Wound fluid lactate concentration: a helpful marker for diagnosing soft-tissue infection in diabetic foot ulcers? Preliminary findings

Which biomarkers predict hard-to-heal diabetic foot ulcers? A scoping review

Diabetic foot ulcers (DFUs) often develop into hard-to-heal wounds due to complex factors. Several biomarkers capable of identifying those at risk of delayed wound healing have been reported. Controlling or targeting these biomarkers could prevent the progression of DFUs into hard-to-heal wounds. This scoping review aimed to identify the key biomarkers that can predict hard-to-heal DFUs. Studies that reported biomarkers related to hard-to-heal DFUs, from 1980 to 2023, were mapped. Studies were collected from the following databases: MEDLINE, CINAHL, EMBASE, and ICHUSHI (Japana Centra Revuo Medicina), search terms included "diabetic," "ulcer," "non-healing," and "biomarker." A total of 808 articles were mapped, and 14 (10 human and 4 animal studies) were included in this review. The ulcer characteristics in the clinical studies varied. Most studies focused on either infected wounds or neuropathic wounds, and patients with ischemia were usually excluded. Among the reported biomarkers for the prediction of hard-to-heal DFUs, the pro-inflammatory cytokine CXCL-6 in wound fluid from non-infected and non-ischemic wounds had the highest prediction accuracy (area under the curve: 0.965; sensitivity: 87.27%; specificity: 95.56%). CXCL-6 levels could be a useful predictive biomarker for hard-to-heal DFUs. However, CXCL6, a chemoattractant for neutrophilic granulocytes, elicits its chemotactic effects by combining with the chemokine receptors CXCR1 and CXCR2, and is involved in several diseases. Therefore, it's difficult to use CXCL6 as a prevention or treatment target. Targetable specific biomarkers for hard-to-heal DFUs need to be determined.

Quantitative Insights and Visualization of Antimicrobial Tolerance in Mixed-Species Biofilms

Biofilms are a major problem in hard-to-heal wounds. Moreover, they are composed of different species and are often tolerant to antimicrobial agents. At the same time, interspecific synergy and/or competition occurs when some bacterial species clash. For this reason, the tolerance of two dual-species wound biofilm models of Pseudomonas aeruginosa and Staphylococcus aureus or Enterococcus faecium against antimicrobials and antimicrobial dressings were analyzed quantitatively and by confocal laser scanning microscopy (CLSM). The results were compared to findings with planktonic bacteria. Octenidine-dihydrochloride/phenoxyethanol and polyhexamethylene biguanide (PHMB) irrigation solutions showed a significant, albeit delayed reduction in biofilm bacteria, while the PHMB dressing was not able to induce this effect. However, the cadexomer-iodine dressing caused a sustained reduction in and killed almost all bacteria down to 102 cfu/mL within 6 days compared to the control (1010 cfu/mL). By means of CLSM in untreated human biofilm models, it became evident that P. aeruginosa dominates over E. faecium and S. aureus. Additionally, P. aeruginosa appeared as a vast layer at the bottom of the samples, while S. aureus formed grape-like clusters. In the second model, the distribution was even clearer. Only a few E. faecium were visible, in contrast to the vast layer of P. aeruginosa. It seems that the different species avoid each other and seek their respective niches. These mixed-species biofilm models showed that efficacy and tolerance to antimicrobial substances are nearly species-independent. Their frequent application appears to be important. The bacterial wound biofilm remains a challenge in treatment and requires new, combined therapy options.

Next-Generation Diagnostic Wound Dressings for Diabetic Wounds

Chronic lower extremity wounds (diabetic foot ulcers) are a serious and prevalent complication of diabetes. These wounds exhibit low healing rates and present a high risk of amputation. Current diagnostic options for foot ulcers are limited to macroscopic wound analysis such as wound depth, implicated tissues, and infection. Molecular diagnostics promises to improve foot ulcer diagnosis, staging, and assessment of the treatment response. In this perspective, we report recent progress in understanding the pathophysiology of diabetic wound healing and point to recently emerged novel molecular targets for wound diagnostics. We discuss selected diagnostic wound dressings under preclinical development that detect one or several inflammatory markers, bacterial secretions, hyperglycemia, and mechanical stress. We also highlight key translational challenges of investigational diagnostic bandages for diabetic foot ulcers.

