Hospital Drain Microbiomes as Distinct Microbial Signatures Within Urban Wastewater Networks in the Han River Watershed

Background: Hospital drainage systems represent an important interface between healthcare facilities and urban wastewater networks and may contribute distinct microbial inputs to downstream aquatic environments. This issue is particularly relevant in Seoul, Republic of Korea, where urban wastewater discharges into receiving waters within the Han River watershed. Methods: In this study, we characterized hospital drain microbiomes to evaluate their microbial and environmental signatures, using residential drains as a non-clinical comparison. Results: Hospital drains exhibited a distinct taxonomic profile, with greater relative abundances of Bacteroidota and Firmicutes and several genera of environmental or potential public health relevance, including Mycobacterium, Legionella, and Pseudomonas. Although microbial richness was comparable between the two environments, Simpson diversity was significantly lower in hospital drains, indicating reduced community evenness. Bray–Curtis and Jaccard analyses showed clear separation between hospital and residential microbial communities, and hierarchical clustering further supported environment-associated community structuring. LEfSe analysis identified distinct hospital-associated taxonomic biomarkers, and predicted functional profiling revealed substantial metabolic differentiation, with 19 of the 25 most significantly differentiated pathways enriched in hospital samples. Conclusions: These microbial and functional differences underscore the ecological uniqueness of hospital drains and support their inclusion in future wastewater-based microbial surveillance strategies. Collectively, these findings establish hospital drains as distinct microbial ecosystems within urban wastewater networks and provide a baseline for future studies examining the persistence of hospital-associated microbial signatures within the Han River watershed.