Correlation between antibacterial activity and crystallite size on ceramics

► We prepared MgO and ZnO powder samples having different crystallite sizes. ► We examined the antibacterial activity toward Escherichia coli and Staphylococcus aureus. ► Antibacterial effect was different between Escherichia coli and Staphylococcus aureus. ► Irrespective of kinds of powder samples, a smaller crystallite size showed greater antibacterial activity. ► We clarified that the antibacterial activity of MgO and ZnO powder samples was dependent on the crystallite size.