Skin-Dwelling Bacteria Survive Preoperative Skin Preparation in Reconstruction Surgery

<b>Background/Objectives:</b> Accurately determining the bacterial bioburden that survives preoperative skin preparation (PSP) is critical in understanding PSP efficacy and its limitations. Clinical PSP approval relies on a bacterial sampling method described in the American Society for Testing and Materials (ASTM) standard E1173-15. Though common, this technique may overlook deep-dwelling skin bacteria. The objective of this study was to test the hypothesis that deep-dwelling skin flora would survive PSP, and more growth would be detected using a destructive sampling method compared with ASTM E1173-15. <b>Methods:</b> Twelve female participants with a scheduled deep inferior epigastric perforator (DIEP) artery flap procedure at the Huntsman Cancer Institute in Salt Lake City, UT, were enrolled between January and August 2024. PSP was performed using three 26 mL ChloraPrep applicators (2% CHG), and excess tissue was collected. Bacteria in the skin were quantified using a destructive sampling method and ASTM E1173-15, and bioburden outcomes were compared. Two participants were excluded from the quantitative analysis. <b>Results</b>: Bacteria survived PSP in every participant. A greater diversity and more bacteria were quantified with destructive sampling than ASTM E1173-15 (<i>p</i> < 0.01). Generally, anaerobic bioburden values were higher than aerobic bioburden values. Higher bioburden correlated with processing more skin from a participant. Genotypic identification of select isolates identified <i>Staphylococcus epidermidis</i> and <i>Cutibacterium acnes</i> (formerly known as <i>Propionibacterium acnes</i>) as surviving bacteria, among others. Immunofluorescence revealed bacteria in all skin layers. No participant exhibited clinical signs of infection in the abdominal region. Human data corroborated previous porcine data collected using destructive skin sampling after PSP. <b>Conclusions</b>: Clinical PSP application does not create a sterile field. Destructive skin sampling techniques may be more effective than ASTM E1173-15 at resolving bacterial PSP survivors contributing to SSI risk.