Antibacterial characteristics of magnesium oxide powder

The antibacterial activity of magnesium oxide (MgO) was studied. Inhibitory zones appeared around the MgO powder slurry put directly on nutrient agar plates seeded with Escherichia coli or Staphylococcus aureus. However, no zone was observed using a penicillin cup to avoid contact between the bacteria and the MgO powder. Moreover, the supernatant solution of the MgO powder slurry and a MgCl₂ solution containing Mg²⁺ at a concentration of the solubility of MgO did not affect the growth of E. coli and S. aureus. Moreover, elevated shaking speed increased the death of E. coli in the slurry, indicating that the contact frequency between bacterial cells and MgO powders affected the antibacterial activity. It was considered that the contact between MgO powder and bacteria was important for the occurrence of its antibacterial activity. Since the generation of active oxygen, such as O₂ ^–, from the MgO powder slurry was detected by chemiluminescence analysis, an investigation was carried out to determine whether active oxygen generated from MgO powder slurry was related to its antibacterial activity. The changes in the antibiotic sensitivity in E. coli treated by MgO powder agreed with those by active oxygen treatment. These results suggested that the active oxygen generated from the MgO powder slurry was one of the primary factors in its antibacterial activity.