New in vitro study results show that wound dressing with ionic silver kills strains of highly-resistant bacteria

Apr 16 2011

ConvaTec, a world-leading developer and marketer of innovative medical technologies for community and hospital care, today announced new in vitro study results showing that a wound dressing containing ionic silver is able to kill several strains of highly-resistant bacteria, commonly referred to as 'superbugs.' The study showed that bacteria found beneath the dressing died within 48 hours. The study results were presented at the 24th Annual Symposium on Advanced Wound Care and Wound Healing Society (SAWC/WHS) in Dallas, Texas.

In the in vitro study, a simulated wound fluid (serum and peptone water) model was designed to measure antimicrobial activity over a seven-day wear time. A sample of the silver-containing sodium carboxymethyl cellulose wound dressing was aseptically transferred to the simulated wound fluid containing 1x10^6 cfu/ml of a wound pathogen (A. baumannii, C. difficile, CA-MRSA, or ESBL-producing bacteria). Following incubation, total viable counts (TVCs) were performed on each test model using a pour plate method. TVCs were performed on each model at four, 24, 48, 72, and 96 hours, and at seven days. All models were re-inoculated with a fresh challenge of the same bacteria at 72 hours.

Bacteria from external sources such as the surrounding skin, gut and mouth are often found in wounds associated with surgery, trauma, disease or other causes. Any wound, especially one that does not heal quickly or at all, presents an opportunity for bacterial colonization and difficult-to-treat infections. An increasing prevalence of bacteria with enhanced virulence that are resistant to antibiotics is becoming a major concern for treating clinicians and hospitals. To reduce the risk of infection, many wound dressings are designed to conform well to a wound's unique topography to position an antimicrobial agent to be in contact with threatening bacteria.  

In the study, bacteria samples were covered with silver-containing sodium carboxymethyl cellulose wound dressing. The dressing was shown to be effective against emerging pathogens over a seven-day test period, including against re-inoculation. 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 rapid, with an approximate 100,000-fold reduction of all bacteria after four hours. The potency of silver-containing sodium carboxymethyl cellulose wound dressing against CA-MRSA was effective with a 100-fold reduction in bacterial population within 48 hours and no bacteria detected by day seven.