Antibacterial Effects of Silver Electrodes with Weak Direct Current

Silver, platinum, gold, stainless-steel, and copper electrodes were used with low currents (0.02 to 20 muA/mm(2)) to explore their electrochemical effects on the growth of four bacterial species. In the higher current ranges, all electrodes inhibited growth at both poles, usually in conjunction with electrolytic break-down of the medium and severe corrosion of the metal. Silver, however, was extremely bacteriostatic, even at the lowest current, when used as the anode. Quantitative studies showed that most of this inhibition takes place in a few hours and is not accompanied by changes in pH. Electrochemically injected silver from the anode is probably the instrumental agent, being effective in concentrations of about 5 mug/ml. This is the equivalent concentration of silver sulfadiazine that has been shown to give complete inhibition of bacteria, but without the sulfonamide moiety.