Hot topics in diabetic foot infection

Engineered exosomes as a prospective therapy for diabetic foot ulcers

Diabetic foot ulcer (DFU), characterized by high recurrence rate, amputations and mortality, poses a significant challenge in diabetes management. The complex pathology involves dysregulated glucose homeostasis leading to systemic and local microenvironmental complications, including peripheral neuropathy, micro- and macro-angiopathy, recurrent infection, persistent inflammation and dysregulated re-epithelialization. Novel approaches to accelerate DFU healing are actively pursued, with a focus on utilizing exosomes. Exosomes are natural nanovesicles mediating cellular communication and containing diverse functional molecular cargos, including DNA, mRNA, microRNA (miRNA), lncRNA, proteins, lipids and metabolites. While some exosomes show promise in modulating cellular function and promoting ulcer healing, their efficacy is limited by low yield, impurities, low loading content and inadequate targeting. Engineering exosomes to enhance their curative activity represents a potentially more efficient approach for DFUs. This could facilitate focused repair and regeneration of nerves, blood vessels and soft tissue after ulcer development. This review provides an overview of DFU pathogenesis, strategies for exosome engineering and the targeted therapeutic application of engineered exosomes in addressing critical pathological changes associated with DFUs.

Comparison of different concentrations of chlorhexidine-iodophor composite solution on human skin fibroblasts

OBJECTIVE

Chlorhexidine-iodophor (CHX-IP) composite solution is a polymer of chlorhexidine and iodophor produced with new technology, for use in diabetic foot infection. However, the effect of CHX-IP on the growth activity of fibroblasts remains unknown, thus the effects of different concentrations of CHX-IP composite solution on the viability and micromorphology of human skin fibroblasts were studied in vitro cell culture in this study.

METHOD

A cell viability assay was applied to calculate cell viability and an inverted fluorescence microscope was used to observe cell morphology over five days.

RESULTS

The results showed that the toxic effect of CHX-IP on fibroblasts was solution concentration-dependent and decreased over time. When the concentration of CHX-IP was 5.0mg/ml, 2.5mg/ml, 0.625mg/ml, 0.15625mg/ml, 0.078125mg/ml or 0mg/ml, the difference of optical density (OD) value on different days was statistically significant (p<0.05). There were statistically significant differences in the OD value of fibroblasts among different concentrations of CHX-IP on: day 2 (F=4.809, p=0.004); day 3 (F=21.508, p<0.001); day 4 (F=63.952, p<0.001); and day 5 (F=160.407, p<0.001). In addition, a concentration of 5.0mg/ml CHX-IP resulted in a fibroblastic viability rate of 0% on day 4, when CHX-IP was diluted to 2.5mg/ml or 1.25 mg/ml, fibroblastic viability rate decreased to 0% day 5. However, when the CHX-IP was diluted to 0.15625mg/ml or 0.078125mg/ml, the fibroblastic cell viability rate increased slightly on day 5. The morphology of cells observed under microscope indirectly supported this result.

CONCLUSION

The findings of this study showed that the toxic effect of CHX-IP on fibroblasts was solution concentration-dependent and decreased over time.

Stem Cell-Based Tissue Engineering Approaches for Diabetic Foot Ulcer: a Review from Mechanism to Clinical Trial

Diabetic foot ulcer (DFU) is a complication from incomplete or prolonged wound healing, at times requires amputation, putting substantial health and socioeconomic burden. Wound healing is a dynamic overlapping process that can be regulated by arrays of molecular factors showing redundancy in function. However, dysregulation in the mechanism of angiogenesis, extra cellular matrix (ECM) formation and immune modulation are the major causes for impair wound healing in hyperglycaemic patients. Despite development of wound care research, there is a lack of well-accepted targeted therapy with multidisciplinary approach for DFU treatment. Stem cell therapy holds a promising outcome both in preclinical and clinical trials because of its ability to promote healing via regeneration and specialized tissue differentiation. Among different types of stem cells, regenerative potential of mesenchymal stem cell (MSC) is well demonstrated in both experimental and clinical trial. Still there is a huge knowledge gap among medical practitioners for deciding the best stem cell source, administration route, and safety. This review strengthens the fact that why stem cell therapy is a promising candidate to treat DFU and cited multiple tissue engineering and biomaterial-based approaches for delivering stem cells and their aftermath paracrine events. Based on the pre-clinical and clinical studies, the review tried to come up with optimum stem cell source and delivery route for the treatment of DFU. At last, the review glances on possible direction to enhance therapeutics strategy for the same, including different approaches like: phytocompounds, exosomes, scaffold geometry, cell preconditioning and licensing etc.

