Microbiota of Chronic Diabetic Wounds: Ecology, Impact, and Potential for Innovative Treatment Strategies

Understanding and treating diabetic foot ulcers: Insights into the role of cutaneous microbiota and innovative therapies

Background

Notoriously known as the silent pandemic, chronic, non-healing diabetic foot ulcers (DFUs), pose a significant rate of incidence for amputation and are a major cause of morbidity. Alarmingly, the treatment and management strategies of chronic wounds represent a significant economic and health burden as well as a momentous drain on resources with billions per annum being spent in the US and UK alone. Defective wound healing is a major pathophysiological condition which propagates an acute wound to a chronic wound, further propelled by underlying conditions such as diabetes and vascular complications which are more prevalent amongst the elderly. Chronic wounds are prone to infection, which can exacerbate the condition, occasionally resulting in amputation for the patient, despite the intervention of modern therapies. However, amputation can only yield a 5-year survival rate for 50% of patients, highlighting the need for new treatments for chronic wounds.

Findings

The dynamic cutaneous microbiota is comprised of diverse microorganisms that often aid wound healing. Conversely, the chronic wound microbiome consists of a combination of common skin commensals such as Staphylococcus aureus and Staphylococcus epidermidis, as well as the opportunistic pathogen Pseudomonas aeruginosa. These bacteria have been identified as the most prevalent bacterial pathogens isolated from chronic wounds and contribute to prolific biofilm formation decreasing the efficiency of antimicrobials and further perpetuating a hyper-inflammatory state.

Discussion and Conclusion

Here, we review recent advances and provide a new perspective on alternative treatments including phage and microbiome transplant therapies and how the definitive role of the cutaneous microbiota impacts the aetiology of DFUs.

Microbiological profile of diabetic foot infections in China and worldwide: a 20-year systematic review

Introduction

Pathogens causing diabetic foot infections (DFIs) vary by region globally; however, knowledge of the causative organism is essential for effective empirical treatment. We aimed to determine the incidence and antibiotic susceptibility of DFI pathogens worldwide, focusing on Asia and China.

Methods

Through a comprehensive literature search, we identified published studies on organisms isolated from DFI wounds from January 2000 to December 2020.

Results

Based on our inclusion criteria, we analyzed 245 studies that cumulatively reported 38,744 patients and 41,427 isolated microorganisms. DFI pathogens varied according to time and region. Over time, the incidence of Gram-positive and Gram-negative aerobic bacteria have decreased and increased, respectively. America and Asia have the highest (62.74%) and lowest (44.82%) incidence of Gram-negative bacteria, respectively. Africa has the highest incidence (26.90%) of methicillin-resistant Staphylococcus aureus. Asia has the highest incidence (49.36%) of Gram-negative aerobic bacteria with species infection rates as follows: Escherichia coli, 10.77%; Enterobacter spp., 3.95%; and Pseudomonas aeruginosa, 11.08%, with higher local rates in China and Southeast Asia. Linezolid, vancomycin, and teicoplanin were the most active agents against Gram-positive aerobes, while imipenem and cefoperazone-sulbactam were the most active agents against Gram-negative aerobes.

Discussion

This systematic review showed that over 20 years, the pathogens causing DFIs varied considerably over time and region. This data may inform local clinical guidelines on empirical antibiotic therapy for DFI in China and globally. Regular large-scale epidemiological studies are necessary to identify trends in DFI pathogenic bacteria.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023447645.

A Multidisciplinary Approach to End-Stage Limb Salvage in the Highly Comorbid Atraumatic Population: An Observational Study

Background: The use of free tissue transfer (FTT) is efficacious for chronic, non-healing lower extremity (LE) wounds. The four pillars of managing patient comorbidities, infection control, blood flow status, and biomechanical function are critical in achieving successful limb salvage. The authors present their multidisciplinary institutional experience with a review of 300 FTTs performed for the complex LE limb salvage of chronic LE wounds. Methods: A single-institution, retrospective review of atraumatic LE FTTs performed by a single surgeon from July 2011 to January 2023 was reviewed. Data on patient demographics, comorbidities, preoperative management, intraoperative details, flap outcomes, postoperative complications, and long-term outcomes were collected. Results: A total of 300 patients who underwent LE FTT were included in our retrospective review. Patients were on average 55.9 ± 13.6 years old with a median Charlson Comorbidity Index of 4 (IQR: 3). The majority of patients were male (70.7%). The overall hospital length of stay (LOS) was 27 days (IQR: 16), with a postoperative LOS of 14 days (IQR: 9.5). The most prevalent comorbidities were diabetes (54.7%), followed by peripheral vascular disease (PVD: 35%) and chronic kidney disease (CKD: 15.7%). The average operative LE FTT time was 416 ± 115 min. The majority of flaps were anterolateral thigh (ALT) flaps (52.7%), followed by vastus lateralis (VL) flaps (25.3%). The immediate flap success rate was 96.3%. The postoperative ipsilateral amputation rate was 12.7%. Conclusions: Successful limb salvage is possible in a highly comorbid patient population with a high prevalence of diabetes mellitus, peripheral vascular disease, and end-stage renal disease. In order to optimize patients prior to their LE FTT, extensive laboratory, arterial, and venous preoperative testing and diabetes management are needed preoperatively. Postoperative monitoring and long-term follow-up with a multidisciplinary team are also crucial for long-term limb salvage success.

Narrative review on nanoparticles based on current evidence: therapeutic agents for diabetic foot infection

Diabetes's effects on wound healing present a major treatment challenge and increase the risk of amputation. When traditional therapies fail, new approaches must be investigated. With their submicron size and improved cellular internalisation, nanoparticles present a viable way to improve diabetic wound healing. They are attractive options because of their innate antibacterial qualities, biocompatibility, and biodegradability. Nanoparticles loaded with organic or inorganic compounds, or embedded in biomimetic matrices such as hydrogels, chitosan, and hyaluronic acid, exhibit excellent anti-inflammatory, antibacterial, and antioxidant properties. Drug delivery systems (DDSs)-more precisely, nanodrug delivery systems (NDDSs)-use the advantages of nanotechnology to get around some of the drawbacks of traditional DDSs. Recent developments show how expertly designed nanocarriers can carry a variety of chemicals, transforming the treatment of diabetic wounds. Biomaterials that deliver customised medications to the wound microenvironment demonstrate potential. Delivery techniques for nanomedicines become more potent than ever, overcoming conventional constraints. Therapeutics for diabetes-induced non-healing wounds are entering a revolutionary era thanks to precisely calibrated nanocarriers that effectively distribute chemicals. This review highlights the therapeutic potential of nanoparticles and outlines the multifunctional nanoparticles of the future that will be used for complete wound healing in diabetics. The investigation of novel nanodrug delivery systems has the potential to revolutionise diabetic wound therapy and provide hope for more efficient and focused therapeutic approaches.

Triple threat: how diabetes results in worsened bacterial infections

Diabetes mellitus, characterized by impaired insulin signaling, is associated with increased incidence and severity of infections. Various diabetes-related complications contribute to exacerbated bacterial infections, including hyperglycemia, innate immune cell dysfunction, and infection with antibiotic-resistant bacterial strains. One defining symptom of diabetes is hyperglycemia, resulting in elevated blood and tissue glucose concentrations. Glucose is the preferred carbon source of several bacterial pathogens, and hyperglycemia escalates bacterial growth and virulence. Hyperglycemia promotes specific mechanisms of bacterial virulence known to contribute to infection chronicity, including tissue adherence and biofilm formation. Foot infections are a significant source of morbidity in individuals with diabetes and consist of biofilm-associated polymicrobial communities. Bacteria perform complex interspecies behaviors conducive to their growth and virulence within biofilms, including metabolic cross-feeding and altered phenotypes more tolerant to antibiotic therapeutics. Moreover, the metabolic dysfunction caused by diabetes compromises immune cell function, resulting in immune suppression. Impaired insulin signaling induces aberrations in phagocytic cells, which are crucial mediators for controlling and resolving bacterial infections. These aberrancies encompass altered cytokine profiles, the migratory and chemotactic mechanisms of neutrophils, and the metabolic reprogramming required for the oxidative burst and subsequent generation of bactericidal free radicals. Furthermore, the immune suppression caused by diabetes and the polymicrobial nature of the diabetic infection microenvironment may promote the emergence of novel strains of multidrug-resistant bacterial pathogens. This review focuses on the "triple threat" linked to worsened bacterial infections in individuals with diabetes: (i) altered nutritional availability in diabetic tissues, (ii) diabetes-associated immune suppression, and (iii) antibiotic treatment failure.

