Comparing flocked swab to nylon fabric curettage brush for the detection of infections in hard-to-heal wounds
Pejman Rahimian, Mervin Low, Neal LonkyObjective:
Accurately identifying microbial burden, especially biofilm-encased organisms, is crucial for managing hard-to-heal (chronic) wound infections and guiding antimicrobial use. Swab sampling, while common, may underestimate the presence of pathogens beneath the wound surface. Tangential biopsy with a nylon fabric curettage brush offers a promising alternative, capturing both surface and subsurface organisms for a comprehensive tissue overview.
Method:
A retrospective, blinded, paired-sample case series was conducted with patients with hard-to-heal wounds. For each patient, two samples were collected: one using a flocked swab (flocked swab) (ESwab, Copan Diagnostics, US), the other using a nylon fabric curettage biopsy brush (biopsy brush) (Kylon fabric, SoftBiopsy device, Histologics, LLC, US). All samples were processed under identical conditions at a reference laboratory. DNA was extracted and amplified using validated polymerase chain reaction assays, and the microbial load was measured as colony forming units per millilitre (CFU/ml). Device performance was assessed based on: concordance; sensitivity; nucleic acid yield; and its impact on infection classification.
Results:
This was a case series of eight patients. Pathogen detection concordance was 65%. The biopsy brush had slightly higher sensitivity (84%) than the flocked swab (81%) and produced 30% more nucleic acid, with 71% showing lower cycle thresholds than the flocked swab. In 41% of microbial and resistance gene targets, the biopsy brush changed interpretation of microbial burden from a level consistent with colonisation to one more consistent with infection, according to the study's predefined CFU/ml interpretive criteria. In 50% of patients, results using the biopsy brush changed infection classification.
Conclusion:
Both sampling methods detected wound pathogens; however, the nylon curettage biopsy brush demonstrated superior nucleic acid recovery and diagnostic yield compared to the flocked swab. By more accurately measuring microbial burden, this minimally invasive biopsy technique may enhance the detection of infections and support targeted therapy in hard-to-heal wound care.