Effectiveness of continuous home wound care on wound healing, self-management behavior, and medical expenses of patients with diabetic foot ulcers

OBJECTIVE

To explore the effectiveness of continuous home wound care on wound healing, self-management behavior, and medical expenses of patients with diabetic foot ulcers.

MATERIALS AND METHODS

Patients were grouped by the campuses they were hospitalized. One group received home wound care, and the other one received outpatient wound care after their discharge. Non-inferiority testing was performed to compare ulcer healing. Their Diabetes-related Foot Ulcer Self-Management Behavior Scale (DFUSMBS) scores and medical expenses were compared.

RESULTS

Between October 2021 and December 2022, fifty-five patients in the home wound care group and fifty-two in the outpatient wound care group completed the study. The home wound care was non-inferior concerning ulcer complete healing rate in total or stratified by Wagner grade or baseline ulcer area. Concerning wound healing time, the home wound care group was inferior for Wagner Grade Ⅲ ulcers (hazard ratio = 0.7772, 95 % CI = 0.2799-2.1581). In contrast, for ulcers with baseline area>5 cm2, the home care group was non-inferior and even can be superior, although the superiority was not statistically significant (Log-rank X2 = 0.257, p = 0.612). Moreover, the home wound care group showed significant improvement concerning timely wound treatment (t = 23.045, p < 0.001, Cohen's d = 4.460, Effect Size = 0.912) and wound care behavior (t = 33.410, p < 0.001, Cohen's d = 6.454, Effect Size = 0.955), while that of diabetes self-management was not statistically significant (t = -0.673, p = 0.502, Cohen's d = 0.128, Effect Size = 0.064). The medium direct medical expense per capita of the patients in the outpatient care group was statistically significantly heavier than that of the home wound care group (Z = -6.877, p < 0.001).

CONCLUSION

The home wound care practice did not compromise ulcer healing, enhanced timely wound treatment and wound care behavior of the patients, and saved their medical expenses, hopefully providing a feasible wound care alternative with economic benefits for the physically and economically devastated patients.

Relative Abundance and Detection of Pseudomonas aeruginosa from Chronic Wound Infections Globally

Pseudomonas aeruginosa is a difficult-to-treat pathogen that is frequently involved with chronic wound infections. Here, we conducted a literature search of world-wide studies published between 2005 and 2022 that described the microbiological profiles of chronic wound infections. For each continent, a hierarchy of pathogens was created to define the organisms that were most frequently isolated in each region. Except for South America, P. aeruginosa was the second most common organism in each major continent, with Staphylococcus aureus being the most abundant pathogen overall. When individual countries were evaluated, P. aeruginosa was the most frequently isolated organism in several Southeast Asia nations including India and Malaysia. P. aeruginosa was less commonly isolated from diabetic foot infections in North America, Europe, and Africa in comparison to other types of chronic wound infections. Additionally, the Levine wound swab technique may be a quick and painless way to isolate P. aeruginosa from wound infections, but the isolation of P. aeruginosa does not seem to be an informative predictor of the patient's clinical course. A multivariate risk assessment that accounts for the regional frequency of P. aeruginosa isolation may be an appropriate way to guide empiric management of chronic wound infections.

Interspecies interactions in mixed-species biofilms formed by Enterococcus faecalis and gram-negative bacteria isolated from polymicrobial diabetic foot ulcers

Diabetic foot ulcers (DFU) are exacerbated by bacterial colonisation. Here, a high prevalence of Enterococcus faecalis was observed in DFU patients from an Argentinean hospital. E. faecalis was frequently co-isolated with Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa. The effect of interspecies interactions on bacterial growth was investigated in mixed-species macrocolony biofilms developed in Lubbock-Glc-agar. Similar cell counts were found for E. faecalis and M. morganii growing in mixed and single-species biofilms. An E. faecalis strain showed 1 Log higher cell counts in mixed biofilms with E. coli. Remarkably, E. faecalis strains showed 2 to 4 Log higher cell counts in mixed biofilms with P. aeruginosa. This effect was not observed in planktonic growth or biofilms developed in tryptic soy agar. The present findings reveal bacterial interactions that benefit E. faecalis in mixed-species biofilms, mainly with P. aeruginosa, in a medium that partially mimics the nutrients found in DFU.

