheld infrared thermometer under consistent environmental conditions within the clinic. Data analysis was based on the difference (Delta) in skin temperature (in degrees Fahrenheit) between a target or wound site and an equivalent contralateral control site. Wound infection was identified using the combination of a validated assessment tool and clinical judgment. Supplemental semiquantitative bacterial swabs were collected from all wounds. Descriptive statistics were analyzed using the chi-squared calculation. A Pearson r calculation of test-retest skin temperature data collected from nonwounded participants initially determined reliability of the infrared thermometer. Correlation of increased periwound skin temperature to wound infection was determined by calculation of a 1-way analysis of variance. The infrared thermometer was found to be reliable (r = 0.939, P = .000 at a 95% confidence interval). A statistically significant relationship between increased periwound skin temperature and wound infection was identified (F = 44.238, P = .000 at a 95% confidence interval). Neither patient nor wound characteristics were significantly different between the participants with noninfected or infected wounds. The results of this study demonstrate that incorporating quantitative skin temperature measurement into routine wound assessment provides a timely and reliable method for a wound care practitioner to quantify the heat associated with deep and surrounding skin infection and to monitor ongoing wound status. Study limitations may reduce transferability of these findings to wound types other than chronic leg ulcers. Further research is needed to support and strengthen these results.

Biofilms in Chronic Wounds: Pathogenesis and Diagnosis

Objective: Autologous platelet rich plasma is an advanced wound therapy used in hard-to-heal acute and chronic wounds. To better understand the use and clinical outcomes of the therapy, a systematic review of the published literature in cutaneous wounds was performed. Methods: Electronic and hand searches for randomized controlled trials and comparative group studies using platelet rich plasma therapy in cutaneous wounds and published over the last 10 years was conducted. Eligible studies compared the treatment to standard care or other interventions. All citations were screened and eligible studies were assessed for validity, quality, and bias using accepted scoring methods. The primary outcomes were effect of platelet rich plasma and control wound care on wound healing and related healing measurements. Secondary outcomes related to healing such as infection, pain, exudate, adverse events, and quality of life were also considered. The meta-analysis utilized appropriate statistical methods to determine the overall treatment effect on chronic and acute wound healing and infection. Results: The search terms resulted in 8577 citations and after removing duplicates and screening for protocol eligibility, a total of 24 papers were used. The meta-analysis of chronic wound studies revealed platelet rich plasma therapy is significantly favored for complete healing. The meta-analysis of acute wounds with primary closure studies demonstrated that presence of infection was reduced in platelet rich plasma treated wounds. Conclusions: This systematic review and meta-analysis of platelet rich plasma therapy in cutaneous wounds showed complete and partial wound healing was improved compared to control wound care.

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.

Introduction: Prevention and management of biofilm in acute and chronic wounds in ICU settings is critical, as biofilm significantly impedes wound healing. Approximately 90% of all wounds are affected by biofilm. It is not feasible to eliminate biofilm using a single wound-cleaning technology. Early intervention and the combined use of multiple technologies for biofilm removal are essential to promote wound healing. Rapid and effective treatment is vital to prevent severe complications such as infections or amputations in intensive care units. Drawing on extensive knowledge of available technologies and their mechanisms of action, we adopted a multimodal approach to treat wounds with biofilm. The primary objective was to prevent and manage biofilm in both acute and chronic wounds. Methods: Five patients with infected acute and traumatic wounds—including chronic osteomyelitis tunnel wound, gunshot injuries, shrapnel wounds, surgical incisions, and fasciotomies—underwent Three-Step Multimodal Biofilm-Focused Protocol consisting of three sequential steps: Step 1: Cleansing and moistening wounds with a solution containing active pure HOCl (pH 2.5) for at least 30 minutes. Step 2: Cleansing and moistening wounds with a polyhexamethylene biguanide (PHMB) and betaine solution, left in place for 30 minutes, followed by cleaning with a debridement pad. Step 3: Application of a synergistic ionic silver (0.01%)–menthol liquid dressing with unique properties (cleansing, disinfecting, removing waste and slough, destroying biofilm). This dressing offers broad-spectrum antibacterial activity and accelerates healing. Wet pads were left in the wounds for the remainder of the day. Results / Discussion: All wounds demonstrated improvement, with the formation of new granulation tissue. Subsequent treatments included negative pressure therapy, secondary surgical closure, or skin grafting. Gunshot and shrapnel wounds healed successfully, limb amputation was avoided, and the chronic osteomyelitis tunnel wound contracted. This Three-Step Multimodal Biofilm-Focused Protocol enhanced wound healing, prevented amputations, and accelerated recovery. The method was later applied to other complex wounds in ICU patients.

