The value of slough in wounds for the diagnosis of microbiology cultivation.

Slough is not currently a recommended microbiology culture specimen. The aim of our work is to analyse the concordance of results between slough and swab samples for cultures. A single-centre, retrospective, cross-sectional study involving patients (n = 131) with hard to heal wounds was conducted from October 2022 to October 2023. Pairs of slough and swab samples were collected for microbiological analysis and subdivided depending on whether a relatively clean wound bed was obtained. Swab samples were collected using the Levine and deep pus methods, Cohen's κ coefficients calculated to evaluate concordance, and microbiological agreement analysed. Gram-stain results did not differ significantly between slough and swab samples (𝜒² = 329.287, p = 0.688; concordance, κ = 0.879, p < 0.001); microbiological agreement was 90.1%. Samples from 87 patients with relatively clean wound beds generated excellent concordance between slough and Levine technique (κ = 0.867, p < 0.001; microbiological agreement, 89.7%). In 44 patients with slough and deep pus swab where a relatively clean wound bed could not be obtained, Gram-stain also demonstrated excellent concordance (κ = 0.898, p < 0.001; microbiology agreement, 90.9%). Our data provide evidence that slough is a reliable wound specimen from hard to heal wounds for microbiology culture.