Adhesive-Free, Stretchable, and Permeable Multiplex Wound Care Platform

The wound healing process remains a poorly understood biological mechanism. The high morbidity and mortality rates associated with chronic wounds are a critical concern to the health care industry. Although assessments and treatment options exist, these strategies have primarily relied on static wound dressings that do not consider the dynamic physicochemical microenvironment and can often create additional complications through the frequent dressing changing procedure. Inspired by the need for engineering "smart" bandages, this study resulted in a multifaceted approach to developing an adhesive-free, permeable, and multiplex sensor system. The electronic-extracellular matrix (e-ECM) platform is capable of noninvasively monitoring chemical and physical changes in real-time on a flexible, stretchable, and permeable biointegrated platform. The multiplex sensors are constructed atop a soft, thin, and microfibrous substrate of silicone to yield a conformal, adhesive-free, convective, or diffusive wound exudate flow, and passive gas transfer for increased cellular epithelization and unobstructed physical and chemical sensor monitoring at the wound site. This platform emulates the native epidermal mechanics and physical extracellular matrix architecture for intimate bio-integration. The multiple biosensor array can continuously examine inflammatory biomarker such as lactate, glucose, pH, oxygen, and wound temperature that correlates to the wound healing status. Additionally, a heating element was incorporated to maintain the optimal thermal conditions at the wound bed. The e-ECM electrochemical biosensors were tested in vitro, within phosphate-buffered saline, and ex vivo, within wound exudate. The "smart" wound bandage combines biocompatible materials, treatments, and monitoring modalities on a microfibrous platform for complex wound dynamic control and analysis.

Wearable Sensors for the Detection of Biomarkers for Wound Infection

Infection represents a major complication that can affect wound healing in any type of wound, especially in chronic ones. There are currently certain limitations to the methods that are used for establishing a clinical diagnosis of wound infection. Thus, new, rapid and easy-to-use strategies for wound infection diagnosis need to be developed. To this aim, wearable sensors for infection diagnosis have been recently developed. These sensors are incorporated into the wound dressings that are used to treat and protect the wound, and are able to detect certain biomarkers that can be correlated with the presence of wound infection. Among these biomarkers, the most commonly used ones are pH and uric acid, but a plethora of others (lactic acid, oxygenation, inflammatory mediators, bacteria metabolites or bacteria) have also been detected using wearable sensors. In this work, an overview of the main types of wearable sensors for wound infection detection will be provided. These sensors will be divided into electrochemical, colorimetric and fluorimetric sensors and the examples will be presented and discussed comparatively.

Milieu matters: An in vitro wound milieu to recapitulate key features of, and probe new insights into, mixed-species bacterial biofilms

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro studies employ refined laboratory media to study biofilms, representing conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. With Luria-Bertani broth and Fetal Bovine Serum (FBS) for comparison, the IVWM was used to study planktonic growth, biofilm features, and interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as biomass formation, metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for monospecies and mixed-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

Lactate Is a Metabolic Mediator That Shapes Immune Cell Fate and Function

Lactate and the associated H⁺ ions are still introduced in many biochemistry and general biology textbooks and courses as a metabolic by-product within fast or oxygen-independent glycolysis. However, the role of lactate as a fuel source has been well-appreciated in the field of physiology, and the role of lactate as a metabolic feedback regulator and distinct signaling molecule is beginning to gain traction in the field of immunology. We now know that while lactate and the associated H⁺ ions are generally immunosuppressive negative regulators, there are cell, receptor, mediator, and microenvironment-specific effects that augment T helper (Th)17, macrophage (M)2, tumor-associated macrophage, and neutrophil functions. Moreover, we are beginning to uncover how lactate and H⁺ utilize different transporters and signaling cascades in various immune cell types. These immunomodulatory effects may have a substantial impact in cancer, sepsis, autoimmunity, wound healing, and other immunomodulatory conditions with elevated lactate levels. In this article, we summarize the known effects of lactate and H⁺ on immune cells to hypothesize potential explanations for the divergent inflammatory vs. anti-inflammatory effects.

