Antibacterial activity and mechanism of action of the silver ion in Staphylococcus aureus and Escherichia coli.
The antibacterial effect and mechanism of action of a silver ion solution that was electrically generated were investigated for Staphylococcus aureus and Escherichia coli by analyzing the growth, morphology, and ultrastructure of the bacterial cells following treatment with the silver ion solution. Bacteria were exposed to the silver ion solution for various lengths of time, and the antibacterial effect of the solution was tested using the conventional plate count method and flow cytometric (FC) analysis. Reductions of more than 5 log(10) CFU/ml of both S. aureus and E. coli bacteria were confirmed after 90 min of treatment with the silver ion solution. Significant reduction of S. aureus and E. coli cells was also observed by FC analysis; however, the reduction rate determined by FC analysis was less than that determined by the conventional plate count method. These differences may be attributed to the presence of bacteria in an active but nonculturable (ABNC) state after treatment with the silver ion solution. Transmission electron microscopy showed considerable changes in the bacterial cell membranes upon silver ion treatment, which might be the cause or consequence of cell death. In conclusion, the results of the present study suggest that silver ions may cause S. aureus and E. coli bacteria to reach an ABNC state and eventually die.
Jung
Woo Kyung
WK
Department of Microbiology, KRF Zoonotic Disease Priority Research Institute, College of Veterinary Medicine, Seoul National University, Sillim-dong, Gwanak-gu, Seoul 151-742, Korea.
Koo
Hye Cheong
HC
Kim
Ki Woo
KW
Shin
Sook
S
Kim
So Hyun
SH
Park
Yong Ho
YH
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000032:analysis / Q000187:drug effects*; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D012834:Silver / Q000032:analysis / Q000494:pharmacology*; D012835:Silver Nitrate / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012834:Silver; D012835:Silver Nitrate