Clinical management of chronic wound infections: The battle against biofilm

Bacteria constitute the most abundant life form on earth, of which the majority exist in a protective biofilm state. Since the 1980s, we have learned much about the role of biofilm in human chronic infections, with associated global healthcare costs recently estimated at ~$386 billion. Chronic wound infection is a prominent biofilm-induced condition that is characterised by persistent inflammation and associated host tissue destruction, and clinical signs that are distinct from signs of acute wound infection. Biofilm also enables greater tolerance to antimicrobial agents in chronic wound infections compared with acute wound infections. Given the difficulty in eliminating wound biofilm, a multi-targeted strategy (namely biofilm-based wound care) involving debridement and antimicrobial therapies were introduced and have been practiced since the early 2000s. More recently, acknowledgement of the speed at which biofilm can develop and hence quickly interfere with wound healing has highlighted the need for an early anti-biofilm strategy to combat biofilm before it takes control and prevents wound healing. This strategy, referred to as wound hygiene, involves multiple tools in combination (debridement, cleansing, and antimicrobial dressings) to maximise success in biofilm removal and encourage wound healing. This review is intended to highlight the issues and challenges associated with biofilm-induced chronic infections, and specifically address the challenges in chronic wound management, and tools required to combat biofilm and encourage wound healing.

Enhanced exploration of the mode of action of a five-layer foam dressing: critical properties to support wound healing

OBJECTIVE

The aim of this in vitro experimental series was to explore the mode of action of a hydrocellular polyurethane foam dressing (HPFD) and how its advanced features support beneficial interactions with the wound bed to address common barriers to wound healing, thus supporting improved clinical outcomes.

METHOD

Multiple in vitro microbiological tests were performed, assessing prevention of bacterial ingress, surface removal of bacteria, bacterial sequestration and retention into the dressing in a clinically relevant environment. Odour molecule concentrations were measured using gas chromatography and further assays explored matrix metalloproteinase (MMP)-9 retention in the dressing using enzyme linked immunosorbent assay.

RESULTS

The HPFD demonstrated marked reductions in bioburden levels across multiple tests. These included prevention of bacterial ingress for seven days, removal of surface bacteria and absorption into the dressing. Further tests identified that most bacteria were sequestered into the hyperabsorbent layer (90.5% for Pseudomonas aeruginosa and 89.6% for meticillin-resistant Staphylococcus aureus). Moreover, the majority of bacteria (99.99% for both test organisms) were retained within the dressing, even upon compression. Additional tests demonstrated a marked reduction of odour molecules following incubation with HPFD and total retention of protease MMP-9 within the dressing.

CONCLUSIONS

Proactive management of the wound environment with an appropriate advanced wound dressing, such as the HPFD examined in these in vitro investigations, can not only help to minimise the barriers to healing, as observed across this test series by direct interaction with the wound bed, but may, as a result, provide an ideal environment for wound progression with minimal disturbance.

Clinical performance and safety of a debridement pad with abrasive and non-abrasive fibres

BACKGROUND

Debridement is key to removing devitalised tissue, debris and biofilm as part of wound-bed preparation. Unlike many other methods of debridement, mechanical debridement with a pad is effective enough to be used independently without an adjunctive method of debridement, while being more accessible than other standalone options.

OBJECTIVE

To explore the clinical performance and safety of a debridement pad with both abrasive and non-abrasive surfaces in daily clinical practice.

METHODS

This was a prospective, non-controlled, non-randomised, single-arm, open-label, multicentred observational evaluation. Inclusion criteria were wounds >4 cm2 covered with at least 30% debris, necrotic tissue or slough in patients aged ≥18 years. The treatment protocol comprised a single application of the debridement pad. The primary outcome measure was the amount of necrotic tissue, slough or debris in the wound bed. Secondary outcomes included the appearance of the wound bed, edges and periwound skin; self-reported pain scores; foreseeable negative impacts; and clinician satisfaction.