Impact of microRNA-210 on wound healing among the patients with diabetic foot ulcer

Aim

Diabetic foot ulcer (DFU) is a major concern in diabetes and its control requires in-depth molecular investigation. The present study aimed to screen the expression of microRNA-210 (miR-210) and its association in hypoxic pathway in DFU patients.

Methods

The study consists of 3 groups of circulation samples (50 in each group of: healthy volunteers, T2DM and T2DM with DFU) and 2 groups of tissue samples (10 in each group of: control and T2DM with DFU). Expression of miR-210 and hypoxia inducible factor-1 alpha (HIF-1α), and its responsive genes such as VEGF, TNF-α, IL-6, BCl2, Bax and Caspase 3 were analyzed by RT-PCR, Western blot and ELISA analyses.

Results

The HIF-1α expression decreased in DFU patients with increased miR-210 expression in both circulation and tissue biopsies. The circulatory IL-6 and inflammatory gene TNF-α expression was increased in DFU compared to healthy controls and T2DM subjects. Further, we found there was no alteration in the angiogenic marker, VEGF expression. In comparison, anti-apoptotic BCl2 was decreased and Bax and Caspase 3 was increased in DFU tissues relative to control.

Conclusions

The study showed that there was an inverse relationship between miR-210 and HIF-1α expression in patients with DFU, indicating that miR-210 may regulate the expression of the hypoxic gene.

Dermal fibroblast cells interactions with single and triple bacterial-species biofilms

Polymicrobial biofilm leads to wound healing delay. We set up an in vitro co-culture model of single- and triple-species biofilms of Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis with dermal fibroblast to assess the fibroblast response against to the different biofilms. Scratch and viability assays and biofilm cell quantifications were performed by WST-1, CLSM and plating method, respectively. Quorum sensing-related gene expression levels in P. aeruginosa and E. faecalis were analysed by reverse-transcriptase PCR. The immune responses of cells against S. aureus, P. aeruginosa and E. faecalis biofilms were measured by cytokine and matrix metalloproteinase analyzes. The influence of biofilm soluble factors on fibroblasts was also determined. After 24 h, triple-species biofilm cells caused the removal of the fibroblasts from the surfaces indicating the negative synergistic effect of three species. After co-cultures, twenty-five cytokines were significantly increased in fibroblast cells compared to control. Compared to other strains, the most important cytokine, chemokine and growth factors increased was observed in P. aeruginosa co-cultures with fibroblast. While the expressions of fsrB and gelE genes were significantly upregulated in E. faecalis biofilm cells cultured with fibroblast cells, no significant difference was observed in P. aeruginosa. The wound healing and cell growth of fibroblasts were disrupted more aggressively in the presence of P. aeruginosa and triple-species biofilm cells. P. aeruginosa generally induced a stronger immune response in the fibroblasts than E. faecalis and S. aureus.

Macrophage mediation in normal and diabetic wound healing responses

PURPOSE

The failure in timely healing of wounds is a central feature in chronic wounds that leads to physiological, psychological and economic burdens. Macrophages have been demonstrated to have various functions in wounds including host defense, the promotion and resolution of inflammation, the removal of apoptotic cells and tissue restoration following injury. Accumulated evidence suggests that macrophage dysfunction is a component of the pathogenesis of non-healing wounds. While the overall signaling cascades have been well understood, their complex interplay and a detailed characterization of events that are disrupted in chronic wounds have still not emerged satisfactorily.

