Wound Dressing with Ionic Silver Kills Early to Prevent the Spread of Infection

January 3, 2012

By Phil Bowler, MPhil, BSc, FIBMS

"Superbug" bacteria are an ever-increasing threat to public health and are among the most difficult to treat. Many have built up a resistance to at least one type of antibiotic and often have the ability to spread readily throughout the environment. These traits contribute to the increasing number of patients that acquire superbugs. In just one example, a recent study showed the number of people diagnosed with community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) rose from 24 cases per 100,000 people in 2000 to 164 per 100,000 in 2005.

Patients may acquire superbugs during hospital stays and following surgery, trauma, disease or other causes. Associated wounds are susceptible to contamination and possible infection with superbugs. Dressings that include an antiseptic agent such as ionic silver and interact closely with the wound environment can help to kill bacteria or create an effective barrier to minimize spread.

The Antiseptic Agent as a Comprehensive Superbug Killer
Antiseptic agents such as ionic silver have been proven effective in killing a broad spectrum of microorganisms. In some situations, this can be advantageous over treatment with antibiotics, which are often effective in combating only a narrow spectrum of bacteria. Some antiseptics have been shown to be effective against antibiotic-resistant bacteria. Additionally, resistance to antiseptics is less likely to occur than resistance to antibiotics because their mechanism of action (MOA) often targets multiple bacterial sites. As a result, bacteria have more difficulty in anticipating and defending against an antiseptic attack compared with antibiotics that tend to have very specific target sites.

Not All Wound Dressings Are the Same: Choosing the Most Effective Antiseptic Dressing
All wounds are unique in their size, depth, topography, etc. In order to maximize effectiveness, an antimicrobial dressing should ideally conform to the wound bed, maximizing exposure of the antimicrobial agent to colonizing bacteria at the wound surface. A wound dressing with an antiseptic agent needs to fill the entire wound cavity and effectively manage exudate. Some dressings, such as gauze and alginates, allow bacteria to move through the dressing matrix. Hydrofiber® Technology* dressings form a cohesive gel following hydration and subsequently trap exudate and bacteria within the dressing matrix. However, Hydrofiber® Technology dressings may be more effective in minimizing opportunity for infection than dressings such as alginates by taking bacteria away from the wound and locking them within the dressing matrix.

Proven Effectiveness of a Hydrofiber® Technology Wound Dressing with Ionic Silver
In order to test the ability of a wound dressing to kill superbugs, researchers at ConvaTec recently conducted a stringent in vitro study to test the ability of AQUACEL® Ag* wound dressing to kill A. baumannii, C. difficile, CA-MRSA and ESBL-producing bacteria. Bacteria were inoculated into a simulated wound fluid and dressing samples were then saturated with this fluid. The test was continued for seven days, during which time samples of the fluid from around the dressing were taken to count viable bacteria. All test models were re-inoculated with a fresh culture of the same bacteria after 72 hours and continually monitored for bacteria survival.

AQUACEL® Ag wound dressing was shown to kill each of the four types of superbugs within the seven-day test period. The dressing killed ESBL-producing bacteria and A. baumannii quickly and consistently, with an approximate 100,000-fold reduction of all pathogens within 24 hours. The rate of kill for C. difficile was equally rapid, with an approximate 100,000-fold reduction of all bacteria after four hours. AQUACEL® Ag wound dressing was also successful in killing CA-MRSA bacteria with a 100-fold reduction in bacterial population within 48 hours and no bacteria detected by day seven.

The results of the study were recently presented at the 24th annual Symposium on Advanced Wound Care and Would Health Society (SAWC/WHS) in Dallas. The study adds to the growing evidence that wound dressings with antiseptic agents such as AQUACEL® Ag wound dressing can be an effective option for managing wounds to prevent or combat colonization with superbug bacteria. They can be used in conjunction with antibiotics or by themselves to control the bioburden and help immune cells to resolve an infection.
*Hydrofiber and AQUACEL Ag are registered trademarks of ConvaTec Inc.

Phil Bowler, MPhil, BSc, FIBMS, is director of infection prevention in the research and development department at ConvaTec Wound Therapeutics.