A wound swab arrives into the microbiology laboratory..

…Because there are no clinical details we don’t know whether a Gram stain might be worthwhile.

Because there are no clinical details, we don’t know whether to add anaerobic culture or set up a yeast agar for this  swab.

Because there are no clinical details, we don’t know whether this Pseudomonas aeruginosa isolate on the plate is potentially significant…

Microbiology laboratories all over the world (including our own) receive hundreds of wound swabs every day. Often there are no clinical details or only a very cursory acknowledgement to this requirement, such as “?infection”, or “discharging wound”.

You know the story well…

So often we are left to process and report the wound swab with no idea of what is actually wrong with the patient, and what exactly we should be doing with the swab.

In my opinion clinical details involve two main elements, which overlap to a certain extent:

• Contextualisation- What type of infection are we dealing with here? Taking the example of skin infections; Is it an impetiginous lesion, is it a boil, is it an area of cellulitis, is it a post-surgical wound, is it a burn, etc, etc? By providing clinical context we can start to work out what we are looking for and ascertain the importance of potential pathogens on the agar plates. Is there anything we should know about the patient? Are they immunocompromised? Do they have antibiotic allergies? Are they failing treatment? Is there anything unusual about the clinical presentation? Was it caused by a bite? Was there overseas travel?
• Justification- Taking the example of skin infections again, most patients with impetigo & boils, along with many other types of uncomplicated skin infections, do not need a wound swab sent to the lab. For most skin infections, swabbing should be the exception, not the rule. So what was it about this particular patient that prompted the clinician to send a wound swab? Was it because the patient failed first line treatment? Was it because they had an associated fever? Was it because the infection was getting rapidly worse?

Here are a few examples of hypothetical clinical details that both contextualise and justify the swab.

• “Impetiginous lesions on face getting worse despite topical anti-septic treatment. Past history of MRSA colonisation.”
• “Area of spreading cellulitis L lower leg. Patient diabetic.”
• “Carbuncle L buttock, patient has an anaphylactic allergy to penicillin.”
• “Cat scratch to R hand. patient now has fever and increasing erythema. Commenced on amoxycillin-clavulanate.”

It’s not rocket science, nor does it have to be a story.

If the clinician is required to contextualise and justify the laboratory request, then the advantages are two-fold. Not only can the scientist paint a picture in their head of what is going on with the patient, and process accordingly, but also the clinician may start to think twice about why they are sending a particular sample to the laboratory in the first place…

Michael