METHODS

The existing literature was reviewed to summarize the regulation of macrophage polarization in wound closure and dysregulation in non-healing wounds. Further, the review also underscored the role of Nrf2 in promoting macrophage-mediated regulation in wound responses and in particular, macrophage involvement in iron homeostasis that is impaired in chronic wounds such as in diabetes.

RESULTS

The mechanisms involved in the reprogramming of macrophage subtypes in chronic wounds are still emerging. Furthermore, treating non-healing wounds has increasingly been shifting focus from generic treatments to the development of targeted therapies. Increasing evidence suggests the need for modeling wound tissue in vitro which may very well serve a critical aspect to characterize the relevant factors that sustain chronic wounds in vivo such as the constant iron overload at the wound site from recurrent infection and bleeding.

CONCLUSION

The development of targeted therapies and also developing a reliable means to monitor assisted healing of chronic wounds are two major goals to be pursued. In addition, identifying molecular targets that can regulate macrophages to aid tissue restoration in chronic wounds would serve the crucial step in realizing both aforementioned goals.

Diagnosis of infection in the foot in diabetes: a systematic review

BACKGROUND

Securing an early accurate diagnosis of diabetic foot infections and assessment of their severity are of paramount importance since these infections can cause great morbidity and potentially mortality and present formidable challenges in surgical and antimicrobial treatment.

METHODS

In June 2018, we searched the literature using PuEbMed and EMBASE for published studies on the diagnosis of diabetic foot infection. On the basis of predetermined criteria, we reviewed prospective controlled, as well as noncontrolled, studies in any language, seeking translations for those not in English. We then developed evidence statements on the basis of the included papers.

RESULTS

From the 4242 records screened, we selected 35 papers that met our inclusion criteria. The quality of all but one of the evidence statements was low because of the weak methodology of nearly all of the studies. The available data suggest that diagnosing diabetic foot infections on the basis of clinical signs and symptoms and classified according to the International Working Group of the Diabetic Foot scheme correlates with the patient's likelihood of ulcer healing, of lower extremity amputation, and risk of death. Elevated levels of selected serum inflammatory markers are supportive, but not diagnostic, of soft tissue or bone infection. In patients with suspected diabetic foot osteomyelitis, both a positive probe-to-bone test and an elevated erythrocyte sedimentation rate are strongly associated with its presence. Culturing tissue samples of soft tissues or bone, when care is taken to avoid contamination, provides more accurate microbiological information than culturing superficial (swab) samples. Plain X-ray remains the first-line imaging examination when there is suspicion of diabetic foot osteomyelitis, but advanced imaging methods help in cases when either the diagnosis or the localization of infection is uncertain.

CONCLUSION

The results of this first reported systematic review on the diagnosis of diabetic foot infections provide some guidance for clinicians, but there is a need for more prospective controlled studies of high quality.

Lactic Acid Inhibits Lipopolysaccharide-Induced Mast Cell Function by Limiting Glycolysis and ATP Availability

Sepsis has a well-studied inflammatory phase, with a less-understood secondary immunosuppressive phase. Elevated blood lactate and slow lactate clearance are associated with mortality; however, regulatory roles are unknown. We hypothesized that lactic acid (LA) contributes to the late phase and is not solely a consequence of bacterial infection. No studies have examined LA effects in sepsis models in vivo or a mechanism by which it suppresses LPS-induced activation in vitro. Because mast cells can be activated systemically and contribute to sepsis, we examined LA effects on the mast cell response to LPS. LA significantly suppressed LPS-induced cytokine production and NF-κB transcriptional activity in mouse bone marrow-derived mast cells and cytokine production in peritoneal mast cells. Suppression was MCT-1 dependent and reproducible with sodium lactate or formic acid. Further, LA significantly suppressed cytokine induction following LPS-induced endotoxemia in mice. Because glycolysis is linked to inflammation and LA is a byproduct of this process, we examined changes in glucose metabolism. LA treatment reduced glucose uptake and lactate export during LPS stimulation. LA effects were mimicked by glycolytic inhibitors and reversed by increasing ATP availability. These results indicate that glycolytic suppression and ATP production are necessary and sufficient for LA effects. Our work suggests that enhancing glycolysis and ATP production could improve immune function, counteracting LA suppressive effects in the immunosuppressive phase of sepsis.