RESULTS

A total of 62 participants with a variety of wound types were included in the analysis. Most wounds (87%) had been present for over 3 months and had high or moderate exudate levels (90%). A significant reduction was observed in all three parameters: necrotic tissue (p=0.043), slough (p<0.001) and debris (p<0.001). Necrotic tissue, slough and debris showed mean relative reductions of 40%, 72% and 40%, respectively. Of participants, 84% did not experience an increase in pain during the debridement procedure.

CONCLUSION

This clinical real-world data shows the debridement pad to be an effective and well-tolerated device for debridement and wound bed preparation.

Positionspapier der Initiative Chronische Wunde (ICW) e. V. zur Nomenklatur des Débridements chronischer Wunden

Die heute in der Wundbehandlung verwendete Nomenklatur ist interdisziplinär und interprofessionell sehr unterschiedlich. Daher ist es ein Anliegen der Fachgesellschaft Initiative Chronische Wunde (ICW) e. V. bislang unklare Begriffe eindeutig und nachvollziehbar zu beschreiben. Von den Experten der ICW wurde daher in einem Konsensusverfahren als Débridement chronischer Wunden die Entfernung von anhaftendem, abgestorbenem Gewebe, Krusten oder Fremdkörpern aus Wunden bezeichnet. Hierfür gibt es verschiedene Therapieoptionen, die als autolytisches, biochirurgisches, mechanisches, osmotisches, proteolytisches/enzymatisches und technisches Débridement unterschieden werden können. Bei dem chirurgischen Débridement wird zudem zwischen meist ambulant durchführbaren scharfen Débridements wie beispielsweise kleineren chirurgischen Eingriffen und chirurgischen Débridements mit adäquater Anästhesie in einem Operationssaal differenziert. Als Wundspülung wird von der ICW die Entfernung von nicht haftenden Bestandteilen auf Wunden mit sterilen Lösungen bezeichnet.

Débridement und/oder Wundspülung sind oft der erste Schritt einer phasengerechten modernen Wundbehandlung. Mehrere Methoden eignen sich für die Anwendung einer kombinierten oder sukzessiven Therapie. Bei der Entscheidung, welche therapeutische Option hierbei zum Einsatz kommt, sollte eine Vielzahl individuell unterschiedlicher Faktoren in Abhängigkeit von den zu behandelnden Patienten, aber auch von den Therapeuten berücksichtigt werden. Die letztendliche individuelle Entscheidung für eine Methode sollte jeweils gemeinsam mit den Patienten getroffen und anschließend adäquat dokumentiert werden.

An audit to assess the impact of prescribing a monofilament fibre debridement pad for patients with unhealed wounds after six months

A monofilament fibre debridement pad has been found to be a rapid and effective mechanical method of removing dry skin, biofilm and debris from acute and chronic wounds with minimal patient discomfort. Evidence of its impact on prescribing and wound healing, however, has been more limited. The aim of this audit was to show evidence of the monofilament fibre debridement pad's impact on wound treatment costs through an analysis of NHS wound-care prescribing data in England. A dataset for 486 uniquely identified patients who had been newly prescribed the monofilament fibre debridement pad was obtained from the NHS Business Services Authority. All data were anonymised. Costs were identified for the six months before and six months after the month of first prescription of the monofilament fibre debridement pad. The total cost of wound-care prescribing fell by 14% or £101,723 in the six months after the intervention compared with the six months before. The average monthly expenditure per patient fell from £244 before the intervention to £209 (n=486) after. These results indicate that use of the monofilament fibre debridement pad could reduce prescribing costs and the use of antimicrobial and negative pressure therapies. Further research is warranted to investigate the clinical role of the monofilament fibre debridement pad in wound healing.

