Silver Antimicrobial Dressings in Wound Management: A Comparison of Antibacterial, Physical, and Chemical Characteristics

David Parsons, PhD; Philip G. Bowler, MPhil; Viv Myles, MSc; Samantha Jones, BSc

Disclosures

Wounds. 2005;17(8):222-232. 

In This Article

Abstract and Introduction

Abstract

Silver-containing dressings are widely used to assist with management of infected wounds and those at risk of infection. However, such dressings have varied responses in clinical use due to technological differences in the nature of their silver content and release and in properties of the dressings themselves. This study examines the relationship between silver content, rate of silver release, and antibacterial activity in a simulated wound fluid model against Staphylococcus aureus and Pseudomonas aeruginosa. The study also looks at other important measures for the clinical performance of dressings including fluid-handling properties and dressing pH. Seven proprietary silver-containing dressings (AQUACEL® Ag [Hydrofiber®; "nonwoven A"], Acticoat™ Absorbent [alginate; "nonwoven B"], SILVERCEL™ [alginate-carboxymethylcellulose nylon blended fibers; "nonwoven C"], Contreet® Foam [nonadhesive; "foam A"], PolyMem® Silver ["foam B"], Urgotul® S.Ag ["gauze"], and SilvaSorb® ["hydrogel"]) were assessed. No direct correlation between silver content, silver release, and antibacterial activity was found. Dressings with the highest silver content were nonwoven B and nonwoven C, while the lowest levels were found in nonwoven A and hydrogel. Nonwoven A, gauze, and nonwoven B were most effective against S aureus and P aeruginosa; however, their silver release rates differed widely. Free fluid absorption was greatest for the 2 foam dressings and least for gauze. However, nonwoven A and nonwoven B showed the best fluid retention under conditions of compression, while nonwoven A demonstrated the lowest level of capillary wicking. Dressing choice is a vital part of the successful management of infected wounds and those wounds at risk for infection. This study suggests that dressing selection should be based on the overall properties of the dressing clinically relevant to the wound type and condition.

Introduction

Critical colonization and infection of wounds present a dual problem for clinicians. First, there is the possibility of delayed wound healing, particularly in the presence of a compromised immune system or where the wound is grossly contaminated or poorly perfused.[1] Second, colonized and infected wounds are a potential source for cross-infection -- a particular concern as the spread of antibiotic-resistant species continues. For patients, an infected wound can have additional consequences including increased pain and discomfort, a delay in return to normal activities, and the possibility of a life-threatening illness. For healthcare providers, there are increases in treatment costs and nursing time to consider.[1,2]

Until recently, local wound infection has been a challenge with few management options. However, the advent of advanced wound dressings containing topical antimicrobial agents, such as silver, has provided a new approach to the control of wound pathogens.[3,4]

Silver has proven antimicrobial activity that includes antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE).[4] Its role as an antimicrobial agent is particularly attractive, as it has a broad spectrum of antimicrobial activity[5,6] with minimal toxicity toward mammalian cells at low concentrations[7] and has a less likely tendency than antibiotics to induce resistance due to its activity at multiple bacterial target sites.[8]

Topical creams or solutions containing silver (eg, silver sulfadiazine) have long been used as a mainstay of wound management in burn patients who are especially susceptible to infection.[1] However, disadvantages to their use include staining the skin and toxicity.[3] In addition, the need for frequent removal and reapplication of silver sulfadiazine due to the development of pseudoeschar is both time consuming for professionals and painful for patients.[3,9] A range of antimicrobial dressings containing silver either incorporated within or applied to the dressing are now available for clinical use.[10] This new class of dressings is designed to provide the antimicrobial activity of topical silver in a more convenient application. However, the dressings themselves differ considerably in the nature of their silver content and in their physical and chemical properties.

This study compares the in-vitro antibacterial activity of 7 such dressings against 2 common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. The correlation between silver content and/or silver release from each dressing and its antibacterial effect is examined, and factors relating to the provision of an optimal environment for wound healing are compared to provide a basis for an overall assessment of the clinically valuable properties of each dressing.

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