The Use of Photoactive Polymeric Nanoparticles and Nanofibers to Generate a Photodynamic-Mediated Antimicrobial Effect, with a Special Emphasis on Chronic Wounds

This review is concerned with chronic wounds, with an emphasis on biofilm and its complicated management process. The basics of antimicrobial photodynamic therapy (PDT) and its underlying mechanisms for microbial eradication are presented. Intrinsically active nanocarriers (polydopamine NPs, chitosan NPs, and polymeric micelles) that can further potentiate the antimicrobial photodynamic effect are discussed. This review also delves into the role of photoactive electrospun nanofibers, either in their eluting or non-eluting mode of action, in microbial eradication and accelerating the healing of wounds. Synergic strategies to augment the PDT-mediated effect of photoactive nanofibers are reviewed.

Clinical practice recommendations for infectious disease management of diabetic foot infection (DFI) - 2023 SPILF

In march 2020, the International Working Group on the Diabetic Foot (IWGDF) published an update of the 2015 guidelines on the diagnosis and management of diabetic foot infection (DFI). While we (the French ID society, SPILF) endorsed some of these recommendations, we wanted to update our own 2006 guidelines and specifically provide informative elements on modalities of microbiological diagnosis and antibiotic treatment (especially first- and second-line regiments, oral switch and duration). The recommendations put forward in the present guidelines are addressed to healthcare professionals managing patients with DFI and more specifically focused on infectious disease management of this type of infection, which clearly needs a multidisciplinary approach. Staging of the severity of the infection is mandatory using the classification drawn up by the IWGDF. Microbiological samples should be taken only in the event of clinical signs suggesting infection in accordance with a strict preliminarily established protocol. Empirical antibiotic therapy should be chosen according to the IWGDF grade of infection and duration of the wound, but must always cover methicillin-sensitive Staphylococcus aureus. Early reevaluation of the patient is a fundamental step, and duration of antibiotic therapy can be shortened in many situations. When osteomyelitis is suspected, standard foot radiograph is the first-line imagery examination and a bone biopsy should be performed for microbiological documentation. Histological analysis of the bone sample is no longer recommended. High dosages of antibiotics are recommended in cases of confirmed osteomyelitis.

Emerging Multiscale Biofabrication Approaches for Bacteriotherapy

Bacteriotherapy is emerging as a strategic and effective approach to treat infections by providing putatively harmless bacteria (i.e., probiotics) as antagonists to pathogens. Proper delivery of probiotics or their metabolites (i.e., post-biotics) can facilitate their availing of biomaterial encapsulation via innovative manufacturing technologies. This review paper aims to provide the most recent biomaterial-assisted strategies proposed to treat infections or dysbiosis using bacteriotherapy. We revised the encapsulation processes across multiscale biomaterial approaches, which could be ideal for targeting different tissues and suit diverse therapeutic opportunities. Hydrogels, and specifically polysaccharides, are the focus of this review, as they have been reported to better sustain the vitality of the live cells incorporated. Specifically, the approaches used for fabricating hydrogel-based devices with increasing dimensionality (D)-namely, 0D (i.e., particles), 1D (i.e., fibers), 2D (i.e., fiber meshes), and 3D (i.e., scaffolds)-endowed with probiotics, were detailed by describing their advantages and challenges, along with a future overlook in the field. Electrospinning, electrospray, and 3D bioprinting were investigated as new biofabrication methods for probiotic encapsulation within multidimensional matrices. Finally, examples of biomaterial-based systems for cell and possibly post-biotic release were reported.

Gram-Negative Bacteria and Lipopolysaccharides as Risk Factors for the Occurrence of Diabetic Foot

CONTEXT

Imbalance of the skin microbial community could impair skin immune homeostasis and thus trigger skin lesions. Dysbiosis of skin microbiome may be involved in the early pathogenesis of diabetic foot (DF). However, the potential mechanism remains unclear.

OBJECTIVE

To investigate the dynamic composition and function of the foot skin microbiome with risk stratification for DF and assess whether dysbiosis of the skin microbiome induces diabetic skin lesions.

METHODS

We enrolled 90 consecutive subjects who were divided into 5 groups based on DF risk stratification: very low, low, moderate, and high risk for ulcers and a healthy control group. Integrated analysis of 16S ribosomal RNA and metagenomic sequencing of cotton swab samples was applied to identify the foot skin microbiome composition and functions in subjects. Then a mouse model of microbiota transplantation was used to evaluate the effects of the skin microbiome on diabetic skin lesions.

RESULTS

The results demonstrated that, with the progression of diabetic complications, the proportion of gram-negative bacteria in plantar skin increased. At the species level, metagenome sequencing analyses showed Moraxella osloensis to be a representative core strain in the high-risk group. The major microbial metabolites affecting diabetic skin lesions were increased amino acid metabolites, and antibiotic resistance genes in microorganisms were abundant. Skin microbiota from high-risk patients induced more inflammatory cell infiltration, similar to the lipopolysaccharide (LPS)-stimulated response, which was inhibited by Toll-like receptor 4 (TLR4) antagonists.

CONCLUSIONS

The skin microbiome in patients with diabetes undergoes dynamic changes at taxonomic and functional levels with the progression of diabetic complications. The increase in gram-negative bacteria on the skin surface through LPS-TLR4 signal transduction could induce inflammatory response in early diabetic skin lesions.

Multi-Instrumental Analysis Toward Exploring the Diabetic Foot Infection Microbiota

The polymicrobial nature of diabetic foot infection (DFI) makes accurate identification of the DFI microbiota, including rapid detection of drug resistance, challenging. Therefore, the main objective of this study was to apply matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI TOF MS) technique accompanied by multiply culture conditions to determine the microbial patterns of DFIs, as well as to assess the occurrence of drug resistance among Gram-negative bacterial isolates considered a significant cause of the multidrug resistance spread. Furthermore, the results were compared with those obtained using molecular techniques (16S rDNA sequencing, multiplex PCR targeting drug resistance genes) and conventional antibiotic resistance detection methods (Etest strips). The applied MALDI-based method revealed that, by far, most of the infections were polymicrobial (97%) and involved many Gram-positive and -negative bacterial species-19 genera and 16 families in total, mostly Enterobacteriaceae (24.3%), Staphylococcaceae (20.7%), and Enterococcaceae (19.8%). MALDI drug-resistance assay was characterized by higher rate of extended-spectrum beta-lactamases (ESBLs) and carbapenemases producers compared to the reference methods (respectively 31% and 10% compared to 21% and 2%) and revealed that both the incidence of drug resistance and the species composition of DFI were dependent on the antibiotic therapy used. MALDI approach included antibiotic resistance assay and multiply culture conditions provides microbial identification at the level of DNA sequencing, allow isolation of both common (eg. Enterococcus faecalis) and rare (such as Myroides odoratimimus) bacterial species, and is effective in detecting antibiotic-resistance, especially those of particular interest-ESBLs and carbapenemases.

Human skin bacterial microbiota homeostasis: A delicate balance between health and disease

As the largest organ of the body, the skin acts as a barrier to prevent diseases and harbors a variety of beneficial bacteria. Furthermore, the skin bacterial microbiota plays a vital role in health and disease. Disruption of the barrier or an imbalance between symbionts and pathogens can lead to skin disorders or even systemic diseases. In this review, we first provide an overview of research on skin bacterial microbiota and human health, including the composition of skin bacteria in a healthy state, as well as skin bacterial microbiota educating the immune system and preventing the invasion of pathogens. We then discuss the diseases that result from skin microbial dysbiosis, including atopic dermatitis, common acne, chronic wounds, psoriasis, viral transmission, cutaneous lupus, cutaneous lymphoma, and hidradenitis suppurativa. Finally, we highlight the progress that utilizes skin microorganisms for disease therapeutics, such as bacteriotherapy and skin microbiome transplantation. A deeper knowledge of the interaction between human health and disease and the homeostasis of the skin bacterial microbiota will lead to new insights and strategies for exploiting skin bacteria as a novel therapeutic target.

