Detailed Analysis of Surface Infection Barrier on Hands: Relationship with Morbidity to Infection Diseases and Identification of Antimicrobial Components

Although the surface of hands in humans is known to harbor high levels of antimicrobial activity, reports investigating the relationship between antimicrobial activity and morbidity in infectious diseases are lacking. Additionally, the precise components involved in this activity are not known. Therefore, in this study, a method was developed to quantitatively measure the antimicrobial activity of the components found on the surface of hands, which was then compared with the medical history of the participants for infectious diseases. As a result, the antimicrobial activity of the surface of the hands was found to be positively associated with the history of infection in individuals. Furthermore, a comprehensive analysis of the components on the surface of hands indicated that organic acids and antimicrobial peptides are highly correlated with antimicrobial activity. The high amounts of lactic acid found on the surface of hands suggested it is an important factor in the hand surface infection barrier. Here we showed that the application of lactic acid within the range of the amounts present on the hand surface was found to significantly improve the antimicrobial activity of the hands. Taken together, these results demonstrate that this new method can be used to quantify antimicrobial activity, which opens new avenues for the development of hand hygiene practices by enhancing the antimicrobial activity on the surface of hands using natural ingredients against pathogens.