The role of proteases in chronic wounds has been the subject of many investigations in recent years. These studies have reported biochemical differences between chronic and acute wound fluids and have shown that elevated levels of proteases, in particular the matrix metalloproteinases are abundant in chronic wounds. While this has led to the hypothesis that the chronic wound environment is hostile and not conducive to wound repair, it is still unknown whether this is due to a direct or indirect defect in protease regulation or their inhibitors. We hypothesize that an excess of proteases, specifically the serine proteases present in chronic wounds, are primarily responsible for this hostile wound environment. These proteases degrade endogenous growth factors, reducing their efficacy and delaying healing. In this study, fluid and tissue from chronic and acute wounds were collected over a 24-hour period. Using ELISA, samples were assessed for protease activity (specifically elastase and typsin-like enzymes), their inhibitors and growth factors. Our results show that serine proteases, predominantly elastase, were significantly elevated in the chronic wound fluids. The serpins designed to control these proteases were not up-regulated when compared to the acute controls, resulting in excessive proteolytic activity. An increase in serine protease production without an increase in their serpins is thought to result in a reduction in growth factors, an effect, which was also observed in the chronic wound samples. This work indicates that there is an imbalance in the ratio of inhibitor to enzyme, due to an up regulation of protease production in chronic wounds. We also conclude that misregulation of serine proteases may be responsible for the observed excessive degradation of the extracellular matrix and growth factors in these chronic wounds.

Introduction. Chronic wounds are notoriously difficult to treat and are associated with decreased limb function, reduced quality of life and significant morbidity. Their recurrent nature, despite aggressive antibiotic therapy, is due in part to the presence of polymicrobial biofilms. Pseudomonas aeruginosa and Staphylococcus aureus are two of the most frequently co-isolated pathogens in these infections and are known to form complex biofilms that hinder treatment.Hypothesis. We hypothesized that co-existence and competitive dynamics between P. aeruginosa and S. aureus in chronic wound infections are influenced by strain-specific interactions and may not rely solely on well-characterized inhibitory mechanisms such as 2-alkyl-4-quinolone (AQ) production by P. aeruginosa impacting on S. aureus fitness.Aim. To establish a polymicrobial chronic wound infection model and assess the contribution of AQ signalling and strain-specific interactions on co-existence.Methodology. We used a modified chronic wound biofilm model to co-culture matched and mismatched clinical isolate pairs of P. aeruginosa and S. aureus, collected from two different chronic wound patients. Viable bacterial counts (c.f.u.) were quantified over an 8-day period. AQ production by each P. aeruginosa strain was quantified using liquid chromatography-MS.Results. A stable culture of P. aeruginosa strains was achieved, but distinct behaviours between each S. aureus strain were seen. One matched clinical isolate pair maintained stable c.f.u. levels of both species throughout the 8-day model, indicating a compatible co-existence. In contrast, mismatched pairs showed early loss of S. aureus viability and the emergence of small colony variants after 4 days, not seen in matched pair growth. Interestingly, the most competitive P. aeruginosa strain exhibited undetectable levels of all AQs tested, indicating that its dominance was not due to AQ-mediated antagonism, as has previously been described.Conclusion. Our findings demonstrate that stable dual-species biofilm formation in chronic wounds is strain-dependent and that P. aeruginosa can impact on S. aureus fitness through AQ-independent mechanisms. These results highlight the importance of using clinical isolates in biofilm research and caution against generalizing findings from laboratory strains to complex clinical infections.

