The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [424]
Obtaining swabs is a key component of an effective MRSA prevention programme and certain patient groups are deemed to be at higher risk of contracting serious MRSA infections: critical care, burns, transplantation, cardiothoracic surgery, orthopaedic surgery, trauma, vascular surgery and renal patients (Coia et al. 2006).
The normal habitat of Staphylococcus aureus, including MRSA, is human skin, particularly the anterior nares (nose), axilla (armpit) and perineum (groin) (DH 2006). The most commonly sampled site for MRSA screening is the nose, which can detect up to 80% of MRSA-positive patients (DH 2006). If samples from other sites, such as the groin, are included in the screening regime, detection of MRSA-positive patients increases to 100% (DH 2006). Other samples can be taken from the following sites: skin lesions and wounds, invasive line sites and other skin breaks, tracheostomies, catheter specimens of urine (CSU) and sputum from patients with a productive cough (Coia et al. 2006). The microbiological request form should clearly indicate that the samples are for MRSA screening to ensure that correct laboratory techniques are used and to avoid potential waste of resources.
Evidence-based approaches
Rationale
Indications
Taking a swab is indicated:
if there are clinical signs of infection which may manifest as symptoms such as pain, redness, inflammation, heat, pus, odour and so on
if a patient shows signs of systemic infection or has a pyrexia of unknown origin (PUO)
as part of a screening programme.
Contraindications
As routine use (unless part of a screening regimen).
On chronic wounds which will be colonized with skin flora.
Principles of care
Although swabs are relatively simple to use, absorbency of infected material is variable and adequate material collection that is representative of pathogenic changes, for example to wounds, is often dependent upon correct sampling technique (Gould and Brooker 2008). Swab specimens should be collected using an aseptic technique using sterile swabs, with the principal aim of gathering as much material as possible from the site of infection/inflammation. Care should be taken to avoid contamination with anything other than sample material such as surrounding tissue, which will be contaminated with other pathogens such as skin flora (Weston 2008).
If an infected area is producing copious amounts of pus or exudate, a specimen should be aspirated using a sterile syringe because swabs tend to absorb excess overlying exudate, resulting in an inadequate specimen (Gilchrist 2000). If the area to be swabbed is relatively dry, for example nasal or skin swabs, the tip of the swab can be moistened with sterile 0.9% sodium chloride which makes it more absorbent and increases the survival of pathogens (Weston 2008).
Obtaining a swab should be considered in conjunction with a comprehensive nursing assessment. This could include observation of localized infection such as inflammation or discharge from a wound during a dressing change.
Practitioners should know what type of pathogenic micro-organisms they are testing for, for example whether a bacterial or viral infection is suspected, as this will determine which swab is the most appropriate. Advice should be sought from the microbiology laboratory prior to taking a swab to ensure appropriate and resource-effective sampling or specimen collection. For example, whilst viruses cause the majority of throat infections, group A streptococcus is the main bacterial cause of sore throats and therefore if suspected, a swab with bacterial transport medium would need to be used rather than one containing viral transport medium.
Legal and professional issues
Competencies
Obtaining specimens for microbiological analysis is a key component in the patient