Inhibiting Glycolysis and ATP Production Attenuates IL-33-Mediated Mast Cell Function and Peritonitis

Cellular metabolism and energy sensing pathways are closely linked to inflammation, but there is little understanding of how these pathways affect mast cell function. Mast cells are major effectors of allergy and asthma, and can be activated by the alarmin IL-33, which is linked to allergic disease. Therefore, we investigated the metabolic requirements for IL-33-induced mast cell function, to identify targets for controlling inflammation. We found that IL-33 increases glycolysis, glycolytic protein expression, and oxidative phosphorylation (OX PHOS). Inhibiting OX PHOS had little effect on cytokine production, but antagonizing glycolysis with 2-deoxyglucose or oxamate suppressed inflammatory cytokine production in vitro and in vivo. ATP reversed this suppression. Glycolytic blockade suppressed IL-33 signaling, including ERK phosphorylation, NFκB transcription, and ROS production in vitro, and suppressed IL-33-induced neutrophil recruitment in vivo. To test a clinically relevant way to modulate these pathways, we examined the effects of the FDA-approved drug metformin on IL-33 activation. Metformin activates AMPK, which suppresses glycolysis in immune cells. We found that metformin suppressed cytokine production in vitro and in vivo, effects that were reversed by ATP, mimicking the actions of the glycolytic inhibitors we tested. These data suggest that glycolytic ATP production is important for IL-33-induced mast cell activation, and that targeting this pathway may be useful in allergic disease.

Levels of wound calprotectin and other inflammatory biomarkers aid in deciding which patients with a diabetic foot ulcer need antibiotic therapy (INDUCE study)

AIMS

Deciding if a diabetic foot ulcer is infected in a community setting is challenging without validated point-of-care tests. Four inflammatory biomarkers were investigated to develop a composite algorithm for mildly infected diabetic foot ulcers: venous white cell count, C-reactive protein (CRP) and procalcitonin, and a novel wound exudate calprotectin assay. Calprotectin is a marker of neutrophilic inflammation.

METHODS

In a prospective study, people with uninfected or mildly infected diabetic foot ulcers who had not received oral antibiotics in the preceding 2 weeks were recruited from community podiatry clinics for measurement of inflammatory biomarkers. Antibiotic prescribing decisions were based on clinicians' baseline assessments and participants were reviewed 1 week later; ulcer infection was defined by clinicians' overall impression from their two assessments.

RESULTS

Some 363 potential participants were screened, of whom 67 were recruited, 29 with mildly infected diabetic foot ulcers and 38 with no infection. One participant withdrew early in each group. Ulcer area was 1.32 cm² [interquartile range (IQR) 0.32-3.61 cm² ] in infected ulcers and 0.22 cm² (IQR 0.09-1.46 cm² ) in uninfected ulcers. Baseline CRP for mild infection was 9.00 mg/ml and 6.00 mg/ml for uninfected ulcers; most procalcitonin levels were undetectable. Median calprotectin level in infected diabetic foot ulcers was 1437 ng/ml and 879 ng/ml in uninfected diabetic foot ulcers. Area under the receiver operating characteristic curve for a composite algorithm incorporating calprotectin, CRP, white cell count and ulcer area was 0.68 (95% confidence intervals 0.52-0.82), sensitivity 0.64, specificity 0.81.

CONCLUSIONS

A composite algorithm including CRP, calprotectin, white cell count and ulcer area may help to distinguish uninfected from mildly infected diabetic foot ulcers. Venous procalcitonin is unhelpful for mild diabetic foot ulcer infection.

