Abstract
Staphylococcus aureus is well detected on affected area of atopic dermatitis (AD). Akiyama et al. reported that zinc oxide (ZnO) powder is effective in the medical treatment of AD. Although the ZnO powder has been found to show strong antibacterial activity, the difference of susceptibility between strains of S. aureus and other bacteria inhabiting normally on human skin has not been studied. In this study, we investigated the antibacterial activity of the ZnO powder against 20 strains of human skin-normal bacteria including S. aureus. Ten strains of S. aureus and ten strains of other skin-normal bacteria were exposed to the ZnO powder slurry (0.006-50 mg/ml) and examined for their antibacterial activities by the conductimetric assay, in which the conductivity change caused by bacterial metabolism was detected. The kinetic parameters and Minimum Inhibitory Concentration (MIC) could be determined by the application of the inhibition kinetic model proposed by Takahashi for calorimetric evaluation. Kd indicates affinity between the ZnO powder as antibacterial regent and bacterial cells, and the affinity gets bigger when the Kd value decreases. MIC tended to be lower while Kd decreased (R2=0.89), indicating that the antibacterial activity got higher with increasing of the affinity.