Mini-review: from in vitro to ex vivo studies: an overview of alternative methods for the study of medical biofilms

Microbial biofilms are a natural adaptation of microorganisms, typically composed of multiple microbial species, exhibiting complex community organization and cooperation. Biofilm dynamics and their complex architecture are challenging for basic analyses, including the number of viable cells, biomass accumulation, biofilm morphology, among others. The methods used to study biofilms range from in vitro techniques to complex in vivo models. However, animal welfare has become a major concern, not only in society, but also in the academic and scientific field. Thus, the pursuit for alternatives to in vivo biofilm analyses presenting characteristics that mimic in vivo conditions has become essential. In this context, the present review proposes to provide an overview of strategies to study biofilms of medical interest, with emphasis on alternatives that approximate experimental conditions to host-associated environments, such as the use of medical devices as substrata for biofilm formation, microcosm and ex vivo models.

Chronic wound biofilms: diagnosis and therapeutic strategies

OBJECTIVE

To review the diagnosis of chronic wound biofilms and discuss current treatment approaches.

DATA SOURCES

Articles included in this review were obtained from the following databases: Wanfang, China National Knowledge Infrastructure, PubMed, and the Web of Science. We focused on research published before August 2019 with keywords including chronic wound, biofilm, bacterial biofilms, and chronic wound infection.

STUDY SELECTION

Relevant articles were selected by carefully reading the titles and abstracts. Further, different diagnosis and clinical treatment methods for chronic wound biofilm were compared and summarized from the selected published articles.

RESULTS

Recent guidelines on medical biofilms stated that approaches such as the use of scanning electron microscopy and confocal laser scanning microscopy are the most reliable types of diagnostic techniques. Further, therapeutic strategies include debridement, negative pressure wound therapy, ultrasound, antibiotic, silver-containing dressing, hyperbaric oxygen therapy, and others.

CONCLUSION

This review provides the identification and management of biofilms, and it can be used as a tool by clinicians for a better understanding of biofilms and translating research to develop best clinical practices.

Enhanced Clearing of Wound-Related Pathogenic Bacterial Biofilms Using Protease-Functionalized Antibiotic Nanocarriers

Biofilms are prevalent in chronic wounds and once formed are very hard to remove, which is associated with poor outcomes and high mortality rates. Biofilms are comprised of surface-attached bacteria embedded in an extracellular polymeric substance (EPS) matrix, which confers increased antibiotic resistance and host immune evasion. Therefore, disruption of this matrix is essential to tackle the biofilm-embedded bacteria. Here, we propose a novel nanotechnology to do this, based on protease-functionalized nanogel carriers of antibiotics. Such active antibiotic nanocarriers, surface coated with the protease Alcalase 2.4 L FG, "digest" their way through the biofilm EPS matrix, reach the buried bacteria, and deliver a high dose of antibiotic directly on their cell walls, which overwhelms their defenses. We demonstrated their effectiveness against six wound biofilm-forming bacteria, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis, Klebsiella pneumoniae, Escherichia coli, and Enterococcus faecalis. We confirmed a 6-fold decrease in the biofilm mass and a substantial reduction in bacterial cell density using fluorescence, atomic force, and scanning electron microscopy. Additionally, we showed that co-treatments of ciprofloxacin and Alcalase-coated Carbopol nanogels led to a 3-log reduction in viable biofilm-forming cells when compared to ciprofloxacin treatments alone. Encapsulating an equivalent concentration of ciprofloxacin into the Alcalase-coated nanogel particles boosted their antibacterial effect much further, reducing the bacterial cell viability to below detectable amounts after 6 h of treatment. The Alcalase-coated nanogel particles were noncytotoxic to human adult keratinocyte cells (HaCaT), inducing a very low apoptotic response in these cells. Overall, we demonstrated that the Alcalase-coated nanogels loaded with a cationic antibiotic elicit very strong biofilm-clearing effects against wound-associated biofilm-forming pathogenic bacteria. This nanotechnology approach has the potential to become a very powerful treatment of chronically infected wounds with biofilm-forming bacteria.

