Antimicrobial metallic copper surfaces kill Staphylococcus haemolyticus via membrane damage

Area of Science:

• Microbiology
• Materials Science
• Biochemistry

Background:

• Metallic copper (Cu) shows promise for reducing contamination in healthcare settings.
• Understanding the antimicrobial mechanisms of Cu is vital for its effective application.
• Previous studies suggested various modes of action for Cu's antimicrobial properties.

Purpose of the Study:

• To elucidate the molecular mechanisms by which metallic copper inactivates the Gram-positive bacterium Staphylococcus haemolyticus.
• To determine the primary cellular targets responsible for copper-induced cell death.

Main Methods:

• Exposure of Staphylococcus haemolyticus to metallic copper and stainless steel surfaces.
• Inductively coupled plasma mass spectroscopy (ICP-MS) for ion analysis.
• In vivo staining with Coppersensor-1 and live/dead staining.
• Mutation rate analysis.

Main Results:

• Staphylococcus haemolyticus was rapidly killed on copper but not stainless steel, confirming copper's antimicrobial efficacy.
• Cells accumulated significant amounts of copper ions from metallic surfaces, indicating ion uptake.
• Live/dead staining revealed substantial cell membrane damage in copper-exposed cells.
• Mutation rates were similar in cells exposed to copper or stainless steel, ruling out genotoxicity.

Conclusions:

• Metallic copper kills Staphylococcus haemolyticus primarily through cell membrane damage, not DNA damage.
• Copper ions are taken up by cells, contributing to lethal damage.
• The cell membrane is the critical target for metallic copper's antimicrobial action.