Rapid detection of biofilm with modified alcian blue staining: In-vitro protocol improvement and validation with clinical cases

Association of biofilm and microbial metrics with healing rate in older adults with chronic venous leg ulcers

The presence of microbial biofilms in many human chronic wounds led to the hypothesis that biofilms delay healing of these wounds. We tested this hypothesis in a population of 117 older individuals with venous leg ulcers who were receiving standardised therapy, including frequent debridement. Debridement specimens were analysed for the amount of bacterial biomass by two independent methods: a microscopic approach that scored the relative size and number of bacterial aggregates, interpreted as a biofilm metric, and conventional enumeration by agar plating for viable bacteria. The plating protocol yielded three distinct values: the total viable bacterial count, bleach-tolerant bacteria, and the log reduction in viable bacteria upon bleach treatment. Wound healing rates over an 8-week observation period were calculated as the rate of decrease of the equivalent diameter of the wound. There was no statistically significant association between wound healing and the biofilm metric in any of the three analyses performed (p ≥0.15). In all three statistical tests, wound healing was associated with the log reduction caused by bleach treatment (p ≤0.004); wounds that harboured bacteria that were more bleach-susceptible healed more slowly. A refinement of the model of chronic wound infection pathogenesis is proposed in which dormant bacteria constitute a persistent nidus and outgrowth of metabolically active cells impairs healing. This model constitutes a new hypothesis as metabolic activity was not directly measured in this investigation.

Systematic review and meta-analysis of diagnostic test accuracy in chronic wound's microbiology

PURPOSE

This study aims to assess the diagnostic accuracy of non-culture-based methodologies for detecting microorganisms in chronic wounds.

METHODS

We systematically reviewed studies that evaluated the diagnostic accuracy of alternative tests in chronic wound samples, excluding studies focused on animal samples or unrelated conditions. The search encompassed PubMed, CINAHL, Scopus and Web of Science databases, employing the QUADAS-2 tool for risk of bias assessment. Our search included the PubMed, CINAHL, Scopus and Web of Science databases, and we assessed the risk of bias using the QUADAS-2 tool. A meta-analysis was conducted on polymerase chain reaction (PCR) and colorimetric methods to determine sensitivity, specificity, diagnostic odds ratio, and summary receiver-operating characteristic (sROC) curves using a random-effects model. For methods not suitable for quantitative synthesis, a narrative synthesis was performed.

RESULTS

Nineteen studies involving various types of chronic wounds were analysed, revealing diverse diagnostic methods including fluorescence, PCR, colorimetry, voltammetry, electronic nose, biosensors, enzymatic methods, staining and microscopy. Combining fluorescence with clinical signs and symptoms (CSS) versus culture showed significant accuracy. Colorimetry demonstrated low sensitivity but high specificity, with a diagnostic odds ratio of 6.3. PCR generally exhibited good accuracy, although significant heterogeneity was noted, even in subgroup analyses.

CONCLUSIONS

This study identified a broad spectrum of diagnostic approaches, highlighting the superior diagnostic accuracy achieved when microbiological analysis is combined with clinical assessments. However, the heterogeneity and methodological variations across studies present challenges in meta-analysis. Future research should aim for standardized and homogeneous study designs to enhance the assessment of diagnostic accuracy for alternative methods.

Challenges in Biofilm Identification in Diabetic Foot Infections: Review of Literature

Foot ulcerations are one of the most common complications of diabetes and one of the major initial causes of amputations. The formation of biofilms on wounds significantly contributes to infections and delayed healing. While existing methods for identifying these biofilms have limitations, there is a need for a convenient tool for its clinical application. This literature review aimed to address the problem with current clinical biofilm identification in wound care and a proposal for biofilm-detection-based wound care in diabetic foot ulcer patients. Identifying biofilms is particularly vital due to the absence of typical signs of infection in DFUs. However, current approaches, although effective, often prove invasive and technically intricate. The wound blotting technique, involving attaching a nitrocellulose membrane and subsequent staining, presents an alternative that is swift and non-invasive. Research highlights the applicability of wound blotting with alcian blue staining in clinical scenarios, consistently producing sensitive outcomes. By addressing the critical need for early biofilm detection, wound blotting holds promise for enhancing DFU management and contributing to strategies aimed at preventing amputations.

