This is an in vitro method where a 5ml suspension of organism is used to challenge a dressing containing an active over a specified time period. Six replicate pieces of 2 cm x 2 cm dressing are inoculated with 5x10⁵ CFU/ml of a relevant organism, to reflect a clinical situation. Samples are incubated under dynamic conditions at 32^oC for 0h and 24 h. The dynamic nature of the test ensures good contact with the bacteria and the dressing, whilst being emulative of movements in dressing wear. Following incubation, the dressings are removed and the resulting suspension neutralised to arrest the silver activity. Subsequently numbers of surviving bacteria remaining are assessed using standard microbiology techniques. The Log reduction for the test dressings is calculated by subtracting the mean value obtained for the control.

 In activity testing, an active such as silver may be considered cidal if it achieves log₁₀ reductions of 3 log₁₀ or greater. Both the Adhesive and Non-Adhesive formats of the silver hydrocellular foam dressing achieved mean log₁₀ reductions  greater than 3 log₁₀ CFU/sample within 24 hours against a broad spectrum of wound pathogens, including Gram positive and Gram negative bacteria, antibiotic resistant bacteria, anaerobes and yeast.