Lazaro-Martinez J et al recently evaluated the clinical and microbiological efficacy of silver foam dressings in the management of diabetic foot ulcers. They conducted a single-centre; prospective, open, noncontrolled study involving 21 outpatients with diabetic foot ulcers with mild infection.
All patients received standard of care for their wounds and a silver foam dressing with silicone adhesive was applied twice per week for wound management during a six-week treatment period. Soft tissue punch biopsies were taken every second week for qualitative and quantitative microbiological analysis.
Wounds were assessed at patient admission, and wound bed tissue was evaluated for presence, quality, and consistency of granulation tissue.
The study demonstrated that the use of a silver foam dressing with silicone adhesive has a clinical and microbiological efficacy in a case series of patients with DFUs. The main arguments against using topical antiseptics are the lack of adequate proof of efficacy and residual concerns about their potential toxicity to healing wounds. Regarding the clinical effectiveness, in our study population wound scores improved significantly, from a mean score of 3.9 ±1.6 points at inclusion to 6.1 ± 1.3 points at the end of the study (n = 19, P <.001).
Furthermore, we observed a significant decrease in exudate levels (38.8% of patients with high exudate levels at inclusion vs 5% at the end of the study, P = .0031) and in the mean ulcer size (2.27 cm2 at inclusion vs 0.99 cm2 at the end of the study, P = .001).
The stand-out feature of this study is that patients in their study received systemic antibiotics and our patients did not receive systemic antibiotic treatment during the study. The authors consider that the more positive effects of a silver dressing on overall wound condition for the patients initially prescribed antibiotics might be expected from use of a dressing, which absorbs and holds wound exudate.
The capacity to absorb, retain, and kill bacteria in infected wound fluid in the silver dressing may work in synergy with systemic antibiotics, which may not always reach microorganisms on the wound surface. In this study, patients did not receive systemic antibiotic treatment because the authors also analysed the microbiological effects of the silver dressing, and the systemic antibiotic treatment could have altered the microbiological results.
They observed that use of the silver dressing resulted in significant decreases at week six (P =.0148) in the bioburden of classically considered DFU pathogenic organisms. These results demonstrate efficacy of the silver dressing against several common wound pathogens in DFUs, and in this sense, this dressing may also prove helpful with the increasing problem of multidrug-resistant microorganisms that are untreatable with most systemic agents.
Although mechanical debridement before sampling should reduce, if not eliminate, the biofilm formed, the authors assumed that, under the assumption that most of DFUs presented in our study exhibited biofilms, the dressing was also active against bacteria embedded in biofilms. However, this should be specifically assessed in a future study since we did not perform a direct measure of biofilm occurrence.
On the other hand, the treatment with silver dressing contained the basal bioburden of DFUs in all patients who completed the study period irrespective of the clinical evolution during the follow-up (0.0 and 0.5 Log drop for patients with favourable and unfavourable clinical outcome, respectively). We know that the healing in DFUs will occur due to
- Adequate arterial inflow
- Appropriate control of infection
- Off-loading of the site of wound and immediate surrounding area is satisfied.
In this regard, one of the patients with unfavourable clinical evolution developed critical limb ischaemia and required a revascularisation treatment and another patient required surgical treatment due to diabetic foot osteomyelitis.
In the study population, two patients were excluded due to the presence of cellulitis during the treatment period because they requested systemic antibiotic treatment. It is uncertain whether use of an antimicrobial dressing affects the risk of adverse events compared with use of a nonantimicrobial dressing over a medium-term observation period in patients with DFU.
Regarding the potential toxicity of silver dressing to healing wounds, we know that the amount of silver release can be controlled by various means, most notably by increasing the surface of the incorporated silver preparation. Nanocrystalline silver dressings have been shown to release high amounts of silver ions over a short period of time and this could be associated with significant cytotoxicity.
Ziegler et al and Dong et al have reported that low-silver–releasing ointment dressing has less toxicity than other dressings surrounding wound tissues. The silver dressing used in the present study has a sustained silver release profile up to seven days in the presence of exudate. A similar sustained silver-release dressing has shown positive clinical results in non-healing wounds with signs of infection in several comparative clinical studies.
Currently, the balance between antimicrobial activity and cellular toxicity remains a challenge for developing new products, which may interfere less with normal wound healing processes. Given that unlike antimicrobials the resistance to antiseptics containing silver is rare and sporadic, the authors think that the balance between the benefit, that is, reduction of pathogenic bacterial load and prevention of the emergence of resistant organisms, and the risk for adverse effects or toxicity on the patient is favourable to the use of this silver dressing.
The authors conclude that the use of a silver foam dressing with silicone adhesive significantly reduced the pathogenic bacterial load and markedly improved the clinical outcome in patients with diabetic foot ulcer with mild infection over a six-week treatment period.