Figure 1

Individual differences in hand antimicrobial activity and the importance of surface components. (A) Qualitative comparison results using agar medium for (a) hands with high antimicrobial activity and (b) hands with low antimicrobial activity. Results for 30 s (control) and 3 min after applying E. coli (OD = 0.2) on the hand. (B) Correlation between the antimicrobial activity on the hands (in vivo) and the antimicrobial activity of the surface components on the hands (in vitro). The antimicrobial activity on the hands was measured by applying an E. coli solution (OD = 0.2) for 3 min. The surface components of the hands were collected with a cotton swab, and concentrated to 0.8 μL/cm² using DMSO. The antimicrobial activity was measured by mixing the sample with equal amounts of E. coli (OD = 0.02) and by allowing it to produce a reaction for 30 min. The log reduction value denotes the relative logarithmic reduction of viable bacteria. The value of Pearson’s correlation coefficient is indicated in the graph. (C) Correlation of the antimicrobial activity of the surface components on the hands against E. coli, S. aureus, and influenza A virus. Symbols with the same color indicate individual participants (S1–S6) between the three graphs. E. coli, S. aureus, and influenza A virus were evaluated using undiluted samples, eightfold diluted samples, and 100-fold diluted samples, respectively, due to the toxicity of DMSO. The log reduction value denotes the relative logarithmic reduction of the bacterial or viral number. The value of Pearson’s correlation coefficient is indicated in each graph.