The effect of pH on cell viability, cell migration, cell proliferation, wound closure, and wound reepithelialization: In vitro and in vivo study

Wound microenvironment plays a major role in the process of wound healing. It contains various external and internal factors that participate in wound pathophysiology. The pH is an important factor that influences wound healing by changing throughout the healing process. Several previous studies have investigated the role of pH in relation to pathogens but studies concentrating on the effects of pH on wound healing itself are inconclusive. The purpose of this study was to comprehensively and in a controlled fashion investigate the effect of pH on wound healing by studying its effect on human primary keratinocyte and fibroblast function in vitro and on wound healing in vivo. In vitro, primary human keratinocytes and fibroblasts were cultured in different levels of pH (5.5-12.5) and the effect on cell viability, proliferation, and migration was studied. A rat full-thickness wound model was used to investigate the effect of pH (5.5-9.5) on wound healing in vivo. The effect of pH on inflammation was monitored by measuring IL-1 α concentrations from wounds and cell cultures exposed to different pH environments. Our results showed that both skin cell types tolerated wide range of pH very well. They further demonstrated that both acidic and alkaline environments decelerated cell migration in comparison to neutral environments and interestingly alkaline conditions significantly enhanced cell proliferation. Results from the in vivo experiments indicated that a prolonged, strongly acidic wound environment prevents both wound closure and reepithelialization while a prolonged alkaline environment did not have any negative impact on wound closure or reepithelialization. Separately, both in vitro and in vivo studies showed that prolonged acidic conditions significantly increased the expression of IL-1 α in fibroblast cultures and in wound fluid, whereas prolonged alkaline conditions did not result in elevated amounts of IL-1 α.

Microenvironment and microbiology of skin wounds: the role of bacterial biofilms and related factors

Wound healing is a systemic response to injury that impacts the entire body and not just the site of tissue damage; it represents one of the most complex biological processes. Our knowledge of wound healing continues to evolve and it is now clear that the wound microenvironment plays a crucial role. The interactions between cells and the surface microenvironment, referred to as the "biofilm," contributes to skin homeostasis and healing. Understanding the functional complexity of the wound microenvironment informs how various factors such as age, ischemia, or bacterial infections can impair or arrest the normal healing processes, and it also allows for the possibility of acting therapeutically on healing defects with microenvironment manipulation. Microbes represent a particularly important factor for influencing the wound microenvironment and therefore wound healing. Moreover, the role of infections, particularly those that are sustained by biofilm-forming bacteria, is mutually related to other microenvironment aspects, such as humidity, pH, metalloproteinases, and reactive oxygen species, on which the modern research of new therapeutic strategies is focused. Today, chronic wounds are a rapidly growing health care burden and it is progressively understood that many non-healing wounds might benefit from therapies that target microorganisms and their biofilm communities. There is no doubt that host factors like perfusion impairments, venous insufficiency, pressure issues, malnutrition, and comorbidities strongly impact the healing processes and therefore must be targeted in the therapeutic management, but this approach might be not enough. In this article, we detail how bacterial biofilms and related factors impair wound healing, the reasons they must be considered a treatment target that is as important as the host's local and systemic pathologic conditions, and the latest therapeutic strategies derived from the comprehension of the wound microenvironment.

The external microenvironment of healing skin wounds

The skin wound microenvironment can be divided into two main components that influence healing: the external wound microenvironment, which is outside the wound surface; and the internal wound microenvironment, underneath the surface, to which the cells within the wound are exposed. Treatment methods that directly alter the features of the external wound microenvironment indirectly affect the internal wound microenvironment due to the exchange between the two compartments. In this review, we focus on the effects of temperature, pressure (positive and negative), hydration, gases (oxygen and carbon dioxide), pH, and anti-microbial treatment on the wound. These factors are well described in the literature and can be modified with treatment methods available in the clinic. Understanding the roles of these factors in wound pathophysiology is of central importance in wound treatment.

microRNA and Wound Healing

microRNAs (miRNAs) are small noncoding RNA molecules which play pivotal roles in wound healing. The increased expression of certain genes and expression of some others represent a key component of the wound biology and are largely under the regulation of naturally occurring miRNAs. Understanding the dysregulated miRNAs in chronic wound biology will therefore enable the development of newer therapies. This chapter focuses on the miRNAs that can be potentially targeted for improving skin wound healing and the challenges in miRNA therapy, including considerations in miRNA target identification and delivery.

