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Current Practice in the management of wound infection

Wound infection can have a devastating effect on the wellbeing of the patient, their quality of life, the cost of treatment, and can be potentially life-threatening. The delicate balance and mutually beneficial relationship between normally non-pathogenic, resident bacteria and exogenous bacteria (from the hands or environment) remains intact until the protective skin barrier has been breached. The potential for infection increases as the bacteria contaminate the exposed tissues and penetrate deeper colonising and causing a local reaction, particularly in people with compromised immune systems. 

The mystery is why many, but not all, contaminated or colonised wounds succumb to wound infection while others do not. Nurses in all care settings must have a basic understanding of the mechanism of wound healing and microbiology to enable them to recognise those people who are at risk of infection and the signs and symptoms of wound infection. The aim is to prevent infection, facilitate healing and avoid its potentially life-threatening effects.

In addition to the costs to the NHS, estimated to be £2.3-£3.1 billion (2005-6) for chronic wounds alone,1, surgical site infections (SSI) account for 20% of hospital acquired infections (HAI) with over one third of post-operative deaths related to SSI.2 These costs place an additional burden on NHS and individuals' resources and unnecessary risk to patients. 

The Health and Social Care Act 2008 code of practice on the prevention and control of infections and related guidance imposes a legal duty on organisations to consistently implement effective infection prevention and control measures. The development of National Institute of Health and Care Excellence (NICE) Quality Standards3 can contribute to achieving the NHS Outcomes Framework 2014-15, particularly in relation to Domain 1, which is preventing people from dying prematurely.4 

 

Risk factors for wound infection

Wound infection occurs when the fine balance between the patient's immune response and type of wound versus the type, quantity and virulence of the micro-organisms in the wound is disrupted.5 The vulnerability of the patient will be influenced by a number of systemic problems. These include a defective circulatory system, anaemia, respiratory disorders, poor nutritional status, particularly protein and vitamins,6 metabolic disorders such as diabetes mellitus,7 concurrent infections, medications that adversely affect the immune system such as steroids or chemotherapy,7 obesity,8 stress,9 and ageing, as examples. 

Accurate medical and nursing assessment is essential to identifying and managing, where possible, these risk factors and implementing contingency plans for those that cannot be modified. Standard infection control precautions should be followed to reduce the risk such as effective hand decontamination, use of personal protective equipment, correct disposal of waste, etc. 

 

Identifying wound infection

Wounds may heal by primary intention using various closure techniques or secondary intention, when the wound is left open because of the presence of infection, excessive trauma or skin loss and the wound heals through the formation of granulation tissue and contraction. Tertiary intention or delayed primary intention healing occurs when the initial infection risk is very high usually due to the mechanism of injury and are intentionally left open to allow resolution of oedema and/or infection and closed at a later date if appropriate. In all cases the wound may be partial or full thickness penetrating through the epidermis to bone, muscle or tendon in the latter. Open wounds will always be at risk of infection.

Wound infection is defined as the presence of multiplying organisms which overwhelm the body's immune system resulting in spreading cellulitis (inflammation of the tissues).10 This implies systemic disease that is likely to impede healing and potentially lead to bloodstream infection or septicaemia. 

The classic signs and symptoms of wound infection of heat, redness, pain, swelling and loss of function have been explored and extended to include delayed healing, increase in size or change of shape, bridging and general breakdown, tissue fragility and associated bleeding, cellulitis, increased exudate or collection of pus or fluid, pain in or around the wound or offensive odour. In addition, the patient may feel hot and generally unwell. The number of micro-organisms and their degree of virulence will influence whether a wound becomes infected but the bacterial burden or bioburden particularly in immunocompromised patients, the findings of foreign material, necrotic tissue or clotted blood provide ideal foci for microbial multiplication in the wound.11 