DNM3OS/miR-127-5p/CDH11, activates Wnt3a/β-catenin/LEF-1 pathway to form a positive feedback and aggravate spine facet joint osteoarthritis

Spinal facet joint osteoarthritis (FJOA) is an OA disease with pathogenesis and progression uncovered. Our present study was performed to elucidate the role of DNM3OS on spinal FJOA. In this study, spine facet joint tissue of patients were collected. In vitro and in vivo models were constructed with SW1353 cells and rats. Hematoxylin and eosin (HE) staining, Safranin O-fast Green, Alcian blue staining, and Tolueine blue O (TBO) staining were employed for histology analyses. Quantitative PCR, western blotting, and Immunofluorescence were performed to evaluate the expression of genes. The levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assay analysis. Cell Counting Kit-8 and flow cytometry were used for cell activity and apoptosis evaluation. The targeting sites between microRNA (miR)-127-5p and cadherin 11 (CDH11) were predicted TargetScan and miRbase database and confirmed by Dual-luciferase reporter assays. CHIP and EMS assay were employed to confirm the binding of LEF1and DNM3OS promoter. Our results showed that DNM3OS was found to upregulated, while miR-127-5p was downregulated in severe FJOA patients and inflammation-induced chondrosarcoma SW1353 cells. DNM3OS reduced cell activity, induced cell apoptosis and extracellular matrix (ECM) degradation by sponging miR-127-5p in vitro. miR-127-5p targeted CDH11 and inhibited wnt3a/β-catenin pathway to regulate OA in vitro. LEF1 promoted DNM3OS transcription to form a positively feedback in activated wnt3a/β-catenin pathway. In vivo rat model also confirmed that DNM3OS aggravated FJOA. In summary, DNM3OS/miR-127-5p/CDH11 enhanced Wnt3a/β-Catenin/LEF-1 pathway to form a positive feedback and aggravate spinal FJOA.

Research hotspot and trend of chronic wounds: A bibliometric analysis from 2013 to 2022

Chronic wounds have been confirmed as a vital health problem facing people in the global population aging process. While significant progress has been achieved in the study of chronic wounds, the treatment effect should be further improved. The number of publications regarding chronic wounds has been rising rapidly. In this study, bibliometric analysis was conducted to explore the hotspots and trends in the research on chronic wounds. All relevant studies on chronic wounds between 2013 and 2022 were collected from the PubMed database of the Web of Science (WOS) and the National Center for Biotechnology Information (NCBI). The data were processed and visualised using a series of software. On that basis, more insights can be gained into hotspots and trends of this research field. Wound Repair and Regeneration has the highest academic achievement in the field of chronic wound research. The United States has been confirmed as the most productive country, and the University of California System ranks high among other institutions. Augustin, M. is the author of the most published study, and Frykberg, RG et al. published the most cited study. Furthermore, the hotspots of wound research over the last decade were identified (e.g., bandages, infection and biofilms, pathophysiology and therapy). This study will help researchers gain insights into chronic wound research's hotspots and trends accurately and quickly. Moreover, the exploration of bacterial biofilm and the pathophysiological mechanism of the chronic wound will lay a solid foundation and clear direction for treating chronic wounds.

Non-invasive biomedical sensors for early detection and monitoring of bacterial biofilm growth at the point of care

Bacterial infections have long been a serious global health issue. Biofilm formation complicates matters even more. The biofilm's extracellular polymeric substances (EPSs) matrix protects bacteria from the host's immune responses, yielding strong adhesion and drug resistance as the biofilm matures. Early bacterial biofilm detection and bacterial biofilm growth monitoring are crucial to treating biofilm-associated infections. Current detection methods are highly sensitive but not portable, are time-consuming, and require expensive equipment and complex operating procedures, limiting their use at the point of care. Therefore, there is an urgent need to develop affordable, on-body, and non-invasive biomedical sensors to continuously monitor and detect early biofilm growth at the point of care through personalized telemedicine. Herein, recent advances in developing non-invasive biomedical sensors for early detection and monitoring bacterial biofilm growth are comprehensively reviewed. First, biofilm's life cycle and its impact on the human body, such as biofilm-associated disease and infected medical devices, are introduced together with the challenges of biofilm treatment. Then, the current methods used in clinical and laboratory settings for biofilm detection and their challenges are discussed. Next, the current state of non-invasive sensors for direct and indirect detection of bacterial biofilms are summarized and highlighted with the detection parameters and their design details. Finally, commercially available products, challenges of current devices, and the further trend in biofilm detection sensors are discussed.

