- This study opens the investigation series focused on antimicrobial effects of copper (Cu) compared to silver (Ag), which is currently used to treat wound infection in burn victims as well as in chronic wounds. Noticeably, in its ionized state, Cu is more commonly present as Cu2+ rather than as Cu+, while electronic configuration similarity of Cu+ and Ag+ indicates that actually it may be the active state. To test this hypothesis, effect of Cu+ and Cu2+, using Ag+ ions and metallic copper as controls on Escherichia coli and Staphylococcus aureus bacteria, was examined under anaerobic conditions. Cu+ was produced by two different methods, and its effect on microorganism growth was tested using a syringe and Petri dish methods. It was found that the presence of Cu+ causes a dramatic depletion in the viability of both microorganisms. Metallic copper did not have any effect on the viability, whereas Cu2+ and Ag+ ions had much lower activity than Cu+ ions. Minimal inhibitory concentration of Cu+ for E. coli was twice lower than that of Cu2+. The obtained results show that Cu+ proves to be a potent antimicrobial agent.