Exogenously applied transforming growth factor-beta (TGF-beta) isoforms enhance wound healing processes in animal models; however, little is known about the expression of endogenous TGF-beta s and TGF-beta receptors in intact human skin or during wound healing. The present study has revealed several unexpected findings by means of in situ hybridization and immunohistology techniques. In humans, TGF-beta 3 is constitutively expressed in the epidermis of intact skin and in that of acute and chronic wounds--a pattern of expression closely mirrored by the TGF-beta type II receptor. Although not detected in intact skin, TGF-beta 1 mRNA expression was observed in the regenerating epidermis of acute (thermal) wounds but was not found in chronic decubital (pressure) wounds. TGF-beta 2 mRNA expression was not detected in the epidermis of any human skin or wound biopsies. From these findings we suggest that constitutive expression of TGF-beta 3 is important for maintenance of epidermal differentiation and that an induction of TGF-beta 1 expression is essential for re-epithelialization of human skin wounds. Lack of TGF-beta 1 expression in chronic pressure wounds may be associated with their protracted healing tendencies.

Wound healing is a complex multiphase process which can be hampered by many factors including impaired local circulation, hypoxia, infection, malnutrition, immunosuppression, and metabolic dysregulation in diabetes. Redox dysregulation is a common feature of many skin diseases demonstrated by virtually all cell types in the skin with overproduction of reactive oxygen and nitrogen species. The objective of this study was to characterize the redox environment in wound fluids and sera from patients suffering from chronic leg ulcers (n = 19) and acute wounds (bulla fluids from second degree burns; n = 11) with serum data also compared to those from healthy volunteers (n = 7). Significantly higher concentrations of TNF-α, interleukine-8, vascular endothelial growth factor, and lactate dehydrogenase (measure of cell damage) were found in fluids from chronic wounds compared to acute ones. The extent of protein carbonylation (measure of protein oxidation), lipid peroxidation, and tyrosine nitration (indicator of peroxynitrite production) was similar in acute and chronic wound fluids, while radical scavenging activity and glutathione (GSH) levels were elevated in chronic wound fluids compared to acute wounds. Sera were also assessed for the same set of parameters with no significant differences detected. Nitrotyrosine (the footprint of the potent oxidant peroxynitrite) and poly(ADP-ribose) (the product of the DNA damage sensor enzyme PARP-1) could be detected in wound biopsies. Our data identify multiple signs of redox stress in chronic wounds with notable differences. In chronic wounds, elevations in antioxidant levels/activities may indicate compensatory mechanisms against inflammation. The presence of nitrotyrosine and poly(ADP-ribose) in tissues from venous leg ulcers indicate peroxynitrite production and PARP activation in chronic wounds.

While much is known about acute infection pathogenesis, the understanding of chronic infections has lagged. Here we sought to identify the genes and functions that mediate fitness of the pathogen Pseudomonas aeruginosa in chronic wound infections, and to better understand the selective environment in wounds. We found that clinical isolates from chronic human wounds were frequently defective in virulence functions and biofilm formation, and that many virulence and biofilm formation genes were not required for bacterial fitness in experimental mouse wounds. In contrast, genes involved in anaerobic growth, some metabolic and energy pathways, and membrane integrity were critical. Consistent with these findings, the fitness characteristics of some wound impaired-mutants could be represented by anaerobic, oxidative, and membrane-stress conditions ex vivo, and more comprehensively by high-density bacterial growth conditions, in the absence of a host. These data shed light on the bacterial functions needed in chronic wound infections, the nature of stresses applied to bacteria at chronic infection sites, and suggest therapeutic targets that might compromise wound infection pathogenesis.

