From the Guidelines
For skin culture, a sterile cotton or polyester swab is recommended, but the most recent and highest quality evidence suggests that tissue specimens are preferred over swabs for determining the causative microorganisms and their antibiotic sensitivity 1. When considering the type of swab for skin culture, it's essential to prioritize methods that enhance bacterial recovery while minimizing contamination.
- Sterile cotton or polyester swabs are commonly used for skin cultures.
- These swabs should be moistened with sterile saline or transport medium before sampling to enhance bacterial recovery, especially from dry skin lesions.
- The swab should be firmly rolled over the affected area, focusing on the advancing edge of the infection or wound rather than the center, as this is where active bacterial growth typically occurs.
- After collection, the swab should be placed immediately in an appropriate transport medium to preserve the viability of microorganisms. However, the guidance from 1 emphasizes the importance of obtaining cultures from tissue specimens rather than swabs when possible, as this method provides more accurate information on the causative microorganisms and their antibiotic sensitivity. The use of swabs is generally recommended when tissue specimens are not feasible, and the method of swab collection and handling is crucial for optimal results.
- Collecting the sample before starting antimicrobial therapy is also recommended, as antibiotics can interfere with bacterial growth in culture 1. Given the available evidence, the choice of swab type should be secondary to the decision of whether a swab or tissue specimen is the most appropriate sample for culture, with tissue specimens being the preferred method when possible.
From the Research
Types of Swabs for Skin Culture
- Cotton swab: A study from 2 found that the cotton swab technique is an efficient and reliable method for obtaining material for culture of dermatophyte infections.
- Dry swab: Research from 3 and 4 compared the use of dry swabs with other methods, such as sterile gauze and TranswabTM, for skin sampling and found that dry swabs had a lower positive culture rate.
- Wet swab: A study from 4 used a wet swab (0.15 M NaCl and 0.1% Tween 20) for skin sampling and found that the collection method (wet vs. dry) affected measures of bacterial diversity.
- Sterile gauze: Research from 3 found that sterile gauze rubbing skin sampling had a higher positive culture rate compared to TranswabTM and dry swab.
- TranswabTM: A study from 3 compared the use of TranswabTM with sterile gauze and dry swab for skin sampling and found that TranswabTM had a lower positive culture rate.
Specific Swab Types for Certain Conditions
- For dermatophyte infections: Cotton swab 2
- For Malassezia yeast: Sterile gauze 3
- For skin microbiome research: Dry swab or wet swab 4
- For identifying bacteria in sinus tracts or tunneled wounds: Cotton swab with bacterial fluorescence imaging 5
- For MRSA detection in skin and soft tissue infections: MRSA PCR wound swab 6