Measuring the Maximum Effective Depth of Silver-Impregnated Fabrics and Biocidal Silver Against Staphylococcus epidermidis and Escherichia coli

The following project determined the maximum effective depth in wounds at which silver-impregnated fabrics exhibit antimicrobial properties. Two different fabrics were tested in this study: an electrolessly plated silver nylon fabric and commercial silver nylon fabric marketed as Silverlon. Slant-agar plates composed of Mueller-Hinton II agar were utilized to test these fabrics and measure the maximum depth at which the silver dressings remain effective against Staphylococcus epidermidis and Escherichia coli. Concentrations of silver at the resulting zones of inhibition were determined by graphite furnace atomic absorption spectroscopy. Growth-curves and cell counts were established at varying concentrations of silver based on the results of the slant-agar plate studies. The results of this study have shown that both experimental and commercially bought silver wound dressings are effective at inhibiting the growth of Staphylococcus epidermidis and Escherichia coli. Average concentrations of silver present at the resulting zones of inhibition for S. epidermidis and E. coli were found to be 3.81 ppm and 7.59 ppm, respectively. Growth curve studies for S. epidermidis showed a slight increase in the slope of the logarithmic growth portion of the curve, indicating a promotion of growth as a result of silver exposure. Growth curve studies for E. coli showed a decrease in the slope of the logarithmic portion of the curve, indicating an inhibitory effect as a result of silver exposure