A scientometrics analysis and visualisation of diabetic foot research from 1955 to 2022

Diabetic foot (DF) has become a serious health problem in modern society, and it has been a hotspot of research for a long time. However, little scientometric analysis has been carried out on DF. In the present study, we analysed 8633 literature reports on DF in the Web of Science Core Collection from database inception until April 23, 2022. VOSviewer (Centre for Science and Technology Studies at Leiden University, Leiden, the Netherlands) and CiteSpace (College of Computing and Informatics, Drexel University, Philadelphia, United States) were employed to address high-impact countries and institutions, journals, references, research hotspots, and key research fields in DF research. Our analysis findings indicated that publications on DF have increased markedly since 2016 and were primarily published in the United States of America. The recent studies focus on the amniotic membrane, foot ulcers, osteomyelitis, and diabetic wound healing. The five keyword clusters, which included DF ulcer and wound healing therapies, management and guidelines, neuropathy and plantar pressure, amputation and ischemia, and DF infection and osteomyelitis, are helpful for enhancing prevention, standardising treatment, avoiding complications, and improving prognosis. These findings indicated a method for future therapies and research in DF.

Autophagy ameliorates Pseudomonas aeruginosa-infected diabetic wounds by regulating the toll-like receptor 4/myeloid differentiation factor 88 pathway

Diabetic foot ulcers (DFUs) are among the most common complications in patients with diabetes and a leading cause of lower extremity amputation. DFUs are exacerbated by prolonged bacterial infection; therefore, there is an urgent need for effective treatments to alleviate the burden associated with this condition. Although autophagy plays a unique role in pathogen phagocytosis and inflammation, its role in diabetic foot infections (DFIs) remains unclear. Pseudomonas aeruginosa (PA) is the most frequently isolated gram-negative bacterium from DFUs. Here, we evaluated the role of autophagy in ameliorating PA infection in wounds in a diabetic rat model and a bone marrow-derived macrophage (BMDM) hyperglycemia model. Both models were pretreated with or without rapamycin (RAPA) and then infected with or without PA. Pretreatment of rats with RAPA significantly enhanced PA phagocytosis, suppressed wound inflammation, reduced the M1:M2 macrophage ratio, and improved wound healing. In vitro investigation of the underlying mechanisms revealed that enhanced autophagy resulted in decreased macrophage secretion of inflammatory factors such as TNF-α, IL-6, and IL-1β but increased that of IL-10 in response to PA infection. Additionally, RAPA treatment significantly enhanced autophagy in macrophages by increasing LC3 and beclin-1 levels, which led to altered macrophage function. Furthermore, RAPA blocked the PA-induced TLR4/MyD88 pathway to regulate macrophage polarisation and inflammatory cytokine production, which was validated by RNA interference and use of the autophagy inhibitor 3-methyladenine (3-MA). These findings suggest enhancing autophagy as a novel therapeutic strategy against PA infection to ultimately improve diabetic wound healing.

The first experience of using a comprehensive detailed ultrasound examination of the foot in patients with diabetes mellitus

INTRODUCTION

Assessment of amputation risk has been discussed more than once in the management of patients with diabetes. Systemic inflammatory symptoms can serve as signs of an infectious process. However, not all patients show exhibit these symptoms in a timely manner. At the same time, a decrease in pain, tactile and temperature sensitivity fails as a part of the main assessment of risk factors in diabetes mellitus.

METHODS

Using examination methods and comparing with clinical experience and the results of other researchers, a pilot study was carried out to diagnose structural changes in the foot in patients with diabetes. Nested examinations were carried out in several stages, on the expert class medical ultrasonographic apparatus Siemens Acuson NX3. The methods of ultrasound diagnostics in the diabetic foot can be significantly helpful when using a scale of criteria and guidelines for the examination.

CONCLUSION

The main diagnostic criterion for determining the risks of developing a diabetic foot condition, could be a gradual transition from the phase of compaction of hyaline cartilage to the phase of synovitis, and then to the phase of development of bone tissue necrosis related to a part of the Charcot's foot. It leads to disruption of the musculoskeletal system of the foot, and atherosclerotic plaques and stenosis of the dorsalis pedis artery and first toe, which form a deterioration in the nutrition of the soft tissues of the foot with their necrosis.

