(CS-149) What is Wound Slough? A pilot study to define the proteomic and microbial composition of wound slough and its implications for wound healing.

J.Z. Alex Cheong, B.S – University of Wisconsin-Madison, School of Medicine and Public Health, USA; Gregory Schultz, Ph.D. – International Wound Infection Institute; Obstetrics and Gynecology, University of Florida; Matthew Malone, Ph.D. – Infectious Diseases and Microbiology, Western Sydney University,; Thomas Bjarnsholt, MD, Ph.D. – Department of Clinical Microbiology, Copenhagen University Hospital; Michael Radzietza, Ph.D. – Infectious Diseases and Microbiology, Western Sydney University; Blaine Fritz, Ph.D. Student – Department of Clinical Microbiology, Copenhagen University Hospital; Karen Ousey, Ph.D. – Institute of Skin Integrity and Infection Prevention, University of Huddersfield; Terry Swanson, MHS – School of Nursing, Queensland University of Technology; Angela Gibson, MD – University of Wisconsin-Madison, School of Medicine and Public Health; Lindsay Kalan, Ph.D. – University of Wisconsin-Madison, School of Medicine and Public Health

Introduction: Slough is a well-known feature of non-healing wounds. However, the tissue and microbial composition of wound slough is not well defined. Whether the composition of this slough has implications for a wound’s ability to heal is also unknown. The aim is to determine the proteomic and microbiologic components of slough as well as interrogate the associations between wound slough components and wound healing.

Methods: Ten subjects with slow-to-heal wounds and visible slough were enrolled. Swabs of the wound surface were collected via the Levine technique and sent for high-throughput bacterial 16S ribosomal gene sequencing. Wound slough was removed with sharp debridement and sent for scanning electron microscopy (SEM), fluorescence in situ hybridization (FISH) staining, and proteomics. Wound etiology and patient co-morbidities were extracted from the medical record. Whether the wound healed, was stable, or got worse 3-months following sample collection was also recorded.

Results: The age of wounds ranged from 0.1-15 years. Etiologies included venous stasis ulcers, trauma, post-surgical site infections, and pressure ulcers. Wound locations included over the sacrum, on the shin, lower leg, or ankle. SEM and FISH imaging reveled wound slough to be heterogenous, often amorphous in structure. 16S-profiling found wound slough microbial communities were associated with the wound’s etiology and its location on the body (both PerMANOVA p-values < 0.01). Wound Slough was largely composed of proteins related to the skin barrier, blood clot formation, and immune processes. Three of the subject’s wounds had healed 3-months following sample collection. Wounds that healed were enriched for proteins involved in skin barrier development, wound healing, and immune responses to bacteria (absolute log Fold Change (LogFC) > 2, p-value < 0.01). Conversely, wounds that got worse were enriched for proteins associated with chronic inflammatory responses, and the compliment cascade (absolute LogFC > 2, p-value < 0.01).

Discussion: Wound slough contains complex microbial communities as well as a milieu of skin and immune associated proteins. Slough enriched for chronic inflammatory proteins were associated with wound progression 3-months later. The presence of these proteins in slough could serve as markers for wounds at higher risk for continued impaired wound healing.