Selection of topical antimicrobials

After diagnosis of a wound infection, a topical antimicrobial will need to be selected. In this article, Professor Karen Ousey discusses the selection of these antimicrobials and how this should be linked to antimicrobial stewardship.

Lipsky’s paper for the Antimicrobial Stewardship in Wound Care, a Position Paper states that AMS includes avoiding prescribing antimicrobials when they’re not indicated, so when a wound is not clinically infected. It also states that although skin and soft tissue infections are amongst the most common ones for which antimicrobials are prescribed, there isn’t much published guidance for proven antimicrobial therapy for these infections. What is more concerning is that guidance could not be found for patients who had an infected wound, especially since these are managed on a daily basis.

When selecting a topical antimicrobial, a full patient assessment must be taken to identify the wound infection; this may include sending off swabs and cultures to be tested. When choosing the dressing itself, the optimum conditions to support rapid healing and manage the extent, pain and malodour of the wound, must be present.

During selection, consideration must be given to:

• Specificity and efficacy of the agent – choosing the most effective antimicrobial for the type of wound infection.

• Its cytotoxicity to human cells.

• Its potential to select resistant strains.

• Its allergenicity – use the patient history to see what they are allergic to.

• Frequency of dressing changes – do not use any slow-release formula for wounds that require frequent dressing changes. Application and removal of dressings should be done so that there is not skin-stripping, or this will cause extra pain.

• Wound size – you will need a dressing that covers the peri-wound areas and prevents any maceration.

• Wound location – dressings should be flexible. If the dressing is likely to fall off often due to its location, the patient should be made aware of this.

• Pain – dressings providing moist, non-adherent contact are least likely to cause pain when removed. Gauze has been associated with pain at dressing change.

• Patient preference – compliance will be improved if the dressing meets patients’ needs.

Only if the wound is clinically infected, should antibiotics be prescribed. Both therapies, the antibiotic and the antimicrobial dressing, should be reviewed regularly. The duration of therapy is usually for about one or two weeks for antibiotics for soft tissue and about six weeks for bone infection. You can look at the two-week challenge here, or regular assessment, to see whether the treatment and use of antimicrobials is actually having a positive effect.

A multidisciplinary team must be involved in selection: tissue viability nurses, infection prevention control teams, microbiologist, medical staff, pharmacists (and podiatrists – if the wound is situated in the lower limb, as they will be able to advise on offloading procedures). The patient must also be involved in the decision making, so that they are happy and knowledgeable about the treatment.

Types of antimicrobials

Antimicrobials are agents that either kill or inhibit the growth and division of micro-organisms. They include antibiotics (which act on specific cellular target sites), antiseptics, disinfectants and other agents (which act on multiple cellular target sites).

• Chlorhexidine

• Products containing iodine (cadexomer iodine and povidone iodine). Some research has shown reduced bacteria counts and improved healing with iodine.

• Products containing silver (silver sulfadiazine and silver-impregnated dressings). Particularly used with some burns and skin grafting as a prophylaxis to prevent infection.

Lipsky’s work in 2016 identified that microbiological investigations for a clinically uninfected wound are needed only when seeking evidence of colonisation. So if the patient isn’t feeling unwell and there’s no signs and symptoms of a clinical wound infection, there’s probably no need for antibiotics.

Now you’ve learnt about definition of a wound infection, signs and symptoms, identification, diagnosis, management and choosing a suitable topical antimicrobial, it is time to reflect. Go into clinical practice and look at what your own local guidance policies and procedures are that relate to AMS and management of wound infection. Make sure everyone in your team is aware of the importance of AMS in wound infections, either by checking that they already have the knowledge, or passing on your new knowledge. All care must be evidence- and research-based.

The patients may also need to be made aware of how to manage their wound infection; for example what to look for when they are home, how to keep everything sterile, and how to carry out proper handwashing. More patient leaflets may need to be developed in order to ensure these needs are met.

Please take a look at the articles in the see also section below. It is really important that all health care practitioners are fully aware of the importance of AMS, in order to avoid a future with no appropriate antimicrobials and therefore an inability to manage wound infections.