Molecular Characteristics of Staphylococcus aureus Strains Isolated from Nasal Cavity and Wound Infections Among Diabetic Patients

Staphylococcus aureus is the most common pathogen contributing to diabetic foot infections (DFI). Nasal transmission of S. aureus potentially increases the risk of endogenous infection. The aim of this study was to determine the genetic diversity and antibiotic resistance profile of S. aureus isolates in nasal and wound samples from diabetic patients. A cross-sectional study was conducted from July 2018 to September 2019. S. aureus was isolated from the anterior nares and wounds of diabetic patients. All S. aureus isolates were characterized by detection of resistance and virulence genes (mecA, ermA, ermC, hla, hlb, hlg, sea, lukDE, pvl), staphylococcal cassette chromosome mec (SCCmec)-typing and staphylococcal protein A (spa)-typing. A total of 34 S. aureus were isolated from the wounds of 115 diabetic patients with DFI. Twenty-four S. aureus isolates were collected from the anterior nares of patients, and thirteen patients had concurrent S. aureus in nasal and wound specimens. The prevalence of methicillin-resistant S. aureus (MRSA) in nasal specimens was noticeable (41.7%), and the most common spa-type in nasal and wound specimens was t14870. Nearly half of the patients with concurrent S. aureus in wound and nasal specimens had similar isolates from both sites. Our data suggest that detection and screening of S. aureus colonization in the nasal cavity may prevent subsequent endogenous infections, particularly with MRSA strains.

Colonizing microbiota is associated with clinical outcomes in diabetic wound healing

With the development of society and the improvement of life quality, more than 500 million people are affected by diabetes. More than 10 % of people with diabetes will suffer from diabetic wounds, and 80 % of diabetic wounds will reoccur, so the development of new diabetic wound treatments is of great importance. The development of skin microbe research technology has gradually drawn people's attention to the complex relationship between microbes and diabetic wounds. Many studies have shown that skin microbes are associated with the outcome of diabetic wounds and can even be used as one of the indicators of wound prognosis. Skin microbes have also been found to have the potential to treat diabetic wounds. The wound colonization of different bacteria can exert opposing therapeutic effects. It is necessary to fully understand the skin microbes in diabetic wounds, which can provide valuable guidance for clinical diabetic wound treatment.

Increased Population of CD40+ Fibroblasts Is Associated with Impaired Wound Healing and Chronic Inflammation in Diabetic Foot Ulcers

Despite the advancement in the treatment, nonhealing diabetic foot ulcers (DFUs) are an important clinical issue accounting for increased morbidity and risk of amputation. Persistent inflammation, decreased granulation tissue formation, decreased neo-angiogenesis, and infections are common underlying causes of the nonhealing pattern. Fibroblasts play a critical role in granulation tissue formation and angiogenesis and mediate wound healing how fibroblasts regulate inflammation in nonhealing DFUs is a question to ponder. This study aims to investigate the expression of a de-differentiated subpopulation of fibroblasts which are CD40+ (secretory fibroblasts) and increased secretion of IL-6 and IL-8 but have never been reported in DFUs. We characterized 11 DFU tissues and nearby clean tissues histologically and for the presence of inflammation and CD40+ fibroblasts using immunohistochemistry and RT-PCR. The results revealed significantly increased density of CD40+ fibroblasts and differential expression of mediators of inflammation in DFU tissues compared to clean tissue. Increased expression of IL-6, IL-1β, and TNF-α in DFU tissues along with CD40+ fibroblast suggest that CD40+ fibroblasts in DFUs contribute to the chronicity of inflammation and targeting fibroblasts phenotypic switch to decrease secretory fibroblasts may have therapeutic significance to promote healing.

Nano-Enabled Chronic Wound Healing Strategies: Burn and Diabetic Ulcer Wounds

The human skin serves as the body’s first line of defense against the environment. Diabetes mellitus (DM) and 2nd–4th degree burns, on the other hand, affect the skin’s protective barrier features. Burn wounds, hypermetabolic state, and hyperglycemia compromise the immune system leading to chronic wound healing. Unlike acute wound healing processes, chronic wounds are affected by reinfections which can lead to limb amputation or death. The conventional wound dressing techniques used to protect the wound and provide an optimal environment for repair have their limitations. Various nanomaterials have been produced that exhibit distinct features to tackle issues affecting wound repair mechanisms. This review discusses the emerging technologies that have been designed to improve wound care upon skin injury. To ensure rapid healing and possibly prevent scarring, different nanomaterials can be applied at different stages of healing (hemostasis, inflammation, proliferation, remodeling).

An Overview of Diabetic Foot Ulcers and Associated Problems with Special Emphasis on Treatments with Antimicrobials

One of the most significant challenges of diabetes health care is diabetic foot ulcers (DFU). DFUs are more challenging to cure, and this is particularly true for people who already have a compromised immune system. Pathogenic bacteria and fungi are becoming more resistant to antibiotics, so they may be unable to fight microbial infections at the wound site with the antibiotics we have now. This article discusses the dressings, topical antibacterial treatment, medications and debridement techniques used for DFU and provides a deep discussion of DFU and its associated problems. English-language publications on DFU were gathered from many different databases, such as Scopus, Web of Science, Science Direct, Springer Nature, and Google Scholar. For the treatment of DFU, a multidisciplinary approach involving the use of diagnostic equipment, skills, and experience is required. Preventing amputations starts with patient education and the implementation of new categorization systems. The microbiota involved in DFU can be better understood using novel diagnostic techniques, such as the 16S-ribosomal DNA sequence in bacteria. This could be achieved by using new biological and molecular treatments that have been shown to help prevent infections, to control local inflammation, and to improve the healing process.

Neutralizing Staphylococcus aureus Virulence with AZD6389, a Three mAb Combination, Accelerates Closure of a Diabetic Polymicrobial Wound

Nonhealing diabetic foot ulcers (DFU), a major complication of diabetes, are associated with high morbidity and mortality despite current standard of care. Since Staphylococcus aureus is the most common pathogen isolated from nonhealing and infected DFU, we hypothesized that S. aureus virulence factors would damage tissue, promote immune evasion and alter the microbiome, leading to bacterial persistence and delayed wound healing. In a diabetic mouse polymicrobial wound model with S. aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, we report a rapid bacterial proliferation, prolonged pro-inflammatory response and large necrotic lesions unclosed for up to 40 days. Treatment with AZD6389, a three-monoclonal antibody combination targeting S. aureus alpha toxin, 4 secreted leukotoxins, and fibrinogen binding cell-surface adhesin clumping factor A resulted in full skin re-epithelization 21 days after inoculation. By neutralizing multiple virulence factors, AZD6389 effectively blocked bacterial agglutination and S. aureus-mediated cell killing, abrogated S. aureus-mediated immune evasion and targeted the bacteria for opsonophagocytic killing. Neutralizing S. aureus virulence not only facilitated S. aureus clearance in lesions, but also reduced S. pyogenes and P. aeruginosa numbers, damaging inflammatory mediators and markers for neutrophil extracellular trap formation 14 days post initiation. Collectively, our data suggest that AZD6389 holds promise as an immunotherapeutic approach against DFU complications.

IMPORTANCE Diabetic foot ulcers (DFU) represent a major complication of diabetes and are associated with poor quality of life and increased morbidity and mortality despite standard of care. They have a complex pathogenesis starting with superficial skin lesions, which often progress to deeper tissue structures up to the bone and ultimately require limb amputation. The skin microbiome of diabetic patients has emerged as having an impact on DFU occurrence and chronicity. DFU are mostly polymicrobial, and the Gram-positive bacterium Staphylococcus aureus detected in more than 95% of cases. S. aureus possess a collection of virulence factors which participate in disease progression and may facilitate growth of other pathogens. Here we show in a diabetic mouse wound model that targeting some specific S. aureus virulence factors with a multimechanistic antibody combination accelerated wound closure and promoted full skin re-epithelization. This work opens promising new avenues for the treatment of DFU.

