Sustained Chlorination of Hospital Surfaces Restructures the Microbiome and Virome and Diversifies Resistance Genes

Routine disinfection can reduce microbial burden on hospital surfaces in the short term, but its long-term impacts on surface microbiomes and antimicrobial resistance dynamics remain unclear. We conducted a year-long metagenomic study of 197 in situ hospital surface samples subjected to sustained chlorination to investigate changes in microbiomes, resistomes, and phage-host interactions. Microbial α-diversity increased during the early months, with a decline in dominant Enterobacteriaceae and enrichment of taxa including Propionibacteriaceae and Micrococcaceae, indicating niche replacement. Over time, both diversity and previously suppressed taxa approached baseline levels, suggesting adaptation to sustained disinfection, with evidence of functional shifts. Viral communities exhibited similar temporal dynamics, with composition and relative abundance distinctly shifting. Concurrently, the resistome underwent substantial, largely irreversible restructuring, with decreased total relative abundance and increased diversity of antibiotic resistance genes (ARGs). Chlorination also reduced ARG mobility and pathogenic potential, indicated by weakened co-occurrence with mobile genetic elements and virulence factor genes and lower predicted resistome risks. Phage and host relative abundances remained strongly correlated, although a shift toward lytic viral lifestyles occurred, potentially limiting phage-mediated ARG dissemination. These findings highlight disinfection as both a microbial control measure and ecological pressure, underscoring the need for ecologically informed strategies to manage clinical antimicrobial resistance.