Effect of TNP on the microbiology of venous leg ulcers: a pilot study

To investigate the effect of topical negative pressure, delivered using Vacuum Assisted Closure (VAC, KCI), on the microbiology of chronic, non-infected venous leg ulcers (VLUs).

Patients receiving compression therapy for a chronic VLU were recruited into this prospective pilot study. The ulcer was swabbed and VAC was applied at 125mmHg continuous sub-atmospheric pressure on day 1 for six days. Standard methods for bacteriological sampling and measuring the wound surface area were applied at baseline and at the VAC dressing changes on days 3 and 6. Log median colony forming units (CFUs) per cm2 were used for statistical analyses. The bacterial species were identified.

Seven patients were recruited into and completed the study. The median log10 CFU/cm2 on days 1, 3 and 6 were 3.5, 4.7 and 5.1 respectively. There was a significant increase in bacterial colonisation between days 1 and 6 (p<0.02). No change was observed in the identified microbiological species during therapy with VAC.

This pilot study suggests that VAC therapy increases absolute numbers of bacteria colonising non-infected leg ulcers.

KCI supplied the VAC equipment and ARANZ the SilhouetteMobile, but both had no other influence on the study.