Fatal skin and soft tissue infection of multidrug resistant Acinetobacter baumannii: A case report

INTRODUCTION

Acinetobacter baumannii is usually associated with respiratory tract, urinary tract and bloodstream infections. Recent reports suggest that it is increasingly causing skin and soft tissue infections. It is also evolving as a multidrug resistant organism that can be difficult to treat. We present a fatal case of multidrug resistant A. baumannii soft tissue infection and review of relevant literature.

PRESENTATION OF CASE

A 41 year old morbidly obese man, with history of alcoholic liver disease presented with left superficial pre-tibial abrasions and cellulitis caused by multidrug resistant (MDR) A. baumannii. In spite of early antibiotic administration he developed extensive myositis and fat necrosis requiring extensive and multiple surgical debridements. He deteriorated despite appropriate antibiotic therapy and multiple surgical interventions with development of multi-organ failure and died.

DISCUSSION

Managing Acinetobacter infections remains difficult due to the array of resistance and the pathogens ability to develop new and ongoing resistance. The early diagnosis of necrotizing soft tissue infection may be challenging, but the key to successful management of patients with necrotizing soft tissue infection are early recognition and complete surgical debridement.

CONCLUSION

A. baumannii is emerging as an important cause of severe, life-threatening soft tissue infections. Multidrug resistant A. baumannii soft tissue infections may carry a high mortality in spite of early and aggressive treatment. Clinicians need to consider appropriate early empirical antibiotic coverage or the use of combination therapy to include MDR A. baumannii as a cause of skin and soft tissue infections.

Wound Fluid in Diabetic Foot Ulceration

Valid and reproducible sampling techniques as well as processing protocols are required for the assessment of biomarkers and mediators contained in wound exudate. Moreover, the ideal technique should be easy to use even in daily clinical routine. This is challenging since wound fluid represents an inhomogeneous mixture of different exogenous and endogenous sources. Analyzing wound fluid, however, may facilitate clinical decision making. Many techniques for obtaining wound fluid have been described. There is very little validation data, and the array of different techniques appears confusing. Structuring and new standards are needed to avoid wound fluid sampling yielding an “undefined soup.” A lot of wound fluid parameters have been analyzed, although none of them have made its way into clinical practice. Nevertheless, basic principles of wound healing have been established from wound fluid analysis. With adequate techniques suitable for daily practice, basic research might foster our clinical understanding of wound healing with implications for new therapies. So far, research has mainly concentrated on analyzing available sample material with respect to either a wide variety of analytes or comparing acute with chronic wound exudate. Clinical endpoints such as healing or wound infection as well as longitudinal data may indeed be more valuable for clinical practice, enabling the discovery of meaningful biomarkers using a suitable technique.

Lactate influences the gene expression profile of human mesenchymal stem cells (hMSC) in a dose dependant manner

BACKGROUND/AIMS

Wounds, especially non-healing wounds are characterized by elevated tissue lactate concentrations. Lactate is known for being able to stimulate collagen synthesis and vessel growth. Lately it has been shown that lactate, in vivo, plays an important role in homing of stem cells. With this work we aimed to show the influence of lactate on the gene expressionprofile of human mesenchymal stem cells (hMSC).

MATERIALS AND METHODS

hMSCs were obtained from bone marrow and characterized with fluorescence-activated cell sorting (FACS) analysis. Subsequently the hMSCs were treated with either 0, 5, 10 and 15 mM lactate (pH 7,4) for 24 hours. RNA Isolation from stimulated hMSCs and controls was performed. The Microarray analysis was performed using AffymetrixHuGene 1.0 ST Gene Chip. Selected targets were subsequently analysed using quantitative real time PCR (RTq-PCR).

