Reducing Wound Bioburden with Antimicrobial Dressings
Article originally featured on Health Europa
HEQ examines the role of dressings with antimicrobial properties in treating and preventing wound infection.
The increased prevalence of antimicrobial dressings in wound care can broadly be attributed to two key factors: firstly, advances in research and technology have enabled healthcare practitioners to rely in greater proportions on dressings which incorporate antibacterial agents, but – crucially – which do not damage healthy tissue, with some dressing types even accelerating the wound healing process. Secondly, growing concern throughout the health and care sectors over antibiotic resistance in infections has led to a greater demand for broad spectrum antiseptic and antibacterial agents, which typically carry a reduced risk of bacteria developing resistance.
The optimum antimicrobial dressing should have a number of key properties, including:
A broad spectrum of rapid, sustained antibacterial activities;
Bacteriocidal, meaning they actively kill bacteria, rather than bacteriostatic, which refers to agents which prevent bacteria from reproducing further without necessarily killing bacteria which are already present;
Non-irritant, non-toxic and suitable for use on broken skin;
Not arrested or slowed by wound exudate or other bodily fluids;
Able to reduce malodour stemming from infected tissue;
Cost effective; and
Stable and easy to store and apply.
To lessen the risk of unnecessary side effects and optimise the treatment pathway, antimicrobial dressings should be applied only in specific circumstances: to treat localised wound infections; to deliver localised treatment for systemic or spreading infection in tandem with systemic antibiotic treatment; and to prevent a wound from becoming infected in cases where the patient is at a heightened risk of infection.
Honey in dressings
Medical grade honey has a number of benefits in wound treatment: as it has both antimicrobial and anti-inflammatory properties, it can avert the risk of a wound becoming infected while reducing inflammation of the wound surface. It supports moist healing of wounds, which can reduce levels of scarring; and promotes the autolytic debridement of wounds, wherein the body’s own enzymes are activated to liquefy and slough necrotic tissue, in addition to controlling and preventing wound malodour. The NHS recommends honey-impregnated dressings as first line treatments within a primary care setting.
The British National Formulary (BNF), the UK’s primary pharmaceutical reference text, recommends that dressings containing honey as an active antibacterial should not be used in cases where the patient has an extreme sensitivity or allergy to either bee products or bee stings. The BNF also advises that, where honey-based dressings are used in the treatment of diabetic patients, the patient’s blood glucose levels should be monitored assiduously, due to the enhanced risk of sugars from the honey passing into the patient’s bloodstream.
Silver in dressings
Silver has long been recognised in both the health and food sectors for its antimicrobial properties, with the earliest recorded use of silver to stave off wound infection dating back to around 4000BCE; and the market for silver nanoparticles, a common component in wound dressings and more recently in food packaging, is projected to grow to around $3bn by 2024. In addition to acting as an effective antibacterial, silver acts as an anti-inflammatory on wounds which are already infected; current guidelines indicate that dressings containing silver should primarily be used in cases where infection symptoms are already present. Zinc can be used in tandem with silver as a wound treatment or dressing component to further accelerate the wound healing process: some evidence has suggested that the use of silver on its own may slow the healing process to some degree. Dressings containing silver may not be worn if the patient is undergoing a magnetic resonance imaging (MRI) scan.
Silver is a popular antibacterial additive for dressings and wound treatments such as creams and ointments, due to both the inability of microorganisms to develop a functional resistance to silver and its high efficiency level, with silver-infused dressings commonly containing one part silver per million or less. In order for its bacteriocidal properties to take effect, the silver must be delivered in the form of ions, or charged particles.
Within a wound dressing context, ionic silver nanocrystals are integrated into the material of fabric or foam dressings, offering controlled coverage of the wound surface. These dressings offer more intense levels of silver activity over a shorter period of time. Silver sulfadiazine, which combines silver ions with a sulphonamide antimicrobial agent for ease of delivery, is commonly administered in cream form, although silver sulfadiazine-based dressings are available; it has broad spectrum antibacterial properties, but ideally should not be deployed over large areas or for long periods of time, due to the associated risk of skin discoloration and, in some cases, the onset of blood disorders. Dressings and skin treatments containing silver sulfadiazine are contraindicated in neonatal and pregnant patients, as well as in patients with impaired kidney or liver function.
Iodine in dressings
Fabric dressings impregnated with povidone-iodine or cadexomer-iodine react when exposed to wound exudate, slowly releasing free iodine which acts as a broad spectrum antiseptic. Within certain parameters, therefore, iodine is particularly recommended in the treatment of wounds with high levels of exudate or slough. Chlorhexidine is indicated for patients with an allergy or sensitivity to iodine.
Povidone iodine is typically only recommended for dressing superficial injuries, as its antimicrobial properties are rapidly deactivated by prolonged contact with pus or wound exudate. When iodine is used to treat large wounds or over a prolonged period, there is an increased risk of systematic absorption of iodine into the bloodstream: for this reason, caution is particularly recommended in the use of iodine dressings in treating children, pregnant or breastfeeding women, and patients with thyroid disorders or renal conditions.
The projected ‘next generation’ of wound management is the development of smart dressings, which are equipped with a variety of integrated technological solutions including:
Fibre optic biomarker sensors capable of monitoring the wound healing process and detecting skin temperature spikes which may indicate the presence of infection;
Smartphone connectivity to enable the real time monitoring of biomarkers;
Ultraviolet (V) diodes connected to a temperature sensor, which activate a UV-sensitive antimicrobial hydrogel in the event of a temperature spike; and
Polymer nanofibre meshes which actively draw bacteria out of a wound.