A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus

J Biomed Mater Res. 2000 Dec 15;52(4):662-8. doi: 10.1002/1097-4636(20001215)52:4<662::aid-jbm10>3.0.co;2-3.

Abstract

To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO(3) and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag(+) treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag(+) treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag(+) ions.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / analysis
  • Bacterial Proteins / drug effects*
  • Cell Wall / drug effects*
  • Cell Wall / ultrastructure
  • Cytoplasmic Granules / ultrastructure
  • DNA Replication / drug effects*
  • DNA, Bacterial / analysis
  • DNA, Bacterial / drug effects*
  • Electron Probe Microanalysis
  • Escherichia coli / chemistry
  • Escherichia coli / drug effects*
  • Escherichia coli / ultrastructure
  • Microscopy, Electron
  • Silver / analysis
  • Silver Nitrate / pharmacology*
  • Staphylococcus aureus / chemistry
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / ultrastructure
  • Sulfur / analysis

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA, Bacterial
  • Silver
  • Sulfur
  • Silver Nitrate