Sampling the skin surface chemistry for diagnosis and prognosis

Skin and wound blotting are non‐invasive techniques used to sample the skin and wound surface chemistry, whereby a nitrocellulose membrane is applied to an intact or broken cutaneous surface to detect biomarkers. However, there has been no comprehensive review of the evidence for the techniques used and data obtained to date. The primary aim of this study was to review the utilities of surface blotting for the diagnosis and prognosis of physiological, pre‐disease, and pathological states. The secondary aim was to summarise the procedural steps. A systematic literature search was conducted on 9 July 2021 using Medline, Embase, and Google Scholar databases. Investigators used McMaster's Critical Review Form for Quantitative Studies to assess quality, then performed a narrative synthesis reporting according to Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Twenty‐five studies were reviewed. Eighteen studies were of good quality, and seven were of moderate quality. These studies conducted skin and wound blotting on 176 animals and 1546 humans. Studies reported physiological and pathological states for diagnosis and prediction of conditions, including skin tears, wound healing, biofilm detection, and skin barrier function. The four steps for blotting are surface preparation, blot preparation, application and removal of blot, and analysis. This review demonstrates that blotting can determine the skin and wound surface chemistry using a versatile and reproducible technique. However, future research is needed to validate the technique and skin biomarkers identified.

Point-of-Care Wound Blotting with Alcian Blue Grading versus Fluorescence Imaging for Biofilm Detection and Predicting 90-Day Healing Outcomes

Biofilm infection has been identified as a crucial factor of the pathogenesis of chronic wound, but wound biofilm diagnosis remains as an unmet clinical need. We previously proposed a modified wound blotting technique using Alcian blue staining for biofilm detection that was characterized as being non-invasive, time-saving, non-expansive, and informative for biofilm distribution. In this study, we adapted a novel Alcian blue grading method as the severity of biofilm infection for the wound blotting technique and compared its biofilm detection efficacy with MolecuLight i:X- a point-of-care florescence imaging device to detect bacteria and biofilm in wounds. Moreover, their predictive value of complete wound healing at 90 days was analyzed. When validated with wound culture results in the 53 enrolled subjects with chronic wounds, the modified wound blotting method showed a strong association with wound culture, while MolecuLight i:X only exhibited a weak association. In predicting 90-day wound outcomes, the modified wound blotting method showed a strong association (Kendall’s tau value = 0.563, p < 0.001), and the wound culture showed a moderate association (Spearman’s rho = 0.535, p < 0.001), but MolecuLight i:X exhibited no significant association (p = 0.184). In this study, modified wound blotting with the Alcian blue grading method showed superior value to MolecuLight i:X both in biofilm detection and predictive validity in 90-day wound-healing outcomes.

Novel Diagnostic Technologies and Therapeutic Approaches Targeting Chronic Wound Biofilms and Microbiota

Purpose of Review

To provide an up-to-date overview of recent developments in diagnostic methods and therapeutic approaches for chronic wound biofilms and pathogenic microbiota.

Recent Findings

Biofilm infections are one of the major contributors to impaired wound healing in chronic wounds, including diabetic foot ulcers, venous leg ulcers, pressure ulcers, and nonhealing surgical wounds. As an organized microenvironment commonly including multiple microbial species, biofilms develop and persist through methods that allow evasion from host immune response and antimicrobial treatments. Suppression and reduction of biofilm infection have been demonstrated to improve wound healing outcomes. However, chronic wound biofilms are a challenge to treat due to limited methods for accurate, accessible clinical identification and the biofilm's protective properties against therapeutic agents. Here we review recent approaches towards visual markers for less invasive, enhanced biofilm detection in the clinical setting. We outline progress in wound care treatments including investigation of their antibiofilm effects, such as with hydrosurgical and ultrasound debridement, negative pressure wound therapy with instillation, antimicrobial peptides, nanoparticles and nanocarriers, electroceutical dressings, and phage therapy.

Summary

Current evidence for biofilm-targeted treatments has been primarily conducted in preclinical studies, with limited clinical investigation for many therapies. Improved identification, monitoring, and treatment of biofilms require expansion of point-of-care visualization methods and increased evaluation of antibiofilm therapies in robust clinical trials.

