The ability of a colloidal silver gel wound dressing to kill bacteria in vitro and in vivo

Inhibiting bacterial biofilms is of major significance for proper wound healing. The choice of the dressing material plays a key role, as bacteria can live in dressings and keep reinfecting the wound. This study examines the effectiveness of a colloidal silver gel (Ag-gel) wound dressing in inhibiting the growth of bacteria in a mouse wound model.

Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and two different meticillin-resistant Staphylococcus aureus (MRSA) strains were examined. Bacteria were measured in vitro on the dressing, and in vivo studies were carried out to analyses both the dressing and the infected tissue.

Using colony-forming unit (CFU) assays, over 7 logs of inhibition (100%) were found for Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii for the Ag-gel dressing when compared with the control dressing. In vivo, complete inhibition was observered for the three most common bacteria on the Ag-gel dressing and the tissue under that dressing. These results were confirmed by an in vivo live imaging system. However, with MRSA strains, only 2-3 logs of inhibition were recorded.

The Ag-gel was effective in preventing biofilm infections caused by both Gram-negative and Gram-positive bacteria.