Bioactive Injectable Hydrogel Dressings for Bacteria-Infected Diabetic Wound Healing: A "Pull-Push" Approach

Chronic diabetic wound healing remains a challenge due to the existence of excessive danger molecules and bacteria in the inflammatory microenvironment. There is an urgent need for advanced wound dressings that target both inflammation and infection. Here, a bioactive hydrogel without loading any anti-inflammatory ingredients is rationally designed to achieve a "Pull-Push" approach for efficient and safe bacteria-infected diabetic wound healing by integrating danger molecule scavenging (Pull) with antibiotic delivery (Push) in the inflammatory microenvironment. The cationic hydrogel, termed the OCMC-Tob/PEI hydrogel, is fabricated by the conjugation of polyethylenimine (PEI) and tobramycin (Tob) on an oxidized carboxymethyl cellulose (OCMC) backbone via the Schiff base reaction with injectable, self-healing, and biocompatible properties. The OCMC-Tob/PEI hydrogel not only displays the remarkable capability of capturing multiple negatively charged danger molecules (e.g., cell-free DNA, lipopolysaccharides, and tumor necrosis factor-α) to ameliorate anti-inflammation effects but also achieves controllable long-term antibacterial activity by the pH-sensitive release of Tob. Consequently, this multifunctional hydrogel greatly expedites the wound closure rate with combined anti-inflammation and anti-infection effects on Pseudomonas aeruginosa-infected diabetic wounds. Our work provides a highly versatile treatment approach for chronic diabetic wounds and a promising dressing for regenerative medicine.

Diabetic foot ulcer, antimicrobial remedies and emerging strategies for the treatment

According to the International Diabetes Federation's 2015 study, diabetes affects over 415 million people globally (5 million of whom die each year), and the incidence of diabetes is expected to climb to over 640 million (1 in 10) by 2040. (IDF 2015). Diabetes foot ulcers (DFU) are one of the most significant diabetic health consequences. Antimicrobial treatments, such as dressings, topical therapies, medicines, drugs, debridement procedures, molecular, cellular, and gene therapies, plant extracts, antimicrobial peptides, growth factors, devices, ozone, and energy-based therapies, would be the focus of this study. Scopus, Web of Science, Bentham Science, Science Direct, and Google Scholar were among the sources used to compile the English-language publications on DFU. DFU treatment requires a multidisciplinary approach that includes the use of proper diagnostic tools, competence, and experience. To prevent amputations, this starts with patient education and the use of new categories to steer treatment. New diagnostic methods, such as the 16S ribosomal DNA sequence in bacteria, should become available to acquire a better knowledge of the microbiota in DFUs. 

Four in one-Combination therapy using live Lactococcus lactis expressing three therapeutic proteins for the treatment of chronic non-healing wounds

Diabetes mellitus is one of the major concerns for health care systems, affecting 382 million people worldwide. Among the different complications of diabetes, lower limbs chronic ulceration is a common, severe and costly cause of morbidity. Diabetic foot ulcers are a leading cause of hospitalization in diabetic patients and its rate exceed the ones of congestive heart failure, depression or renal disease. Diabetic non-healing ulcers account for more than 60% of all non-traumatic lower limb amputations and the five-year mortality after amputation is higher than 50%, being equal to several types of advanced cancer. The primary management goals for an existing diabetic foot ulcer are to achieve primary healing as expeditiously as possible and to achieve a reduction of the amputation rate in the patients. Unfortunately, approximately a quarter of patients do not partially or fully respond to the standard of care. Advanced therapies for chronic wounds are existing, however, recent guidelines including the latest reviews and meta-analyses of the scientific and clinical evidence available from current treatment strategies and new therapeutic agents revealed that there is a lack of clinical data and persistent gap of evidence for many of the advanced therapeutic approaches. In addition, no pharmacological wound healing product has gained authority approval for more than 10 years in both US and EU, constituting a highly unmet medical need. In this publication we present data from a live biopharmaceutical product AUP1602-C designed as a single pharmaceutical entity based on the non-pathogenic, food-grade lactic acid bacterium Lactococcus lactis subsp. cremoris that has been genetically engineered to produce human fibroblast growth factor 2,interleukin4 and colony stimulating factor 1. Designed to address different aspects of wound healing (i.e. fibroblast proliferation, angiogenesis and immune cell activation) and currently in phase I clinical study, we show how the combination of the individual components on the wound micro-environment initiates and improves the wound healing in chronic wounds.

The Gut-Skin Microbiota Axis and Its Role in Diabetic Wound Healing-A Review Based on Current Literature

Diabetic foot ulcers (DFU) are a growing concern worldwide as they pose complications in routine clinical practices such as diagnosis and management. Bacterial interactions on the skin surface are vital to the pathophysiology of DFU and may control delayed wound healing. The microbiota from our skin directly regulates cutaneous health and disease by interacting with the numerous cells involved in the wound healing mechanism. Commensal microbiota, in particular, interact with wound-repairing skin cells to enhance barrier regeneration. The observed microbes in DFU include Staphylococcus, Streptococcus, Corynebacterium, Pseudomonas, and several anaerobes. Skin commensal microbes, namely S. epidermidis, can regulate the gamma delta T cells and induce Perforin-2 expression. The increased expression of Perforin-2 by skin cells destroyed S. aureus within the cells, facilitating wound healing. Possible crosstalk between the human commensal microbiome and different cell types involved in cutaneous wound healing promotes the immune response and helps to maintain the barrier function in humans. Wound healing is a highly well-coordinated, complex mechanism; it can be devastating if interrupted. Skin microbiomes are being studied in relation to the gut-skin axis along with their effects on dermatologic conditions. The gut-skin axis illustrates the connection wherein the gut can impact skin health due to its immunological and metabolic properties. The precise mechanism underlying gut-skin microbial interactions is still unidentified, but the immune and endocrine systems are likely to be involved. Next-generation sequencing and the development of bioinformatics pipelines may considerably improve the understanding of the microbiome-skin axis involved in diabetic wound healing in a much more sophisticated way. We endeavor to shed light on the importance of these pathways in the pathomechanisms of the most prevalent inflammatory conditions including the diabetes wound healing, as well as how probiotics may intervene in the gut-skin axis.

Stress-Reducing Psychological Interventions as Adjuvant Therapies for Diabetic Chronic Wounds

BACKGROUND

Diabetic foot ulcers (DFUs) are a major complication of diabetes mellitus and a leading cause of lower limb amputation. Interventions to reduce psychological stress may have the potential to improve self-care and greatly reduce the morbidity and mortality associated with DFU. This review is focused on the consequences of psychological stress in wound healing and reflects on the effects of currently used psychological stress-reducing interventions in patients with DFU, proposing new applications for currently used stress-reduction interventions.

RESULTS

Stress is a natural and fundamental survival mechanism that becomes harmful when chronic. DFU is associated with high levels of anxiety and chronic psychological stress. Chronic stressinduced cortisol and adrenaline release impair wound healing, independently of the stressor. Psychological stress-reducing interventions, such as relaxation with guided imagery, biofeedback-assisted relaxation, mindfulness-based strategies, and hypnosis, can lead to a reduction in perceived stress and improve wound healing by reducing wound inflammation and pain while improving glycemic control. All stress reduction interventions also lead to pain relief and improved patient's quality of life.

CONCLUSION

Psychological stress-reducing interventions are promising adjuvant therapies for DFU. Their clinical application can improve self-care by tackling patient's expectations, anxieties, and fears. They can also help patients manage stress and pain while reducing wound inflammation and improving wound healing.

