Infections in wounds can not only prolong a patient's recovery but do them additional injury. When a wound shows signs of being infected (it may be slow to heal, issue a purulent discharge or give off a noxious odour) the wound is sometimes "swabbed" to test it for infection. Wound swabbing, a medical practice particularly popular in Britain, is a means of measuring the amount of bacteria within a wound by sampling exudate from the surface of the wound. The exudate is collected on a swab and then cultured in a petri dish. While there are a number of methods of swabbing, the following is generally considered to be the most effective.
- Skill level:
- Moderately Easy
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Things you need
- Cotton swab
- Transport medium
- Refrigerator (optional)
Clean the wound with a gentle stream of saline, making sure to clear out all obstructive debris. This will remove other nonbacterial contaminants, such as skin cells, and allow access to the deepest part of the wound. Do not apply antiseptic solutions or local anesthetics, as these will kill topical bacteria and possibly cause a false negative reading.
Moisten the swab prior to touching the would. According to a study on wound-swabbing technique that appeared in the "Nurses Times" journal, this makes the swab more absorbent and increases the rate of survival for bacteria prior to the microbiological culture.
Apply the swab to an area of viable tissue, not scab or slough. This is because organisms that cause infection are most likely to be found in viable tissue. Do not draw from pooled exudate or from wound dressings, as these likely contain contaminants.
When sampling, rotate the swab and move it in a zigzag motion across the wound. If possible, the whole wound should be swabbed, particularly those parts of the wound showing the most severe signs of infection, such as those expelling fresh exudate.
Transport the swab in the transport medium to the lab for culturing as quickly as possible. If the lab will not be able to culture the swab within 24 hours, store it in a refrigerator at 3.89 degrees C.
Tips and warnings
- Make sure to swab the wound before the patient has begun antibiotic therapy, so as not to foul the results.
- Many researchers believe that because wound swabs only sample surface organisms, not organisms within the tissues, they are unreliable means of measuring infection. Part of the reason is that the techniques used to swab vary greatly. Variables include how the wound is prepared, what part of the wound is sample, how long the swab remains on the wound, and the type of swab used. These inconsistencies make comparisons with other techniques of measuring infection very difficult.
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