Wound cultures

Identifying high bacteria levels and/or infection in wounds is based on a holistic assessment with clinical signs and symptoms playing key roles in diagnosis. However, there may be times that the initial assessment may indicate the need for microbiological analysis to confirm the diagnosis and guide management. As it is inappropriate to culture all wounds, the following guidelines can help determine when a wound culture may be needed:^1,2

Sampling techniques include wound swabbing, needle aspiration and wound biopsy. A wound biopsy (considered the gold standard) provides the most accurate information about type and quantity of pathogenic bacteria, but is invasive, skill-intensive and unavailable in many settings.³ The biopsy is used most often for wounds that are failing to heal despite treatment for infection.¹ The needle aspiration method which involves insertion of a 22-gauge needle into the tissue surrounding the wound, also has the same challenges as the biopsy as it is also invasive, skill-intensive, frequently unavailable and in addition it can be painful.³ The third method, the swab culture, is by far the most frequently used and easiest technique to use. The most common swab culture techniques are the Levine and Z-stroke techniques. Comparing both with the biopsy as criterion standard, the diagnostic accuracy to diagnose a chronic wound infection by the Levine technique has proven better results in comparison with the Z-stroke.⁴ The Z-stroke technique is performed by rotating the swab from margin to margin in a 10-point zigzag fashion across the wound.³ The Levine technique provides findings most comparable to the wound biopsy as this technique samples microorganisms from within the wound tissue, not just from the wound surface.³ To perform the Levine swab culture follow these steps:²