Human skin microbiota in health and disease: The cutaneous communities' interplay in equilibrium and dysbiosis: The cutaneous communities' interplay in equilibrium and dysbiosis

Cutaneous microbial composition is driven by the microenvironment of the skin, as well as by internal and external factors. Local changes in the microenvironment can affect the configuration of the community, which may lead toward an imbalance of microbiota. Alterations in the microbial profile are common in both inflammatory skin diseases and chronic infections. A shift in balance within the microbiota, toward limited variation and a greater abundance of specific pathogens, may further worsen the pathogenicity of the diseases. These alterations may be prevented by topical treatment of probiotic solutions stimulating a balanced multispecies community. Compositional variations may further constitute potential biomarkers to predict flares or monitor efficacy during therapy. New approaches such as machine learning may contribute to this prediction of microbial alterations prior to the development of chronic infections and flares. This review provides insight into the composition and distribution of a healthy community of microorganisms in the skin and draws parallels with the community in chronic infections and chronic inflammatory skin diseases such acne vulgaris and Hidradenitis Suppurativa. We discuss the potential role of specific species in the pathogenesis and the possible prevention of disease exacerbation.

Bioactive Antimicrobial Peptides as Therapeutic Agents for Infected Diabetic Foot Ulcers

Diabetic foot ulcer (DFU) is a devastating complication, affecting around 15% of diabetic patients and representing a leading cause of non-traumatic amputations. Notably, the risk of mixed bacterial–fungal infection is elevated and highly associated with wound necrosis and poor clinical outcomes. However, it is often underestimated in the literature. Therefore, polymicrobial infection control must be considered for effective management of DFU. It is noteworthy that antimicrobial resistance is constantly rising overtime, therefore increasing the need for new alternatives to antibiotics and antifungals. Antimicrobial peptides (AMPs) are endogenous peptides that are naturally abundant in several organisms, such as bacteria, amphibians and mammals, particularly in the skin. These molecules have shown broad-spectrum antimicrobial activity and some of them even have wound-healing activity, establishing themselves as ideal candidates for treating multi-kingdom infected wounds. Furthermore, the role of AMPs with antifungal activity in wound management is poorly described and deserves further investigation in association with antibacterial agents, such as antibiotics and AMPs with antibacterial activity, or alternatively the application of broad-spectrum antimicrobial agents that target both aerobic and anaerobic bacteria, as well as fungi. Accordingly, the aim of this review is to unravel the molecular mechanisms by which AMPs achieve their dual antimicrobial and wound-healing properties, and to discuss how these are currently being applied as promising therapies against polymicrobial-infected chronic wounds such as DFUs.

Photoactive electrospun cellulose acetate/polyethylene oxide/methylene blue and trilayered cellulose acetate/polyethylene oxide/silk fibroin/ciprofloxacin nanofibers for chronic wound healing

This study aimed to synthesize cellulose acetate (CA)-based electrospun nanofibers as drug delivery dressings for chronic wound healing. For the first time, CA was blended with polyethylene oxide (PEO) using acetone and formic acid. Methylene blue (MB) was incorporated into monolayered random CA/PEO nanofibers. They had a diameter of 400-600 nm, were hydrophilic, and generated reactive oxygen species upon irradiation. Thus, they mediated antimicrobial photodynamic inactivation (aPDI) against isolated biofilm-forming Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Bacterial survival, biofilm mass, and produced pyocyanin of the treated groups declined by 90%, 80%, and 3 folds, respectively. On the other hand, ciprofloxacin (Cipro) was loaded into an innovative trilayered aligned nanofiber consisting of CA/PEO surrounding a blank layer of silk fibroin. Cipro and MB release followed the Korsmeyer-Peppas model. An infected diabetic wound mouse model was established and treated with either MB-aPDI or Cipro. A combined therapy group of MB-aPDI followed by Cipro was included. The combined therapy showed significantly better results than monotherapies delineated by elevation in re-epithelization, collagen deposition, CD34, and TGF-β expression, along with a decline in CD95+ cells. This study deduced that drug-loaded CA electrospun nanofibers might be exploited in multimodal chronic wound healing.

Improvement of Chronic Wound Healing by Pre-activated Bone Marrow Cells with Sodium Nitroprusside in Rabbits

AIM OF STUDY

This study investigated whether pre-activated bone marrow cells with sodium nitro prusside have effectiveness in the inhibition of diabetic wound healing in diabetic rabbits. In diabetic skin disorders and conditions involved redox state disturbances. The aim was to determine the effect of two minimum dosages of sodium nitro prusside, and its' potential with bone marrow cells for chronic wound healing in-vivo.

METHODS

Full-thickness skin dorsal wounds were created on diabetic rabbits. The effects of two minimum concentrations of sodium nitro prusside solution with bone marrow cells on wound healing were studied. The useful combination of sodium nitro prusside with bone marrow cells on wound repair may be attributed to its functional influences on inflammation, angiogenesis, cell proliferation, matrix deposition, and remodeling.

RESULTS

The in-vivo experiments confirmed that pre-activated bone marrow cells contributed to wound healing by alleviating oxidative stress, increasing proliferation and migration, decreasing apoptosis. In histological results, improved collagen deposition, enhanced re-epithelization, angiogenesis, and decreased inflammatory infiltration were also detected in wound biopsies.

CONCLUSIONS

For the treatment of chronic wounds, cell-based therapy was an attractive approach. Bone marrow cells have a low ability to differentiate various types of cells or late healing without pretreatment. So it was needed to increase their potency of differentiation. The transplantation of pretreated bone marrow cells with a prime quantity of sodium nitro prusside solution improved chronic wound healing with a greater level of growth factors and a minimum level of oxidative stress.

Dual Action Gels Containing DsiRNA Loaded Gold Nanoparticles: Augmenting Diabetic Wound Healing by Promoting Angiogenesis and Inhibiting Infection

Hyperglycemia induces the prostaglandin transporter (PGT) gene overexpression, leading to poor vascularization and wound healing. Dicer substrate small interfering RNA (DsiRNA) and gold nanoparticles (AuNPs) co-loaded into PF127 gel was developed to overcome the disturbance and infections. The AuNPs were biosynthesized using cold and hot water extracts of Lignosus rhinocerotis (abbreviated CLRE and HLRE, respectively). The wound healing efficacy of a PF127 gel containing DsiRNA-AuNPs-CLRE and -HLRE (assigned as F2 and F3, respectively) was evaluated in a diabetes-induced Wistar rat model. The F2 (DC) and F3 (DH) treated groups revealed a faster wound closure (92.67 ± 3.4% and 85.1 ± 7.3%, respectively) than the positive control (commercial gel, DTI)(74.9 ± 13.3%). DH and DC groups presented an increased blood vessel density, along with decreased inflammatory cells. In comparison to positive control, higher prostaglandin E₂ (PGE₂) (495 ±79 and 50 ±121 pg/mL, for DC and DH group, respectively), vascular endothelial growth factor (VEGF) (49 ±15 and 38 ±3 pg/mL, for DC and DH group, respectively) and VEGF-A levels were detected in both groups (DC and DH), indicating the effectiveness of DsiRNA in enhancing PGE₂ production and vascularization. On evaluating microbiomes adhered to the wound areas, Gram-positive bacteria Staphylococcus and Corynebacterium, as well as Gram-negative Pseudomonas, Rodentibacter, and Acinetobacter, were found to be sensitive to the gel. Collectively, the gel was confirmed as a promising dressing for diabetic wound therapy, warranting further studies for clinical use.

The microbiology of diabetic foot infections: a meta-analysis

Background

Diabetic foot ulcers are a common complication of poorly controlled diabetes and often become infected, termed diabetic foot infection. There have been numerous studies of the microbiology of diabetic foot infection but no meta-analysis has provided a global overview of these data. This meta-analysis aimed to investigate the prevalence of bacteria isolated from diabetic foot infections using studies of any design which reported diabetic foot infection culture results.

Methods

The Medline, EMBASE, Web of Science and BIOSIS electronic databases were searched for studies published up to 2019 which contained microbiological culture results from at least 10 diabetic foot infection patients. Two authors independently assessed study eligibility and extracted the data. The main outcome was the prevalence of each bacterial genera or species.

