A-055. The Importance of ROS Generation on Antimicrobial Activity by Silver Ion

H-J. Park1, J. Kim1, J. Kim1, J-H. Lee2, J. Yoon1;
1Seoul Natl. Univ., Seoul, REPUBLIC OF KOREA, 2Pusan Natl. Univ., Pusan, REPUBLIC OF KOREA.

Silver ion has been widely used as antimicrobial agent. One of major bactericidal mechanism of silver ion has been generally known for interaction with thiol group of L-cysteine, the interaction interrupts essential enzymatic functions in microorganism. In addition, the effect of silver ion on perturbation of the respiratory chain in Escherichia coli has raised the hypothesis that silver ion may generate reactive oxygen species (ROS). ROS generates only in the presence of oxygen, however the oxygen effect on bactericidal activity of silver ion has not yet been demonstrated. In this study, we investigate the effect of ROS generated by silver ion on the bactericidal activity of silver ion. ROS effect by silver ion was excluded in anaerobic condition, and the antimicrobial activity was compared with the results of aerobic condition. Escherichia coli MS1343 (soxS::lacZ) strain was used. We confirmed the superoxide mediated stress by silver ion through the detection of superoxide inducible gene (soxS) induction. In the presence of oxygen, silver ion at low concentration (≤ 1 mg/L) definitely increased bactericidal activity as compared with the absence of oxygen. Silver ion showed 2-3 fold greater log reduction in the presence of oxygen as compared with the absence of oxygen, suggesting that more than half of E. coli inactivation was occurred by ROS in silver disinfection. This result indicates that the ROS generated by silver ion plays an important role in antimicrobial activity. Therefore, disinfection system using silver ion should be considered the oxygen concentration.