Bacterial burden and wound outcomes as influenced by negative pressure wound therapy 

Abstract: Negative pressure wound therapy (NPWT) has consistently shown significant clinical benefits in wound healing, but the mechanisms are not fully elucidated. While a reduction in bacterial burden is one possible contributor, studies have shown mixed results in this regard. The present study used a porcine infected wound model to test the effect of NPWT on bacterial burden.

Infected wounds (Pseudomonas aeruginosa, coagulase negative Staphylococcus, and Bacteroides fragilis) in a porcine model were treated with V.A.C.® therapy with the standard GranuFoam™ dressing, V.A.C. therapy with the GranuFoam Silver® dressing, or moist gauze for a period of 7 days with three dressing changes. Quantitative and semiquantitative bacterial cultures, histological samples, and digital photographs were taken at dressing changes.

The wounds continued to show gross and microscopic improvement when treated with standard NPWT and NPWT with silver compared to moist wound care controls. However, the bacterial burden in all wounds continued to increase and broadened to include local skin flora, which had been absent immediately after wounding. These increases in bacteria were not affected by the use of silver dressings.

Negative pressure wound therapy with either standard NPWT foam or silver NPWT foam produced significant improvements in local wound appearance. This occurred despite a persistently high level of bacterial infection; thus, the improvement in healing of these infected wounds cannot be explained by a change in the bacterial burden. .