Results

A total of 112 studies were included, representing 16,159 patients from which 22,198 microbial isolates were obtained. The organism most commonly identified was Staphylococcus aureus, of which 18.0% (95% CI 13.8–22.6%; I² = 93.8% [93.0–94.5%]) was MRSA. Other highly prevalent organisms were Pseudomonas spp., E. coli and Enterococcus spp. A correlation was identified between Gross National Income and the prevalence of Gram positive or negative organisms in diabetic foot infections.

Conclusion

The microbiology of diabetic foot infections is diverse, but S. aureus predominates. The correlation between the prevalence of Gram positive and negative organisms and Gross National Income could reflect differences in healthcare provision and sanitation. This meta-analysis has synthesised multiple datasets to provide a global overview of the microbiology of diabetic foot infections that will help direct the development of novel therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06516-7.

Biofilms in Diabetic Foot Ulcers: Impact, Risk Factors and Control Strategies

Diabetic foot ulcers (DFUs) are a serious complication from diabetes mellitus, with a huge economic, social and psychological impact on the patients' life. One of the main reasons why DFUs are so difficult to heal is related to the presence of biofilms. Biofilms promote wound inflammation and a remarkable lack of response to host defences/treatment options, which can lead to disease progression and chronicity. In fact, appropriate treatment for the elimination of these microbial communities can prevent the disease evolution and, in some cases, even avoid more serious outcomes, such as amputation or death. However, the detection of biofilm-associated DFUs is difficult due to the lack of methods for diagnostics in clinical settings. In this review, the current knowledge on the involvement of biofilms in DFUs is discussed, as well as how the surrounding environment influences biofilm formation and regulation, along with its clinical implications. A special focus is also given to biofilm-associated DFU diagnosis and therapeutic strategies. An overview on promising alternative therapeutics is provided and an algorithm considering biofilm detection and treatment is proposed.

Biofilm-Innate Immune Interface: Contribution to Chronic Wound Formation

Delayed wound healing can cause significant issues for immobile and ageing individuals as well as those living with co-morbid conditions such as diabetes, cardiovascular disease, and cancer. These delays increase a patient’s risk for infection and, in severe cases, can result in the formation of chronic, non-healing ulcers (e.g., diabetic foot ulcers, surgical site infections, pressure ulcers and venous leg ulcers). Chronic wounds are very difficult and expensive to treat and there is an urgent need to develop more effective therapeutics that restore healing processes. Sustained innate immune activation and inflammation are common features observed across most chronic wound types. However, the factors driving this activation remain incompletely understood. Emerging evidence suggests that the composition and structure of the wound microbiome may play a central role in driving this dysregulated activation but the cellular and molecular mechanisms underlying these processes require further investigation. In this review, we will discuss the current literature on: 1) how bacterial populations and biofilms contribute to chronic wound formation, 2) the role of bacteria and biofilms in driving dysfunctional innate immune responses in chronic wounds, and 3) therapeutics currently available (or underdevelopment) that target bacteria-innate immune interactions to improve healing. We will also discuss potential issues in studying the complexity of immune-biofilm interactions in chronic wounds and explore future areas of investigation for the field.

A comparative study of Helicobacter pylori infection in hamsters experimentally infected with liver flukes Opisthorchis felineus, Opisthorchis viverrini, or Clonorchis sinensis

Helicobacter pylori causes a wide range of human diseases including cancer. Carcinogenic foodborne trematodes Opisthorchis viverrini, Clonorchis sinensis, and O. felineus might promote transmission and spread of H. pylori infection in the definitive mammalian host, which in turn might contribute to the liver fluke-associated malignancy. Our objectives were to find out whether liver flukes O. felineus, O. viverrini, and C. sinensis are carriers of Helicobacter pylori and to determine whether H. pylori is present in feces, bile, and stomach samples from the experimentally infected hamsters. We found that liver flukes are not reservoirs of H. pylori. Nevertheless, the prevalence of H. pylori and the H. pylori ureA gene copy number were significantly elevated after the infection. Overall, although the liver flukes O. felineus, C. sinensis, and O. viverrini are not reservoirs of H. pylori, the infection with the liver flukes significantly modifies the biliary and gut microbiota by increasing H. pylori abundance. This may be a feature of any liver fluke pathogenesis that have not previously been taken into account. Our findings appear to be novel in terms of comparative assessment of the host microbiota and Helicobacter abundance during epidemiologically important liver fluke infections.

Adaptation of Staphylococcus aureus in a Medium Mimicking a Diabetic Foot Environment

Staphylococcus aureus is the most prevalent pathogen isolated from diabetic foot infections (DFIs). The purpose of this study was to evaluate its behavior in an in vitro model mimicking the conditions encountered in DFI. Four clinical S. aureus strains were cultivated for 16 weeks in a specific environment based on the wound-like medium biofilm model. The adaptation of isolates was evaluated as follows: by Caenorhabditis elegans model (to evaluate virulence); by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) (to evaluate expression of the main virulence genes); and by Biofilm Ring test^® (to assess the biofilm formation). After 16 weeks, the four S. aureus had adapted their metabolism, with the development of small colony variants and the loss of β-hemolysin expression. The in vivo nematode model suggested a decrease of virulence, confirmed by qRT-PCRs, showing a significant decrease of expression of the main staphylococcal virulence genes tested, notably the toxin-encoding genes. An increased expression of genes involved in adhesion and biofilm was noted. Our data based on an in vitro model confirm the impact of environment on the adaptation switch of S. aureus to prolonged stress environmental conditions. These results contribute to explore and characterize the virulence of S. aureus in chronic wounds.

Ex situ model of biofilm-associated wounds: providing a host-like environment for the study of Staphylococcus aureus and Pseudomonas aeruginosa biofilms

AIM

This study aimed to assess an ex situ model of biofilm-associated wounds on porcine skin for the study of Staphylococcus aureus and Pseudomonas aeruginosa biofilms in a host-like environment, after 48 to 120 h of incubation.

MATERIAL AND RESULTS

Ex situ and in vitro biofilms were comparatively analysed. Overall, CFU-counts and matrix quantification yielded significantly (P < 0·05) higher results for ex situ than in vitro biofilms. Confocal microscopy revealed greater (P < 0·05) biomass and thickness at 48-72 h and greater (P < 0·05) robustness at 72 h of growth. S. aureus ex situ biofilms produced less (P < 0·05) siderophore and proteases than in vitro biofilms, while P. aeruginosa ex situ biofilms produced more (P < 0·05) siderophores and less proteases than in vitro biofilms.

CONCLUSIONS

Biofilms grown ex situ present a greater amount of bacterial cells and polymeric matrix than their in vitro counterparts, reaching maturity at 72 h of growth. Moreover the production of virulence factors differs between ex situ and in vitro biofilms.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings emphasize the importance of using ex situ biofilm models, once they mimic in vivo conditions. The use of these models brings perspectives for the pursuit of therapeutic alternatives, as tests may be performed in a host-like environment.

The role of the microbiome in diabetes mellitus

The microbiome is greatly significant for immune system development and homeostasis. Dysbiosis in gut microbial composition and function is linked to immune responses and the development of metabolic diseases, including diabetes mellitus (DM). However, skin microbiome changes in diabetic patients and their role in DM are poorly elucidated. In this review, we summarize recent findings about the association between the gut and skin microbiota and DM, highlighting their roles in the proinflammatory status of DM. Moreover, although there is evidence that the connection between the gut and skin causes the same activated innate immune response, additional studies are needed to explore the mechanism. These findings might inform future DM prevention, diagnosis and treatment.

Microbiological profile of diabetic foot ulcers in Kuwait

Introduction

Diabetic foot ulcers (DFU) and infection (DFI) are a major diabetes-related problem around the world due to the high prevalence of diabetes in the population. The aim of our study was to determine the microbiological profile of infected ulcers in patients attending Dasman Diabetes Institute (DDI) clinics in Kuwait and to analyze the distribution of microbial isolates according to wound grade, sex, age and diabetes control.

Methods

We collected and analyzed clinical data and samples from 513 diabetic patients with foot ulcers referred to our podiatry clinic at DDI from Jan 2011 till Dec 2017.

