Visiting Professor of Wound Healing Research University of Bradford
Consultant Vascular Surgeon
Teaching Hospitals NHS Foundation Trust
Immediate Past President
European Wound Management Association
Medical Education Partnership Ltd
Editorial Project Manager
Medical Education Partnership Ltd
Concerns about hospital-acquired infection and bacterial resistance have become a major political issue in many European countries. While the lay media may be criticised for overhyping the problems, healthcare professionals clearly have a renewed responsibility to promptly and accurately recognise episodes of infection and to treat them appropriately. The most recent position documents from the European Wound Management Association give healthcare professionals practical and measured advice on these pertinent issues. Last year’s document explores and develops criteria for identifying wound infection, while this year’s document builds on the concepts to provide clear, evidence-based recommendations for tackling complex treatment decisions.(1,2)
Understanding wound infection
To treat wounds successfully it is important to appreciate the intricate mechanisms involved in infection. Infection is the end result of a complex interaction between host, organism, wound environment and therapeutic interventions.(1) This is complicated by bacterial cooperation and virulence. It is the balance and interplay between these factors that determine whether the host–pathogen interaction leads to disease. The presence of microbes in wounds can result in three clearly defined outcomes: contamination, colonisation and infection. A further situation – critical colonisation – was proposed after studies suggested a continuum of states between colonisation and infection.(3) Definitions of these states reflect the elaborate interactions and must be definitively characterised.
Clinical identification of wound infection
Because our knowledge of host–pathogen interactions is limited, holistic assessment of patients is more reliable for diagnosing wound infection than microbial assessment alone. However, clinical identification of wound infection is itself a challenge. Criteria developed in 1994 emphasised the value of additional “subtle” signs, which had previously been largely unrecognised.(4) Subsequently, an international, multidisciplinary group of 54 wound care experts generated criteria for identifying signs of wound infection in six different wound types.(1) To do this they used a method known as the Delphi process – a practical method for developing consensus based on group response, where participants are provided with a set of issues on which to rank their views.
A key consideration was the fact that, despite some common criteria, each wound type may present with different clinical signs of infection that could provide vital clues for early identification. Some new and interesting criteria were generated. For example, ecthyma gangrenosum is usually regarded as a rare complication of burns; but the panel ranked this highly in both partial- and full-thickness wounds. The full criteria are detailed in the position document and at www.ewma.org.(1,5) The criteria must be evaluated and validated, but they provide a valuable stimulus for further debate.
Pressure ulcer infection
Early diagnosis and treatment of patients with grade 3 or 4 pressure ulcers is difficult because the signs of chronic inflammation are similar to those of overt infection. The Delphi criteria specific to pressure ulcer infection are listed in Box 1. The classic signs are included, but some have usefully been described in more detail (eg, “spreading erythema” and a “change in nature of pain”). Importantly, the presence of pus was not included; determining this is difficult in these wounds, and some dressings can give exudate a pus-like appearance. New criteria, such as “viable tissues become sloughy” and “crepitus”, were identified.
Surgical site infection
A different set of challenges face clinicians diagnosing infection in acute surgical wounds. Even with experience and knowledge, early identification is difficult because the wound may not be open to observation. Several wound scoring systems exist, but these are designed predominantly for auditing, classification and surveillance.
The Delphi criteria specific to wounds healing by primary intention go some way towards rectifying this, although they have limitations and it is clear that accurate diagnosis depends on looking at several criteria in combination.
Managing wound infection
A wound does not need to be sterile to progress towards healing, and the 2006 position document on managing wound infection pays particular attention to appropriate use of topical antimicrobials (excluding topical antibiotics).(2) While robust evidence is sparse, the authors have critically appraised the literature and have formulated recommendations to help clinicians make practical decisions.
An integrated approach
Antibiotic use should be limited to specific clinical situations (eg, overt infections) and directed towards susceptible organisms. Using the early signs discussed above, clinical stages of infection can be defined and used to determine a treatment strategy.(1) The algorithm (Figure 1) gives a protocol for managing potential and overt infection. The principles underpinning this guidance are to:
- Provide an optimal environment to promote rapid healing.
