Silver In Wound Care: What You Should Know

Volume 23 - Issue 8 - August 2010
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Start Page: 36

Can Silver Be Effective In Removing Biofilm?

Increasing evidence indicates that topical ionized silver is effective for managing increased superficial bacterial burden in wounds to promote and stimulate healing of chronic ulcers. What about the role of silver with eradicating biofilm?

Recent studies have demonstrated that, in many chronic wounds, bacteria persist in adhesive, polymeric matrix biofilm communities.^3,6,10-12 Due to the properties of this extracellular polymeric substance and the ability of quorum sensing, these biofilms can induce chronic inflammation, which delays healing and causes the wound to become more resistant to antimicrobial therapy.^3,10-12 Attention in the wound care field is currently focusing on the role that biofilm plays in impairing healing of a chronic, nonhealing wound.

Another potential application that silver may provide is an ability to aid in the removal of biofilms, which have been implicated in persistent infections. Some in vitro tests of iodides, silver and hydrogen peroxide compounds show inhibition or disruption of biofilm.³ These findings have led to the suggestion that, in wounds that are properly treated but fail to heal, the physician should consider a topical silver product. Further studies are clearly needed to prove the use of silver is effective in eradicating biofilm from a chronic wound.

Author(s):

Rhonda Cornell, DPM

There has been a resurgence of silver dressings in wound care in recent years due to the antimicrobial activity of silver, its safety and a lack of resistance. Accordingly, this author discusses silver dressing selection, shares insights on nanocrystalline silver and assesses the current literature on silver in wound care.

Silver has inundated the field of wound care in the last decade in the form of different products and dressings. This resurgence can in part be attributed to the resistant strains of bacteria forming against commonly used antibiotics. We now know that even minute concentrations of silver have a bactericidal effect.¹ This has prompted the development of multiple silver-containing wound care products such as hydrogels, hydrofibers, foams, hydrocolloids, gauze and alginates.

The use of silver can play a major role in the infected, colonized and/or chronic wound. Silver is widely considered a broad-spectrum agent, which is effective against gram-positive organisms, gram-negative organisms and fungi as well as resistant strains of bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci.^1-5

Silver exerts its antimicrobial activity in the form of ionic silver (Ag+ ions). Silver facilitates the growth of proteins through a combination with chloride in tissues and by blocking the microbial respiratory chain system.⁴

The antimicrobial activity of Ag+ ions is generally attributed to four mechanisms.² Ionic silver:
• binds to the bacterial cell membrane, damaging it and interfering with various receptors;
• disrupts bacterial electron transport, impeding the production of adenosine triphosphate;
• impairs cell replication by binding to bacterial DNA; and
• triggers the intracellular formation of insoluble compounds with certain nucleotides, proteins and the amino acid histidine, making them unavailable as intracellular building blocks.

Importantly, silver can also decrease matrix metalloproteinases (MMPs) on the surface of wounds. This results in an increase in surface calcium, an enhancement of microbial effects and a decrease of inflammation within the wound. As we know, the proteolytic property of the MMPs is essential during wound healing to facilitate cell migration and remove debris.

However, excessive accumulation and activation of MMPs versus their inhibitors can compete with cell proliferation, angiogenesis and matrix proteins necessary for cell migration.⁶ Bacteria in chronic wounds also produce MMPs that may be responsible for the increasing tissue damage that can lead from critical colonization to infection. By reducing the number of bacteria and the associated inflammatory response it creates, a dressing containing nanocrystalline silver may facilitate wound healing.⁶

What Qualities Should You Look For In Silver Dressings?

There are four main categories of silver-containing dressings. The actions of these silver dressings include:

• releasing silver into the wound bed for antimicrobial action;
• absorbing wound exudate into the dressing fabric where the silver then exerts its bactericidal activity (into the dressing but not necessarily the wound);
• absorbing wound exudate and releasing silver into the wound bed for antimicrobial activity; and/or
• releasing silver sulfadiazine into the wound that cleaves in the presence of wound exudate and liberates the silver and sulfadiazine moiety.⁵