A comparative study on the cellular viability and debridement efficiency of antimicrobial-based wound dressings

A concentrated surfactant gel containing polyhexamethylene biguanide (CSG-PHMB) (CSG: Plurogel) was evaluated for in vitro cell cytotoxicity using the direct contact, extraction, and cell insert assays, along with its ability to breakdown artificial wound eschar and slough, compared with other clinically available wound gels: a wound gel loaded with 0.13% benzalkonium chloride (BXG) and a highly viscous gel loaded with 0.1% polyhexamethylene biguanide (PXG). Following treatment with CSG-PHMB, BXG, and PXG at day 1, the viability of L929 and HDFa cells sharply decreased to lower than 20% of the culture media control in the direct contact assay; however, cell viability of L929 was 128.65 ± 1.41%, 99.90 ± 2.84%*, and 64.08 ± 5.99%* respectively; HDFa was 84.58 ± 10.41%, 19.54 ± 3.06%**, and 96.28 ± 33.67%, respectively, in the extraction assay. In the cell insert model, cell viability of L929 cells were 95.25 ± 0.96%, 47.49 ± 5.37%**, and 48.63 ± 7.00%**, respectively; HDFa cell viability were 92.80 ± 1.29%, 38.86 ± 4.28%**, and 49.90 ± 2.55%** (*: P < .01; **P < .001 compared with CSG-PHMB; cell viability of culture medium without treatment at day 1 was 100%). The cell extraction model on day 1 indicated that CSG-PHMB had higher viability of L929 cells compared with BXG. In addition, the cellular viability results indicated that CSG-PHMB gel exhibited lower cytotoxicity when compared with BXG and PXG in the cell insert model assay. Within the in vitro debridement model, CSG-PHMB exhibited an ability to potentially increase the loosening of the collagen matrix. The reason for this may be because of the concentrated surfactant found within the CSG-PHMB, which has the ability to lower the surface tension, aiding in the movements of fragments and debris in the fluorescent artificial wound eschar model (fAWE).

Biofilm management using monofilament fibre debridement technology: outcomes and clinician and patient satisfaction

Objective:

Best practice in wound bed preparation and biofilm-based wound management includes debridement to create a clean wound bed and to assist in minimising the redevelopment of biofilm. Biofilm that is not removed inhibits healing and redevelops if not prevented from doing so with topical antimicrobial agents. Monofilament fibre debriding technology (MFDT) is used for effective and rapid mechanical debridement of loose material, slough and biofilm. The objective of this evaluation was to determine the clinical effect and consequential levels of health professional and patient satisfaction with the results of a biofilm pathway that included MFDT to achieve debridement.

Methods:

This non-comparative, open label evaluation was conducted in static and non-static wounds that required debridement. MFDT was used to debride in a two-week evaluation of a biofilm pathway. Wounds were debrided three times in week one and twice in week two. Each debridement was followed by treatment with an antimicrobial dressing. Other care included secondary dressings and compression delivered according to local practice, guidelines and formularies. After the clinical evaluation, health professionals were invited to complete an online survey of the clinical outcomes and their satisfaction with the biofilm pathway.

Results:

There were 706 health professionals who provided answers to the survey questions. Wound types evaluated were leg ulcers (67.4%), pressure ulcers (10%), dehisced surgical wounds (1.7%), diabetic foot ulcers (7.4%) and other wounds (13.4%). Of the wounds, 9% were reported as non-static despite the eligibility criteria. Not all wounds followed the pathway. The most frequently-used antimicrobial was silver. Non-antimicrobial products used included all-in-one dressings, other secondary dressings and compression. There was a change in 77% of wounds overall after two weeks. Change was reported almost equally for both static and non-static wounds. Health professionals who did or did not follow the pathway were ‘completely satisfied’ or ‘satisfied’ with the overall clinical outcome 96% and 95%, respectively. Of the patients, 77% were ‘completely satisfied’ or ‘satisfied’ with healing after following the pathway, as reported by the treating health professional.

Conclusion:

The biofilm pathway that includes MFDT appears effective. Wounds managed on the pathway were debrided effectively and healing progressed to the satisfaction of both health professionals and patients.