Factors Associated with Infection Severity of Diabetic Foot Ulcers: A Cross-Sectional Study

Background: Infection in the ulcerated foot is a foremost cause of morbidity, constituting the biggest proportion of hospitalization and amputation among patients with diabetic foot ulcers. Assessment of infection severity lays a foundation for making treatment decisions, for which the IDSA/IWGDF classification is recommended. Different factors may cause various severity of infection. However, few investigations have been conducted concerning factors associated with infection severity of diabetic foot ulcers. Objective: To investigate factors associated with infection severity of diabetic foot ulcers. Methods: This cross-sectional study involved 150 subjects hospitalized in the Department of Endocrinology of Sun Yat-sen Memorial Hospital in Guangdong Province between July 2020 and September 2021. The IDSA/IWGDF classification was adopted to assess ulcer infection severity. Demographic and disease information, laboratory reports, and ulcer assessment results were evaluated for an association with the infection severity. The generalized linear model was performed to conduct multivariate analyses of the factors associated with the severity of foot infection. Results: The prevalence of mild, moderate, and severe infected diabetic foot was 23.3%, 64.7% and 10.2%, respectively. The results of generalized linear models showed a correlation between Alb (OR = -1.74, 95%CI1.12-6.58, p = .023), CRP (OR = 2.13, 95%CI1.38-7.21, p = .014), PCT (OR = 2.01, 95%CI1.29-7.64, p = .013), microbial type (OR = 2.04, 95%CI1.43-7.83, p = .004) and ulcer infection severity. Conclusion: Alb, CRP, PCT and microbial type were among the factors influencing infection severity of diabetic foot ulcers.

Effects of Chlorhexidine-Iodophor Composite Solution on the Viability and Proliferation of Human Skin Fibroblasts Infected by S. aureus - An in Vitro Experiment

Background: The chlorhexidine-iodophor (CHX-IP) composite solution is a polymer of chlorhexidine and iodophor, applicable to the control of local microbial load and probably toxic to fibroblasts. However, the effect of CHX-IP on the viability and proliferation of human skin fibroblasts infected by Staphylococcus aureus (S. aureus) remains unknown. Objective: The effects of CHX-IP composite solution on the viability and proliferation of human skin fibroblasts infected by S. aureus were investigated in vitro cell culture in this study. Methods: Optimum multiplicity of infection (MOI) was determined to construct the S. aureus-fibroblast co-culture model. Cell Viability Assay was applied to obtain optical density (OD) value and calculate cell viability. 5-ethynyl-2'- deoxyuridine (EdU) assay was used to investigate the effect of CHX-IP on the proliferation of human skin fibroblasts infected by S. aureus. Results: 10:1 was the optimum MOI for the S. aureus-fibroblast co-culture model. The OD value of human skin fibroblasts infected by S. aureus increased in the blank control group, 0.625 mg/ml, 0.3125 mg/ml, 0.15625 mg/ml, and 0.075625 mg/ml groups after four hours. While that of the negative control group, 5 mg/ml, 2.5 mg/ml, and 1.25 mg/ml groups decreased over time. The two-way ANOVA results indicated that the OD value of human skin fibroblasts infected by S. aureus was significantly different among different CHX-IP concentration groups (F = 34.05, P < .001), and the interaction effect between concentration and time was significant (F = 9.442, P < .001). The results of the EdU cell proliferation assay showed that the blank control group, 0.625 mg/ml CHX-IP group, and 0.075625 mg/ml CHX-IP group had an enhanced fibroblasts cell proliferation, while the fibroblasts cell proliferation of the negative control group and 5 mg/ml CHX-IP group was inhibited. Conclusion: The viability and proliferation of human skin fibroblasts infected by S. aureus were inhibited, while specific concentrations of CHX-IP solution can counteract or even reverse the proliferation inhibition effect.

Clinical usefulness of quantifying microbial load from diabetic foot ulcers: A multicenter cohort study

AIMS

To evaluate if microbial load from diabetic foot ulcers (DFUs) can help in predicting outcomes.

METHODS

A multicenter prospective cohort study was performed in an outpatient setting (September 1, 2017-January 31, 2019) in diabetic patients with DFU.Quantitative cultures from DFU tissue biopsies at a baseline visit were obtained; high and low microbial loads were defined as ≥6logCFU/mL and <6logCFU/mL, respectively. Diagnosis of DFU infection was made and managed according to established guidelines. The outcome was evaluated at 6 month-visit as failure (persistence/new infection/amputation) or cure.

