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

OBJECTIVE: 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. METHOD: 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. RESULTS: 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. CONCLUSION: The Ag-gel was effective in preventing biofilm infections caused by both Gram-negative and Gram-positive bacteria.

Efficacy of a silver colloidal gel against selected oral bacteria in vitro.

Background: It is necessary to develop new strategies to protect against bacteria such as S treptococcus mutans, S treptococcus sanguis, and Streptococcus salivarius, which contribute to tooth decay and plaque formation. Our current study investigated the efficacy of a colloidal silver gel in inhibiting biofilm formation by these principal oral bacteria , in vitro. The aim of this study was to assess the efficacy of a colloidal silver gel formulation for inhibiting bacterial biofilm formation (Ag-gel) by the principal bacteria that cause plaque formation and tooth decay. Methods: The effect of Ag-gel on viability of S. mutans, S. sanguis, and S. salivarius was assessed by quantifying their colony forming units (CFU) in presence or absence of the test gel. The effect of this formulation on biofilm-forming ability of these bacteria was studied through scanning electron microscopy. Results: Using the CFU assays, over 6 logs of inhibition (100%) were found for S. mutans, S. sanguis, and S. salivarius for the Ag-gel-treated bacteria when compared with the control gel. In addition, the Ag-gel also inhibited biofilm formation by these three bacteria mixed together. These results were confirmed by scanning electron microscopy. Conclusions: The Ag-gel was effective in preventing biofilm formation by S. mutans, S. sanguis, and S. salivarius. This Ag-gel should be tested for the ability to block plaque formation in the mouth, through its use as a tooth paste.