Principles of infection control
Obtaining swabs
Learning outcomes
Having read this chapter, the reader should be able to:
Swabs may be obtained when infection is suspected so that the correct antibiotics are administered which are specific to the infecting microorganism or for screening purposes to help inform care, e.g. methicillin-resistant Staphylococcus aureus (MRSA) screening, history of vaginal group B streptococcus (GBS). Increasingly pre-admission screening, often with nasal and groin swabs, is being undertaken prior to elective surgery, e.g. caesarean section, to detect MRSA and reduce the incidence of surgical site infections. While screening for MRSA seems to be acceptable to the ‘patients’, it is important they are aware of the implications of a positive result and that screening is undertaken with sufficient time for treatment to avoid delaying surgery (Currie et al 2013). Early recognition and treating of infection is essential to avoid genital tract infection which was the second highest cause of direct maternal deaths in 2010–2012 (Knight et al 2014). Group A streptococcus (GAS) is a common microorganism involved in maternal infection particularly in early pregnancy and the postnatal period (Churchill et al 2014). It is a common cause of sore throats, particularly in children, and is often a community-acquired infection. Strict adherence to hand hygiene, particularly before and after changing sanitary pads may help to reduce the incidence of infection (Harper et al 2011). When obtaining a swab because of suspected uterine or perineal infection, it is best to do so before antibiotics are used. This chapter focuses on obtaining swabs from the more common sites of the eye, ear, nose, throat, groin, umbilicus, vagina, wound and placenta.
Good practice
Good practice for the taking of all swabs should include:
Obtaining the swab
Sterile swabs are usually made of cotton or rayon attached to a long stick and when obtained they are placed whole into a transport medium. It is vital that the swab stick used is sterile and in date, as this can affect the results. The lid should be firmly tightened and correctly labelled, including the woman’s name, hospital number, date of birth, specimen taken, and time and date, all of which should correspond with the pathology form (this should also indicate if the woman is taking antibiotics and any signs or symptoms). The swab is then placed in a transport bag that is sealed to prevent spillage and contamination with the pathology form and taken to the laboratory as soon as possible, as microorganisms can multiply when kept at room temperature. If delay is anticipated, refrigeration may be necessary (although some swabs can be kept at room temperature); it is therefore important the midwife is aware of how to store swabs and specimens when they cannot be transported quickly. In high-risk situations, the swab may need to be double-wrapped and labelled accordingly.
The laboratory test requested is usually ‘microscopy, culture and sensitivity’ (MC&S) which involves a microscopic examination for a quick initial report of the microorganism(s) present, culture of the microorganism(s) to identify which microorganisms are present, a microbial count to determine if they are the result of colonization or infection and an analysis of sensitivity to antibiotics that can be administered to prevent further growth and replication.
When taking the swab, it is important that the microorganisms coat the swab all over to increase the chances of identifying the infecting microorganism and this is best achieved by rotating the swab over the site of swabbing. An Aseptic Non Touch Technique (Chapter 10) should be used to avoid cross-contamination and only the affected area should be swabbed (Dimech et al 2011). In some situations, a sample of pus, exudate, moisture, etc. from the woman or baby (e.g. from the umbilical stump) may need to be collected. While they can be collected via a swab stick, it may be more appropriate to use a sterile syringe to collect pus/exudate. Standard precautions, including hand hygiene, should be followed when obtaining a swab (Chapters 8, 9). Where swabs are required from more than one site (e.g. both eyes, ears), a separate swab should be used for each site to reduce the risk of cross-infection from an infected to a non-infected area. However, usually only one swab is required from the area that appears most affected.
There are a variety of transport mediums as different microorganisms can thrive or die in certain mediums, thus it is important that the correct swab and transport medium are used for the suspected microorganism, for example, Trichomonas vaginalis, Chlamydia spp. and Bordetella pertussis require charcoal-based swabs and medium. If the midwife is unsure of which swab and transport medium to use, she should ask a doctor or microbiologist who should be able to advise.
The midwife should record in the notes which swabs have been taken and the time and date. This will ensure that all staff are aware the swabs have been obtained and will serve as a reminder to check the results as soon as they are ready. The woman should also be aware of why the swab/s are undertaken and how soon she can expect to have the result.
Eye
When obtaining an eye swab from a woman, she should be sat up, with her head supported and the woman asked to look upwards to prevent corneal damage (Dimech et al 2011). If the swab is from a baby, he should be supported with his head held steady. The lower eyelid should be pulled down gently. The swab is held parallel to the cornea and rubbed very gently against the conjunctiva in the lower eyelid moving from the inner canthus to the outer canthus. If Chlamydia is the suspected microorganism, apply slightly more pressure when swabbing (Dimech et al 2011). It is important to avoid touching the eyelid borders or eyelashes with the swab. Usually just one swab is sufficient. If Gonococcus is the suspected organism, the swab should not be refrigerated as there will be no recovery of the Gonococcus organism and a false negative will be reported.
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