RESULTS

Out of 65 patients, 52 (80%) had long-standing DFUs (≥4 weeks), with high microbial load in 19 (29%).DFU infection (n = 24, 37%) was not associated with high microbial load in all patients but those with shorter DFU duration.Treatment failure occurred in 20/57 (35%) patients; high DFU microbial load was associated with worse outcome (n = 9/20, 45% failure rate, adjusted OR4.69; 95% CI, 1.22-18.09; p = 0.03),mainly due to the subgroup of patients with high microbial load and long-stand DFUs.

CONCLUSIONS

Since patients with high microbial load had a worse outcome, quantitative cultures from DFUs can identify patients who would benefit from antibiotic therapy.

Cigarette Smoking and Peripheral Vascular Disease are Associated with Increasing Risk of ESKAPE Pathogen Infection in Diabetic Foot Ulcers

OBJECTIVE

Diabetic foot ulcers (DFUs) and ESKAPE pathogens have attracted attention globally, but the role of ESKAPE pathogens in diabetic foot infection is not well described. The purpose of this study was to evaluate the clinical features, antimicrobial resistance, and risk factors for ESKAPE infection in patients with DFUs.

METHODS

A retrospective study was conducted on 180 patients with diabetic foot infection admitted to The Affiliated Hospital of Southwest Medical University (Luzhou, China), from January 2017 to April 2021. Antimicrobial susceptibilities of all isolates were determined. Multivariate logistic regression analysis was performed to analyze the independent risk factors for ESKAPE infection, multidrug-resistant (MDR)-ESKAPE infection, MDR-pathogen infection, and severe group in patients with DFUs.

RESULTS

A total of 206 isolates were collected, of which 42.2% were ESKAPE pathogens. The independent risk factors for ESKAPE infection were cigarette smoking (OR = 1.958; 95% CI, 1.015-3.777) and peripheral vascular disease (OR = 2.096; 95% CI, 1.100-3.992), while alcohol consumption (OR = 2.172; 95% CI, 1.104-4.272) was the independent risk factor for MDR-pathogen infection. Additionally, the independent risk factors for severe DFU group were invasive treatment (OR = 326.642; 95% CI, 76.644-1392.08), the duration of systemic antibiotic treatment (OR = 0.918; 95% CI, 0.849-0.992), and length of hospital stay (OR = 1.145; 95% CI, 1.043-1.256). No independent risk factors for MDR-ESKAPE infection were found.

CONCLUSION

Our data established the microbiological features of ESKAPE pathogens and clinical manifestations of diabetic foot infection, and provide support for monitoring and management of ESKAPE infection in patients with DFUs in southwest China.

Diabetic foot infection caused by bacteria of the Burkholderia cepacia complex: report of an unusual case and a scoping literature review

Burkholderia cepacia complex (BCC) is group of widespread gram-negative bacillus organized in over 20 phylogenetically distinct bacterial species. According to previous studies, BCC species pathogens are widely reported in patients with cystic fibrosis (CF), but not in individuals with diabetes mellitus (DM). In this case report, a 42-year-old male patient with DM and a foot infection caused by BCC is presented. The patient was hospitalized after antibiotic treatment failure and improved after two surgical debridement procedures and a high-dose extended infusion (EI) of meropenem. The team of vascular surgeons and the infectious disease specialists worked fervently to solve the case. Finally, a scoping review was conducted to map BCC infections in patients with DM.

Impact of dedicated infectious disease teamwork on the treatment and prognosis of patients with diabetic foot infection

OBJECTIVE

The aim was to develop and evaluate the impact of a new model in which the infectious disease (ID) physician and pharmacist work together to treat diabetic foot infections (DFIs).

METHODS

A quasi-experimental before-after study was conducted. The medical charts of inpatients with DFI admitted between April 1, 2017 and March 31, 2018 were reviewed retrospectively (control group, n = 30). Inpatients diagnosed with DFI between April 1, 2018 and March 31, 2019 were enrolled prospectively as the intervention group and received treatment through dedicated ID teamwork (intervention group, n = 35).

RESULTS

The distribution of infection severity and levels of metabolic criteria were similar in the two groups. Compared with the control group, the intervention group received adequate initial empirical treatment more frequently (96.8% vs 43.5%, p < 0.001) and had a shorter median duration of fever (1 day vs 7.5 days, p < 0.001). Rates of healing and relapse within 6 months were similar in the two groups, although the intervention group showed more sites of osteomyelitis (p = 0.036) and a higher percentage of polymicrobial infections (48.6% vs 10.0%, p = 0.001).

CONCLUSION

The early and full participation of ID physicians and pharmacists in the treatment of DFI facilitated targeted antimicrobial treatment and improved patient outcomes.