RESULTS

We were able to show that lactate in moderate concentrations of 5 respectively 10 mM leads to an anti-inflammatory, anti-apoptotic but growth and proliferation promoting gene expression after 24 h. In contrast, high lactate concentrations of 15 mM leads to the opposed effect, namely promoting inflammation and apoptosis. Hypoxia induced genes did not show any significant regulation. Contrary to expectation, we were not able to show any significant regulation of candidates associated with glycolysis.

CONCLUSION

We were able to show that lactate alters gene expression but does not change the cell phenotype, which might be helpful for further investigations of new treatment strategies for chronic non-healing wounds as well as tumor-therapy and neuronal plasticity.

Superficial wound swabbing: a novel method of sampling and processing wound fluid for subsequent immunoassay analysis in diabetic foot ulcerations

OBJECTIVE

In diabetic foot ulcers, wound fluid inflammatory mediators have previously been proposed as surrogate markers for nonhealing. However, currently available wound fluid sampling techniques are not suitable for clinical practice due to low levels of exudate and a high logistical effort. The aim of this investigation was to assess 1) the technique of superficial wound swabbing for harvesting wound fluid; and 2) the quality of the collected fluid for immunoassay analysis of inflammatory mediators.

RESEARCH DESIGN AND METHODS

Both nylon-flocked swabs and film dressings were used to collect wound fluid from foot ulcers of diabetic patients. In randomly selected patients, levels of wound fluid inflammatory mediators and matrix metalloproteases were determined using multiplexed bead-based sandwich immunoassays with respect to both sampling methods. Wound fluid spike-in experiments were performed to evaluate the impact of different sample processing protocols on subsequent immunoassay analysis.

RESULTS

Using the swabbing technique, a median amount of 40 µL (2-120 µL) wound exudate was collected, which allowed the measurement of several multiplex panels. Comparing both sampling methods, a similar qualitative protein recovery was observed with a trend to analyte enrichment by swabbing. Sample processing using swabs did not affect analyte recovery, with the exception of interleukin (IL)-8, thymus and activation-regulated chemokine, IL-17A, interferon-γ-induced protein 10, and IL-4.

CONCLUSIONS

The quality of wound fluid collected by superficial swabbing is not inferior to the current standard technique. Combined with subsequent bead-based sandwich immunoassay analysis, this new method offers a noninvasive technique, suitable for daily clinical routines, for assessment of inflammatory activity in diabetic foot ulcers.

The lactate conundrum in wound healing: clinical and experimental findings indicate the requirement for a rapid point-of-care diagnostic

The increasing prevalence of chronic wounds has significant financial implications for nations with advanced healthcare provision. Although the diseases that predispose to hard-to-heal wounds are recognized, their etiology is less well understood, partly because practitioners in wound management lack specialized diagnostic support. Prognostic indicators for healing may be inherent to wound biochemistry but remain invisible under routine clinical investigation; lactate is an example of this. In this study, lactate concentration in exudate obtained from 20 patients undergoing wound management in hospital was variable but in some cases approached or exceeded 20 mM. In vitro viability studies indicated that fibroblasts and endothelial cells tolerated low levels of lactate (1-10 mM), but cell viability was severely compromised by high lactate concentrations (=20 mM). Scratched monolayer experiments revealed that cell migration was affected earlier than viability in response to increasing lactate dose, and this was shown by immunocytochemistry to be associated with cytoskeletal disruption. A prototype enzyme-based colorimetric assay for lactate generating a color change that was rapid in the context of clinical practise, and capable of functioning within a gel vehicle, was developed with point-of-care dipstick applications in mind. A randomized single-blinded trial involving 30 volunteers and using a color chart to calibrate the assay demonstrated that lactate concentration could be reliably estimated with 5 mM precision; this suggesting that "physiological" and "pathological" lactate concentration could be distinguished. The present data suggest that a dipstick-type colorimetric assay could comprise a viable diagnostic tool for identifying patients at-risk from high-wound lactate.