Chronic wounds: Treatment consensus

The Wound Healing Foundation (WHF) recognised a need for an unbiased consensus on the best treatment of chronic wounds. A panel of 13 experts were invited to a virtual meeting which took place on 27 March 2021. The proceedings were organised in the sub-sections diagnosis, debridement, infection control, dressings, grafting, pain management, oxygen treatment, outcomes and future needs. Eighty percent or better concurrence among the panellists was considered a consensus. A large number of critical questions were discussed and agreed upon. Important takeaways included that wound care needs to be simplified to a point that it can be delivered by the patient or the patient's family. Another one was that telemonitoring, which has proved very useful during the COVID-19 pandemic, can help reduce the frequency of interventions by a visiting nurse or a wound care center. Defining patient expectations is critical to designing a successful treatment. Patient outcomes might include wound specific outcomes such as time to heal, wound size reduction, as well as improvement in quality of life. For those patients with expectations of healing, an aggressive approach to achieve that goal is recommended. When healing is not an expectation, such as in patients receiving palliative wound care, outcomes might include pain reduction, exudate management, odour management and/or other quality of life benefits to wound care.

Micrococcal Nuclease stimulates Staphylococcus aureus Biofilm Formation in a Murine Implant Infection Model

Advancements in contemporary medicine have led to an increasing life expectancy which has broadened the application of biomaterial implants. As each implant procedure has an innate risk of infection, the number of biomaterial-associated infections keeps rising. Staphylococcus aureus causes 34% of such infections and is known as a potent biofilm producer. By secreting micrococcal nuclease S. aureus is able to escape neutrophil extracellular traps by cleaving their DNA-backbone. Also, micrococcal nuclease potentially limits biofilm growth and adhesion by cleaving extracellular DNA, an important constituent of biofilms. This study aimed to evaluate the impact of micrococcal nuclease on infection persistence and biofilm formation in a murine biomaterial-associated infection-model with polyvinylidene-fluoride mesh implants inoculated with bioluminescent S. aureus or its isogenic micrococcal nuclease deficient mutant. Supported by results based on in-vivo bioluminescence imaging, ex-vivo colony forming unit counts, and histological analysis it was found that production of micrococcal nuclease enables S. aureus bacteria to evade the immune response around an implant resulting in a persistent infection. As a novel finding, histological analysis provided clear indications that the production of micrococcal nuclease stimulates S. aureus to form biofilms, the presence of which extended neutrophil extracellular trap formation up to 13 days after mesh implantation. Since micrococcal nuclease production appeared vital for the persistence of S. aureus biomaterial-associated infection, targeting its production could be a novel strategy in preventing biomaterial-associated infection.

An adaptable microreactor to investigate the influence of interfaces on Pseudomonas aeruginosa biofilm growth

Abstract

Biofilms are ubiquitous and notoriously difficult to eradicate and control, complicating human infections and industrial and agricultural biofouling. However, most of the study had used the biofilm model that attached to solid surface and developed in liquid submerged environments which generally have neglected the impact of interfaces. In our study, a reusable dual-chamber microreactor with interchangeable porous membranes was developed to establish multiple growth interfaces for biofilm culture and test. Protocol for culturing Pseudomonas aeruginosa (PAO1) on the air–liquid interface (ALI) and liquid–liquid interface (LLI) under static environmental conditions for 48 h was optimized using this novel device. This study shows that LLI model biofilms are more susceptible to physical disruption compared to ALI model biofilm. SEM images revealed a unique “dome-shaped” microcolonies morphological feature, which is more distinct on ALI biofilms than LLI. Furthermore, the study showed that ALI and LLI biofilms produced a similar amount of extracellular polymeric substances (EPS). As differences in biofilm structure and properties may lead to different outcomes when using the same eradication approaches, the antimicrobial effect of an antibiotic, ciprofloxacin (CIP), was chosen to test the susceptibility of a 48-h-old P. aeruginosa biofilms grown on ALI and LLI. Our results show that the minimum biofilm eradication concentration (MBEC) of 6-h CIP exposure for ALI and LLI biofilms is significantly different, which are 400 μg/mL and 200 μg/mL, respectively. These results highlight the importance of growth interface when developing more targeted biofilm management strategies, and our novel device provides a promising tool that enables manipulation of realistic biofilm growth.

Key points

• A novel dual-chamber microreactor device that enables the establishment of different interfaces for biofilm culture has been developed.

• ALI model biofilms and LLI model biofilms show differences in resistance to physical disruption and antibiotic susceptibility.