Results

We show a higher prevalence of DFU in men than in women, and a greater percentage of DFU occurred in men at an earlier age (p<0.05). Only about half of the DFU were clinically infected (49.3%) but 92% of DFU showed bacterial growth in the microbiological lab analysis. In addition, we isolated more monomicrobial (57.3%) than polymicrobial (34.8%) DFI and representing an average of 1.30 pathogens per patient. The presence of Gram-positive and Gram-negative strains was comparable between men and women regardless their age or glucose levels. Interestingly, more Gram-positive strains are present in ulcers without ischemia while more Gram-negative strains are present in ulcers with ischemia (p<0.05). While Staphylococcus aureus was common in infected ulcers without ischemia, Pseudomonas aeruginosa was predominant in ulcers with infection and ischemia, regardless of ulcer depth. Finally, a higher percentage of women has controlled HbA1c levels (19.41% versus 11.95% in men) and more women in this group displayed non-infected wounds (60.6% and 43.90% for women and men, respectively).

Conclusion

Our results provide an updated picture of the DFI patterns and antibiotics resistance in patients attending Dasman Diabetes Institute (DDI) clinics in Kuwait which might help in adopting the appropriate treatment of infected foot and improving clinical outcomes.

The dynamic wound microbiome

BACKGROUND

Diabetic foot ulcers (DFUs) account for the majority of all limb amputations and hospitalizations due to diabetes complications. With 30 million cases of diabetes in the USA and 500,000 new diagnoses each year, DFUs are a growing health problem. Diabetes patients with limb amputations have high postoperative mortality, a high rate of secondary amputation, prolonged inpatient hospital stays, and a high incidence of re-hospitalization. DFU-associated amputations constitute a significant burden on healthcare resources that cost more than 10 billion dollars per year. Currently, there is no way to identify wounds that will heal versus those that will become severely infected and require amputation.

MAIN BODY

Accurate identification of causative pathogens in diabetic foot ulcers is a critical component of effective treatment. Compared to traditional culture-based methods, advanced sequencing technologies provide more comprehensive and unbiased profiling on wound microbiome with a higher taxonomic resolution, as well as functional annotation such as virulence and antibiotic resistance. In this review, we summarize the latest developments in defining the microbiology of diabetic foot ulcers that have been unveiled by sequencing technologies and discuss both the future promises and current limitations of these approaches. In particular, we highlight the temporal patterns and system dynamics in the diabetic foot microbiome monitored and measured during wound progression and medical intervention, and explore the feasibility of molecular diagnostics in clinics.

CONCLUSION

Molecular tests conducted during weekly office visits to clean and examine DFUs would allow clinicians to offer personalized treatment and antibiotic therapy. Personalized wound management could reduce healthcare costs, improve quality of life for patients, and recoup lost productivity that is important not only to the patient, but also to healthcare payers and providers. These efforts could also improve antibiotic stewardship and control the rise of "superbugs" vital to global health.

Biofilms in Diabetic Foot Ulcers: Significance and Clinical Relevance

Foot infections are the main disabling complication in patients with diabetes mellitus. These infections can lead to lower-limb amputation, increasing mortality and decreasing the quality of life. Biofilm formation is an important pathophysiology step in diabetic foot ulcers (DFU)-it plays a main role in the disease progression and chronicity of the lesion, the development of antibiotic resistance, and makes wound healing difficult to treat. The main problem is the difficulty in distinguishing between infection and colonization in DFU. The bacteria present in DFU are organized into functionally equivalent pathogroups that allow for close interactions between the bacteria within the biofilm. Consequently, some bacterial species that alone would be considered non-pathogenic, or incapable of maintaining a chronic infection, could co-aggregate symbiotically in a pathogenic biofilm and act synergistically to cause a chronic infection. In this review, we discuss current knowledge on biofilm formation, its presence in DFU, how the diabetic environment affects biofilm formation and its regulation, and the clinical implications.

A Review on Revolutionary Natural Biopolymer-Based Aerogels for Antibacterial Delivery

A biopolymer-based aerogel has been developed to become one of the most potentially utilized materials in different biomedical applications. The biopolymer-based aerogel has unique physical, chemical, and mechanical properties and these properties are used in tissue engineering, biosensing, diagnostic, medical implant and drug delivery applications. Biocompatible and non-toxic biopolymers such as chitosan, cellulose and alginates have been used to deliver antibiotics, plants extract, essential oils and metallic nanoparticles. Antibacterial aerogels have been used in superficial and chronic wound healing as dressing sheets. This review critically analyses the utilization of biopolymer-based aerogels in antibacterial delivery. The analysis shows the relationship between their properties and their applications in the wound healing process. Furthermore, highlights of the potentials, challenges and proposition of the application of biopolymer-based aerogels is explored.

Role and effect of vein-transplanted human umbilical cord mesenchymal stem cells in the repair of diabetic foot ulcers in rats

Diabetic foot ulcer (DFU) is one of diabetic complications, which is frequently present and tormented in diabetes mellitus. Most multipotent mesenchymal stromal cells (MSCs) are capable of immune evasion, providing an allogeneic, ready-to-use, cell product option for therapeutic applications. The beneficial effect of MSCs for the treatment of a variety of traumatic injuries, such as open wounds, has been extensively explored. In this study, a rat DFU model was used to simulate the pathophysiology of clinical patients and to investigate the localization of human umbilical cord mesenchymal stem cells (hUC-MSCs) after intravenous transplantation and its role in DFU healing, so as to evaluate the potential of hUC-MSCs in the treatment of DFU. The diabetic rat model was established by streptozotocin injection, which was used to create full-thickness foot dorsal skin wounds to mimic DFU by a 6-mm skin biopsy punch and a Westcott scissor. The hUC-MSCs were transplanted through femoral vein, and the ulcer cicatrization situation and the fate of hUC-MSCs were evaluated. Our data suggest that intravenously transplantated hUC-MSCs have the ability to migrate and locate to the wound tissue and are helpful to wound healing in DFU rats, partly by regulating inflammation, trans-differentiation and providing growth factors that promote angiogenesis, cell proliferation and collagen deposition. Herein, we demonstrate that hUC-MSC transplantation is able to accelerate DFU healing in rats and transplantation of exogenous stem cells may be a potential strategy for clinical application in DFUs.

Lack of lymphocytes impairs macrophage polarization and angiogenesis in diabetic wound healing

AIMS

This study aimed to investigate the effect of lymphocytes in wound healing and the underlying mechanisms, in diabetic and non-diabetic mice, using Balb/c recombination activating gene (Rag)-2 and interleukin 2 receptor gamma (IL-2Rγ) double knockout (KO) (RAG2^-/- IL-2Rγ^-/-) mice.

MAIN METHODS

Wound healing in vivo was performed in control and STZ-induced diabetic mice, in both KO and WT mice. Inflammation and ROS production were evaluated by immunofluorescence microscopy analysis, antioxidant enzymes and angiogenesis were evaluated by quantitative PCR and immunofluorescence microscopy analysis, and wound closure kinetics evolution was evaluated by measurement of acetate tracing of the wound area.

KEY FINDINGS

Wound closure was significantly delayed in KO mice, where the M1/M2 macrophage ratio and basal ROS levels were significantly increased, while antioxidant defenses and angiogenesis were significantly decreased. Moreover, the expected increase in matrix metallopeptidase (MMP)-9 protein levels in diabetic conditions was not observed in KO mice, suggesting that the mechanisms leading to the increase in MMP-9 observed in diabetic wounds may in part be lymphocyte-dependent.

SIGNIFICANCE

Our results indicate that lack of lymphocytes compromises wound healing independent of diabetes. The lack of these cells, even in non-diabetic mice, mimics the phenotype observed in wounds under diabetic conditions. Moreover, the combination of diabetes and the lack of lymphocytes, further impair the wound healing conditions, indicating that when the innate regulatory function is lost in these KO mice, excessive M1 polarization, poor angiogenesis and impaired wound healing are worsen.