- Minimise the use of antimicrobials that may adversely affect human cells.
- Use antimicrobials appropriately to reduce the selection of resistant strains.
- Restrict the use of systemic agents to occasions when they are specifically indicated.
- Avoid topical sensitisation or allergic reactions.
Wound status must be regularly reviewed, and management strategies changed when progress towards healing is not achieved.
Silver has been used in wound care for centuries and has a key role today. Nonetheless, we still do not fully understand its mechanisms of action and it is therefore timely to look at its molecular activity, rationale for use and limitations as an antimicrobial.(2) Silver is a broad-spectrum antimicrobial with a low toxicity in wound applications. Its molecular activity is thought to be due to interference with cell respiration and interruption of DNA transcription.(6,7) It is active in its ionic form and this is not greatly affected by dilution because of its low concentration exponent. Advances in impregnation techniques and polymer technologies have fuelled the latest interest in silver-based dressings, and these appear to have a better antimicrobial efficacy than do silver alone.(8,9) However, there is evidence of bacterial resistance to silver and its use needs to be supported by further evaluation.
Infected pressure ulcers
Newer formulation topical antimicrobials (particularly silver and iodine products) are increasingly being recommended as part of the management of grade 3 and 4 pressure ulcers. Considerations when choosing a dressing include: wound condition, exudate level and adaptability of the dressing to suit the wound.
Surgical site infection
Although antiseptics have a major role in preventing infection during surgery, good quality trials are needed before antimicrobial dressings can be recommended for routine use. The best evidence is for their role in skin preparation before surgery. They are unlikely to benefit closed surgical wounds because of insufficient penetration. However, data suggest they can be used as a “rescue remedy” for infected wounds that are failing to heal.(10) Indications include:
- Wounds with a necrotic or poor blood supply.
- Wounds continually recontaminated or infected (eg, faecal fistulae).
- Patients with specific antibiotic allergy or antibiotic-resistant infection.
- Wounds benefiting from delayed primary closure principle.
A systematic review of topical agents for wounds healing by secondary prevention found no evidence to support their use.(11)
Not all wounds will become infected and level of suspicion will vary according to host status, susceptibility to infection and the consequences of infection. Using topical antimicrobials simply to lower microbial load in a healing wound is not justified. However, by using the Delphi panel’s criteria for identifying wound infection as a starting point, clearer guidance can be provided on using topical antimicrobials appropriately.
- European Wound Management Association. Position document: identifying criteria for wound infection. London: MEP Ltd; 2005.
- European Wound Management Association. Position document: management of wound infection. London: MEP Ltd; 2006.
- Kingsley A. A proactive approach to wound infection. Nurs Stand 2001;15:50-8.
- Cutting KF, Harding KG. Criteria for identifying wound infection. J Wound Care 1994;3:198- 201.
- Loebl EC, Marvin JA, Curreri PW, Baxter CR. Survival with ecthyma gangrenosum, a previously fatal complication of burns. J Trauma 1974;14:37077.
- McDonnell G. Russell AD. Antiseptics and disinfectants: activity, action, and resistance. Clin Microbiol Rev 1999;12:147-79.
- Richards RM. Antimicrobial action of silver nitrate. Microbios 1981;31:83-91.
- Wright JB, Lam K, Hansen D, et al. Efficacy of topical silver against burn wound pathogens. Am J Infect Control 1999;27:344-50.
- Yin HQ, Langford R, Burrell RE. Comparative evaluation of the antimicrobial activity of ACTICOAT antimicrobial barrier dressing. J Burn Care Rehabil 1999;20:195-200.
- Grubbs BC, Statz CL, Johnson EM, et al. Salvage therapy of open, infected surgical wounds: a retrospective review using Techni-Care. Surg Infect 2000;1:109-14.
- Vermeulen H, Ubbink D, Goossens A, et al. Dressings and topical agents for surgical wounds healing by secondary intention. Cochrane Database Syst Rev 2004;(2): CD003554.