Lavage with at least 2.5 mL/cm sterile saline reduces bacterial load in a subcutaneous tissue model.

Objective: To quantify the volume of lavage required to decrease the bacterial load below a standard of 105 CFUs/mL on a subcutaneous tissue model.

Methods: This was a benchtop experimental study conducted between May 1, 2023, through July 31, 2023 that included 20 sterile silicone skin models with a 10-cm incision. The silicone skin model was inoculated with a 1,000-fold dilution of approximately 1.5 X 108 CFUs/mL of isolated Staphylococcus pseudintermedius or Escherichia coli. Bacterial quantification samples were taken preinoculation, 20 minutes postinoculation, and after incremental saline lavage to total a volume of 2.5, 5, and 10 mL/cm incisional length bacterial quantification.

Results: For S pseudintermedius and E coli, a reduction of bacterial colonies below 105 CFUs/mL was noted in all lavage volumes, with an initial 3-log decrease from postinoculation to the 2.5 mL/cm lavage for both S pseudintermedius and E coli. Microbial growth demonstrated a 1-log reduction with increased lavage volumes from 2.5 mL/cm to 10 mL/cm for S pseudintermedius. For E coli, microbial growth demonstrated a 1-log reduction with the second lavage (total of 5 mL/cm) and a half-log reduction with the third lavage (total of 10 mL/cm).

Conclusions: Surgeons should consider a minimum of 2.5 mL/cm lavage when aiming to decontaminate SC tissues in linear surgical wounds. Further work in clinical cases is required to evaluate differences in live tissue compared to this model.

Clinical Relevance: This work provides surgeons with a reference point for deciding what volume of lavage to use for purposes of decontaminating an SC space.