Wound colonisation is defined as the presence of multiplying micro-organisms on the wound surface but with no host immune response;12 there may be no signs and symptoms. However, colonisation may develop into critical colonisation as the number and/or virulence of the micro-organisms increase and the host can no longer control the bacteria, and result in infection.13 Relatively recently, the concept of biofilms has attracted interest; these comprise complex, continuously changing microbial communities containing bacteria and fungi which synthesise and secrete a protective matrix that attaches the biofilm firmly to a living or non-living surface.14 Following attachment, the organisms are protected from external threats such as antimicrobial agents and the immune system by being encased in a gelatinous, thick, slimy barrier of sugars and proteins. Chronic wounds have polymicrobial infections, sometimes with dozens of microorganisms (bacteria and yeast) all existing as a co-operative community. The presence of biofilm may be suspected in chronic inflammation and/or non-healing wounds, however, it is difficult to identify but is needed to direct treatment.15

 

Sampling for infection

There exists controversy regarding the best sampling technique for identifying wound infection. The options include wound swabbing, needle aspiration and wound biopsy. One drawback of wound swabbing is that it may only identify surface colonising pathogens not the deep-seated infecting pathogens. The most accurate information about the type and quantity of pathogenic bacteria is provided by wound biopsy but it is an invasive procedure, not taught as a nursing skill and will be reserved for non-healing wounds despite treatment for infection.16 

It has been suggested that routine swabbing, such as at weekly intervals or at the time of frequent dressing changes, is neither helpful nor cost-effective.17 The diagnosis of infection in chronic wounds should be made on the clinical signs and symptoms and supported by the results of laboratory tests18 rather than the other way around. The usual practice of taking wound swab for culture augments the process of clinical decision-making and they should not be taken without good clinical rationale.  

Wound infection risk in surgical wounds is increased by contamination peri-operatively, long procedure, large/deep wounds, trauma with delayed treatment, the presence of a foreign body and location in a site of possible high contamination, eg. perineum. The duration and presence of necrotic tissue in a chronic wound will attract bacteria and increase the risk of infection. 

A comprehensive summary of the signs and symptoms of infection in acute and chronic wounds can be found in the World Union 

of Wound Healing Societies (WUWHS) publication Wound Infection.16

 

Assessment

The concept of wound bed preparation (WBP) has been widely adopted as a method for ensuring that everything is done to ensure that optimum conditions for healing to proceed effectively are put in place. WBP19 and TIME (tissue [non-viable or deficient], infection/inflammation, moisture [imbalance] and edge [non-advancing or undermined])20 are systematic frameworks that can help to formalise the assessment and may positively contribute to ideal, individualised patient and wound management. The aim of wound bed preparation is to remove the barriers to healing and initiate the repair process with the effective management of bacterial bioburden as an essential element of wound management. 

 

Management of wound infection

The aim of management, following a holistic patient assessment and infection has been diagnosed and antibiotic sensitivities identified, is to optimise the patient's general health status, reduce the bacterial burden, facilitate healing and reduce the risk of cross contamination. Broad-spectrum antibiotics may be used in non-healing wounds or those at high risk of infection to provide a high local concentration and avoid systemic allergic reactions.21 However, their effect may be reduced by the presence of ischaemic and necrotic tissue22 and the growing concerns about antibiotic resistance must be considered. 

Despite past concerns about the use of topical antiseptics, the discriminate, short-term use of, for example cadexomer iodine and the newer silver formulations, may be beneficial23 but more research is needed. The three main generic groups of wound dressing products that have the potential to reduce the bacterial burden in infected wounds are those containing silver, honey and iodine. Larval therapy has grown in popularity due to its perceived beneficial effects of reducing the bacterial burden, odour and exudate. Box 1 lists some of the antiseptics that may be considered for the treatment of infected wounds. In recent years the increased use of topical antimicrobial dressing products to control colonisation and infection and yet there is concern that some preparations may inhibit wound healing and may have systemic consequences. More research is required. The practical aspects of odour and excess exudate will often be patients' primary concerns so efforts must be made to understand and address these problems from the patient's perspective and address.

 

Conclusion 

The NICE Quality Standard states that appropriate wound and dressing care promotes healing and reduces the risk of wound infection and that providing information and advice to patients and carers will reduce contamination. The timely implementation of suitable and effective treatments based on the early identification of an increased bioburden has the potential to significantly improve patient outcomes, reduce costs and limit incriminate use of antibiotics.