In vitro and in vivo evaluation of the antimicrobial effectiveness of non-medicated hydrophobic wound dressings

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.

Ceramic Dressings-A New Non-Pharmacological Therapeutic Option in the Management of Chronic Wounds?

A new ceramic dressing, free from active antimicrobial or pharmaceutical agents, uses physical binding mechanisms for its absorption capacities and bacterial-binding properties. The purpose of this study was to evaluate wound healing, bacterial-related retention, and diagnostic properties of ceramic dressings in patients with stagnated chronic wounds.

METHODS

In this monocentric, intra-individually controlled, prospective study, patients with conservatively treated refractory chronic wounds were enrolled. One week before the start of the application with ceramic dressing, it was ensured during a screening phase that chronic wounds showed less than a 10% reduction in wound size. During the 4-week ceramic dressing treatment wound size measurements, wound scoring, measurement of wound exudate amount, wound swabs, and ceramic dressing sonication (low-intensity ultrasound) were carried out. The sonication fluid of the removed ceramic dressing was used for analysis of bacterial retention and compared to wound swabs.

RESULTS

A total of 20 patients with a mean age of 64.6 years (±26.2) and 21 chronic wounds were included in this study. After a 4-week treatment, a significant reduction of median wound size from 1178 mm2 (range 104-6300) to 751.5 mm2 (range 16-4819) and better total wound scores were observed (p < 0.001). The sensitivity of bacteria detection was 90.7% in the sonication fluid from the ceramic dressings, while only 76.9% in the conventional wound swabs.

CONCLUSION

The new ceramic dressing seems to have a positive impact on wound healing in chronic wounds. Bacteria-binding characteristics of the investigated ceramic dressing, in combination with its debridement, absorption, and detoxification properties, could contribute to its healing abilities. Based on those results, the investigated ceramic dressing seems to be a promising new treatment option for chronic wounds without the use of any active antimicrobial or pharmacological agents. Moreover, ceramic dressings can also be considered for microbiological diagnostic purposes.

Fluid handling by foam wound dressings: From engineering theory to advanced laboratory performance evaluations

This article describes the contemporary bioengineering theory and practice of evaluating the fluid handling performance of foam-based dressings, with focus on the important and clinically relevant engineering structure-function relationships and on advanced laboratory testing methods for pre-clinical quantitative assessments of this common type of wound dressings. The effects of key wound dressing material-related and treatment-related physical factors on the absorbency and overall fluid handling of foam-based dressings are thoroughly and quantitively analysed. Discussions include exudate viscosity and temperature, action of mechanical forces and the dressing microstructure and associated interactions. Based on this comprehensive review, we propose a newly developed testing method, experimental metrics and clinical benchmarks that are clinically relevant and can set the standard for robust fluid handling performance evaluations. The purpose of this evaluative framework is to translate the physical characteristics and performance determinants of a foam dressing into achievable best clinical outcomes. These guiding principles are key to distinguishing desirable properties of a dressing that contribute to optimal performance in clinical settings.