Characterization of Microbial Communities on the Surfaces of Building Entrance and Restroom Door Handles

This study investigated the microbial contamination and community composition on door handle surfaces in public buildings with high pedestrian traffic Door handles from four buildings (A, B, C, and D) were sampled at both the indoor and outdoor sides of the main entrances and restrooms. By evaluating microbial contamination and community composition, this study aimed to provide an objective assessment of hygiene conditions in public facilities and to offer foundational data for improving public hygiene management. Microbial activity was assessed by measuring ATP (Adenosine triphosphate)-based RLU (Relative Light Units). Microbial concentration and community distribution were evaluated through CFU (Colony Forming Unit) counts and DGGE (Denaturing Gradient Gel Electrophoresis) in two buildings (A and B) where pedestrian flow remained stable during the observation period. The sample showing the highest DGGE band diversity was further analyzed using 16S rRNA amplicon sequencing–based metagenomics to determine detailed microbial community composition. The results showed that buildings with higher pedestrian flow exhibited increased surface contamination. For example, Building D recorded the highest foot traffic (192.3±3.1 people h⁻¹), while the restroom door in Building A exhibited the highest ATP level (1,411.7±789.6 RLU) on the indoor handle. Microbial concentrations also varied between indoor- and indoor handle surfaces, depending on both contact frequency and building environmental factors—such as lighting and ventilation. DGGE analysis revealed distinct differences in microbial community structure among the samples, while metagenomics indicated the presence of potentially pathogenic bacteria in the samples. Overall, this study confirms that microorganisms on door handles are influenced by pedestrian traffic, touch frequency, and environmental conditions. These findings underscore the importance of regular cleaning and disinfection of frequently touched surfaces and suggest that implementing non-contact door-opening systems could reduce cross-contamination and improve hygiene in public indoor environments.