Rapid debridement with monofilament fibre debridement technology: clinical outcomes and practitioner satisfaction

Objective:

To determine the clinical effect and consequential levels of health professionals and patient satisfaction with the results of debridement episodes of wounds with visible slough and/or scaly skin using monofilament fibre debridement technology.

Methods:

This was a non-comparative, open label evaluation conducted in static/non-healing acute and chronic wounds with visible slough and/or scaly skin that required debridement. Monofilament fibre debridement technology was applied in 1–2 sequential treatment episodes during normal clinical practice which followed local practice, guidelines or formularies. Following the clinical phase of the evaluation, health professionals were invited to complete an online survey of the clinical outcomes and their satisfaction with them.

Results:

Survey questions were answered by 1129 health professionals. Wounds managed using the monofilament fibre debridement technology during this evaluation included leg ulcers (63%), pressure ulcers (10%), dehisced surgical wounds (3%), diabetic foot ulcers (8%) and other wounds (13%). ‘Other’ wound types included acute dirty wounds, burns, cellulitis, psoriasis, diabetic amputation wounds, dry flaky skin, moisture wounds, trauma, varicose eczema. Of the wounds, 12% were reported as non-static. There was visible change in the wound and/or skin after first use of the monofilament fibre debridement technology in a high proportion of all wound types, and a further increase in the proportion of wounds with visible change after the second use. The visible difference was significant for both static and non-static wounds. User and patient satisfaction with all clinical outcomes were high, whether or not the user and patient had previous experience of monofilament fibre debridement technology.

Conclusion:

Monofilament fibre debridement technology provides rapid, visible and effective debridement of slough and scaly skin after one application and further visible improvement after two applications in static and non-static wounds. Health professionals and patients report high levels of satisfaction with outcomes following application of the monofilament fibre debridement technology.

In situ gelation of rhEGF-containing liquid crystalline precursor with good cargo stability and system mechanical properties: a novel delivery system for chronic wounds treatment

The objective of this study was to develop a novel delivery system for recombinant human epidermal growth factor (rhEGF) for chronic wound treatment. Such a delivery system should be of good cargo stability and system mechanical properties in order to guarantee a satisfactory wound-healing effect. rhEGF-containing lyotropic liquid crystalline precursors (rhEGF-LLCPs) with in situ gelation capability were considered as a promising candidate to achieve this aim. Various properties of the optimal formulations (rhEGF-LLCP1 and rhEGF-LLCP2) were characterized, including apparent viscosity, gelation time, in vitro release and phase behavior. The stability of rhEGF and system mechanical properties (i.e. mechanical rigidity and bioadhesive force) were verified. Interestingly, rhEGF-LLCP2 with a larger internal water channel diameter exhibited faster release rate in vitro and then better bioactivity in Balb/c 3T3 and HaCaT cell models. Moreover, rhEGF-LLCP2 showed distinct promotion effects on wound closure, inflammatory recovery and re-epithelization process in Sprague-Dawley rat models. In conclusion, rhEGF-LLCP emerged as a prospective candidate to preserve the stability and enhance the wound-healing effect of rhEGF, which might serve as a new delivery system for chronic wound therapies.

Efficacy and safety of a novel skin cleansing formulation versus chlorhexidine gluconate

BACKGROUND

This study evaluated whether a multi-ingredient surfactant colloidal silver technology was noninferior to a 4% chlorhexidine gluconate (CHG) antiseptic on immediate and persistent antimicrobial activity.

METHODS

The inguinal regions of 81 healthy adults were demarcated into 4 quadrants, and 3 were used for testing each product at baseline, 10 minutes, and 6 hours postapplication. The log of the number of colony forming units was obtained using a cylinder sampling technique. The 95% confidence interval of the test product to the control product with a margin of 0.65 was established as the upper limit of noninferiority.

RESULTS

A total of 81 individuals were enrolled. The colloidal silver product was found to be noninferior to 4% CHG at both 10 minutes and 6 hours postapplication.

CONCLUSIONS

The colloidal silver-based product was noninferior to the 4% CHG product at 10 minutes and 6 hours postapplication.