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

Background

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

Methods

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

Results

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

Conclusions

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

Microbial Community Distribution and Core Microbiome in Successive Wound Grades of Individuals with Diabetic Foot Ulcers

Diabetic foot ulcer (DFU) is a major complication of diabetes with high morbidity and mortality rates. The pathogenesis of DFUs is governed by a complex milieu of environmental and host factors. The empirical treatment is initially based on wound severity since culturing and profiling the antibiotic sensitivity of wound-associated microbes is time-consuming. Hence, a thorough and rapid analysis of the microbial landscape is a major requirement toward devising evidence-based interventions. Toward this, 122 wound (100 diabetic and 22 nondiabetic) samples were sampled for their bacterial community structure using both culture-based and next-generation 16S rRNA-based metagenomics approach. Both the approaches showed that the Gram-negative microbes were more abundant in the wound microbiome. The core microbiome consisted of bacterial genera, including Alcaligenes, Pseudomonas, Burkholderia, and Corynebacterium in decreasing order of average relative abundance. Despite the heterogenous nature and extensive sharing of microbes, an inherent community structure was apparent, as revealed by a cluster analysis based on Euclidean distances. Facultative anaerobes (26.5%) were predominant in Wagner grade 5, while strict anaerobes were abundant in Wagner grade 1 (26%). A nonmetric dimensional scaling analysis could not clearly discriminate samples based on HbA1c levels. Sequencing approach revealed the presence of major culturable species even in samples with no bacterial growth in culture-based approach. Our study indicates that (i) the composition of core microbial community varies with wound severity, (ii) polymicrobial species distribution is individual specific, and (iii) antibiotic susceptibility varies with individuals. Our study suggests the need to evolve better-personalized care for better wound management therapies.IMPORTANCE Chronic nonhealing diabetic foot ulcers (DFUs) are a serious complication of diabetes and are further exacerbated by bacterial colonization. The microbial burden in the wound of each individual displays diverse morphological and physiological characteristics with unique patterns of host-pathogen interactions, antibiotic resistance, and virulence. Treatment involves empirical decisions until definitive results on the causative wound pathogens and their antibiotic susceptibility profiles are available. Hence, there is a need for rapid and accurate detection of these polymicrobial communities for effective wound management. Deciphering microbial communities will aid clinicians to tailor their treatment specifically to the microbes prevalent in the DFU at the time of assessment. This may reduce DFUs associated morbidity and mortality while impeding the rise of multidrug-resistant microbes.

A novel peptide from the skin of amphibian Rana limnocharis with potency to promote skin wound repair

In clinical trials, the healing of wounds remains a substantial physiological and financial incumbrance on patients. Therefore, the development of new drugs that can accelerate wound healing is vital. Based on genomic methods, we identified a new peptide (RL-RL10) with the amino acid sequence 'RLFKCWKKDS' from the skin of an amphibian frog species (Rana limnocharis). RL-RL10 promoted wound healing of human keratinocytes (HaCaT) in a concentration-dependent manner. RL-RL10 also had an effect on the migration and proliferation of HaCaT cells and promoted healing of a full-thickness wound in mice in a dose-dependent manner. In conclusion, we discovered RL-RL10 that promoted healing activity of cellular and animal wounds, thus providing a new peptide template for the development of novel wound-repairing drugs.

Differences in foot skin microbiomes between patients with type 2 diabetes and healthy individuals

Impaired immunity and changes in the microenvironment in patients with diabetes might influence the composition of the cutaneous microbiome. However, data on the cutaneous microbiome of these patients are scarce. This study compared the fungal and bacterial components of the skin microbiome between patients with type 2 diabetes mellitus (DM) and healthy individuals. We obtained skin swab samples from the plantar forefoot of 17 patients with DM and 18 healthy individuals to conduct a cross-sectional study. The samples were profiled with culture-independent sequencing of the V3 to V4 regions of the bacterial 16S rRNA gene and the fungal ITS2 region, followed by direct DNA extraction and molecular polymerase chain reaction (PCR). We observed a differential cutaneous microbiome, especially for fungi, in patients with type 2 diabetes compared to that in healthy controls. Trichophyton rubrum was more abundant in DM samples. The Shannon diversity index for fungi was lower in the DM patients. Principal coordinate analysis plots and permutational multivariate analysis of variance (PERMANOVA) tests based on Bray-Curtis distances between samples supported the association of the fungal microbiome with DM at the species level. The results suggest that clinicians should pay attention to both fungi and bacteria and provide appropriate prevention and therapeutic strategies for diabetic cutaneous complications including diabetic foot ulcers. These data also contribute to future research associated with diabetes and cutaneous microbiomes.

Alterations of the human skin microbiome after ocean water exposure

Skin is the body's first line of defense against invading microorganisms. The skin microbiome has been shown to provide immunity against exogenous bacterial colonization. Recreational water exposures may alter the skin microbiome and potentially induce skin infections. This study explored the link between ocean water exposures and the human skin microbiome. Skin microbiome samples were collected, using swabs, from human participants' calves before and after they swam in the ocean, and at 6 hour and 24 hour post-swim. Genomic analysis showed that skin microbiomes were different among individuals before swimming. But after swimming, microbial communities were no longer different, which was demonstrated by a decrease in inter-sample diversity. Taxonomic analysis showed that ocean bacteria, including potential pathogens, replaced the native skin bacteria and remained on the skin for at least 24 hour post-swim. This research provides insight into the relationship between the human skin microbiome and the environment.

Microbiome Imbalances: An Overlooked Potential Mechanism in Chronic Nonhealing Wounds

Chronic nonhealing wounds are a severe burden to health care systems worldwide, causing millions of patients to have lengthy hospital stays, high health care costs, periods of unemployment, and reduced quality of life. Moreover, treating chronic nonhealing wounds effectively and reasonably in countries with limited medical resources can be extremely challenging. With many outstanding questions surrounding chronic nonhealing wounds, in this review, we offer changes to the microbiome as a potentially ignored mechanism important in the formation and treatment of chronic wounds. Our analysis helps bring a whole new understanding to wound formation and healing and provides a potential breakthrough in the treatment of chronic nonhealing wounds in the future.

Management of bacterial skin and skin structure infections with polymicrobial etiology

INTRODUCTION

Skin and Soft Tissue Infections (SSTIs) are some of the most commonly occurring bacterial infections, with a wide range of possible etiological pathogens and a considerable variety of clinical presentations and severity; from mild to severe life-threatening infections. Several classifications have been proposed based on a specific variable, such as anatomical localization, skin extension, progression rate, clinical presentation, severity, and etiological agent. Areas covered: The last criteria allows the differentiation of SSTIs as monomicrobial and polymicrobial. Among them, especially those infections with a long lasting or chronic course can be sustained by multiple microbial etiology. Most polymicrobial SSTIs can be included in the following: diabetes foot infections (DFIs), pressure ulcers infection, burn infection, and infected chronic ulcers. Expert commentary: The medical management of these infections comprises the administration of wide a spectrum antibiotic, taking into consideration the frequent occurrence of multidrug resistant microorganisms as responsible agents. An appropriate deep tissue specimen for microbiological examination is a very important issue, especially for polymicrobial infections, sometimes permitting the distinction between real pathogens and contaminants avoiding more complex antibiotic treatments. This aspect must be strongly emphasized, as frequently superficial swabs remain the specimen of choice because they are easy to obtain.

Performance of the automated multiplex PCR Unyvero implant and tissue infections system in the management of diabetic foot osteomyelitis

AIM

We evaluated the performance of Unyvero implant and tissue infections system (ITI) application (Curetis) to diagnose Diabetic Foot Osteomyelitis (DFOM).

PATIENTS & METHODS

The study was conducted in the Diabetic Foot reference center of Nîmes University Hospital (France) from 1 December 2016 to 31 May 2017. We compared the Unyvero ITI PCR to conventional culture and alternative molecular approaches.

RESULTS

A total of 79 patients with DFOM were included: 177 microorganisms were isolated by culture, 146 detected by PCR, resulting in a concordance level of 66.7% (65.0-68.4). Discrepant results were obtained for 45 samples, with 59 microorganisms being detected by PCR only (18 samples) or by culture only (27 samples).

CONCLUSION

Unyvero ITI PCR represents an interesting additional diagnosis solution to manage DFOM.