Chronic wound infections are an important cause of delayed wound healing, posing a significant healthcare burden with consequences that include hospitalization, amputation, and death. These infections most often take the form of three-dimensional biofilm communities, which are notoriously recalcitrant to antibiotics and immune clearance, contributing to the chronic wound state. In the chronic wound microenvironment, microbial biofilms interact closely with other key components, including host cellular and matrix elements, immune cells, inflammatory factors, signaling components, and mechanical cues. Intricate relationships between these contributing factors not only orchestrate the development and progression of wound infections but also influence the therapeutic outcome. Current medical treatment for chronic wound infections relies heavily on long-term usage of antibiotics; however, their efficacy and reasons for failure remain uncertain. To develop effective therapeutic approaches, it is essential to better understand the complex pathophysiology of the chronic wound infection microenvironment, including dynamic interactions between various key factors. For this, it is critical to develop bioengineered platforms or model systems that not only include key components of the chronic wound infection microenvironment but also recapitulate interactions between these factors, thereby simulating the infection state. In doing so, these platforms will enable the testing of novel therapeutics, alone and in combinations, providing insights toward composite treatment strategies. In the first section of this review, we discuss the key components and interactions in the chronic wound infection microenvironment, which would be critical to recapitulate in a bioengineered platform. In the next section, we summarize the key features and relevance of current bioengineered chronic wound infection platforms. These are categorized and discussed based on the microenvironmental components included and their ability to recapitulate the architecture, interactions, and outcomes of the infection microenvironment. While these platforms have advanced our understanding of the underlying pathophysiology of chronic wound infections and provided insights into therapeutics, they possess certain insufficiencies that limit their clinical relevance. In the final section, we propose approaches that can be incorporated into these existing model systems or developed into future platforms developed, thus enhancing their biomimetic and translational capabilities, and thereby their human-relevance.

To evaluate the efficacy of an enzyme alginogel in outpatients with chronic or acute wounds left to heal by secondary intention. This evaluation was a single-centre, single-arm, case series involving 23 patients with wounds of diverse aetiologies treated with the enzyme alginogel (Flaminal; Flen Pharma). The product was applied in accordance with the manufacturer's instructions and wounds were covered with secondary dressings. Treatment was based on a scheduled protocol and patients were assessed at days 14, 30 and 60. Median baseline dimensions for the wounds were surface area 2.6cm2 and volume 2.8cm3. Median wound duration before application of the enzyme alginogel was 292 days, with 16 chronic wounds (78%). Three wounds were clinically infected at baseline; two were negative by day 14 and the third by day 30. After 2 months, wound surface area and volume had decreased, as could be expected. Two adverse events were reported: an allergic reaction in the skin surrounding the wound and transient maceration. The enzyme alginogel facilitated healing in chronic and acute wounds of diverse aetiologies. Additional research is warranted to confirm the clinical utility of the dressings in the management of chronic or acute wounds left to heal by secondary intention.

Generally, wounds are of two categories, such as chronic and acute. Chronic wounds takes time to heal when compared to the acute wounds. Chronic wounds include vasculitis, non healing ulcer, pyoderma gangrenosum, and diseases that cause ischemia. Chronic wounds are rapidly increasing among the elderly population with dysfunctional valves in their lower extremity deep veins, ulcer, neuropathic foot and pressure ulcers. The process of the healing of wounds has several steps with the involvement of immune cells and several other cell types. There are many evidences supporting the hypothesis that apoptosis of immune cells is involved in the wound healing process by ending inflammatory condition. It is also involved in the resolution of various phases of tissue repair. During final steps of wound healing most of the endothelial cells, macrophages and myofibroblasts undergo apoptosis or exit from the wound, leaving a mass that contains few cells and consists mostly of collagen and other extracellular matrix proteins to provide strength to the healing tissue. This review discusses the various phases of wound healing both in the chronic and acute wounds especially during diabetes mellitus and thus support the hypothesis that the oxidative stress, apoptosis, connexins and other molecules involved in the regulation of chronic wound healing in diabetes mellitus and gives proper understanding of the mechanisms controlling apoptosis and tissue repair during diabetes and may eventually develop therapeutic modalities to fasten the healing process in diabetic patients.