Antimicrobial properties of wound dressings

Wound infections are a very common healthcare problem and can lead to significant mortality and morbidity. In the UK there are four classes of antimicrobial dressings, honey, silver, iodine and biguanides, available to treat infected wounds. The evidence to support the efficacy of these materials is often scarce, as they are classed as medical devices and as such are not required to undertake the rigorous clinical evaluations expected for medicinal products. This research was designed to investigate the antimicrobial properties of wound dressings and to determine if bacterial wound pathogens are more susceptible to a particular class of antimicrobial wound dressing. The primary aim of the research was to develop a novel wound dressing which could deliver a controlled release of an antimicrobial agent over a sustained period of time. The in vitro antimicrobial activity of 20 antimicrobial dressings were tested against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, bacteria commonly found in chronic wounds. Whilst most of the dressings demonstrated a degree of antimicrobial efficacy against all of the bacteria, their duration of antimicrobial action was limited. Only the silver dressings were shown to be effective for more than 48 hours. A new material was created by the addition of clay platelets to a composite containing polyvinyl alcohol [PVOH] and polyvinylpyrrolidine [PVP] containing 6wt% iodine. The material was effective against the test bacteria for at least 72 hours and was also able to eradicate in- vitro biofilms containing S. aureus and E. coli. The novel material formed a self-stratifying film and both sides of the material demonstrated different release characteristics. One side of the material was still effective against S. aureus after eight days continuous use. The new material has been shown to be significantly different to any of the commercial dressings tested. The unique two side release profile, absorbent wicking properties and the colour change indicator make this material different to any of the dressings currently available in the UK and provides a novel material for the treatment of infected wounds.