# Microbial landscape: composition and health associations of environmental microbiome in key functional spaces of premium elderly care facilities

## TL;DR

This study shows that bacteria in elderly care facilities vary by room type and are influenced by factors like humidity, suggesting tailored cleaning and environmental controls could improve resident health.

## Contribution

The study provides a detailed characterization of the environmental microbiome in premium elderly care facilities and identifies space-specific microbial patterns and health implications.

## Key findings

- Dining areas and recreational rooms have higher microbial richness and human-associated taxa like Firmicutes.
- Medical facilities and bathrooms have lower diversity but more opportunistic pathogens like Pseudomonas and Klebsiella.
- Relative humidity and occupancy are key environmental drivers of microbial community structure.

## Abstract

The environmental microbiome in elderly care facilities plays a crucial role in the health of aging populations with immunosenescence; however, its composition and health associations remain underexplored. This study characterizes the microbial ecology of premium elderly care facilities, focusing on key functional spaces, environmental drivers, and implications for resident health. We conducted 16S rRNA gene sequencing (V3–V4 regions) on 320 surface and air samples from six functional spaces (dining areas, medical facilities, bedrooms, bathrooms, recreational rooms, and corridors) across four premium elderly care facilities. Environmental parameters (temperature, humidity, CO₂, and occupancy) were measured concurrently. Bioinformatics analysis (QIIME 2, DADA2, and Silva database) and statistical modeling (permutational multivariate analysis of variance, distance-based redundancy analysis, and PICRUSt2) were employed to assess microbial diversity, taxonomic composition, functional potential, and environmental correlations. Using 16S rRNA gene sequencing across four facilities in different geographic regions, we identified significant spatial heterogeneity in microbial diversity and composition, with dining areas and recreational rooms exhibiting higher richness (Shannon index: 6.07 ± 0.37) and human-associated taxa (e.g., Firmicutes), while medical facilities and bathrooms harbored lower diversity but elevated opportunistic pathogens (Pseudomonas and Klebsiella). Environmental parameters—particularly relative humidity (explaining 13.8% of community variation) and occupancy—strongly influenced the microbial structure. A core microbiome dominated by Proteobacteria, Firmicutes, and Actinobacteria was conserved across facilities, while functional predictions revealed space-specific traits, including predicted enrichment of antibiotic resistance genes in medical facilities (ARG Shannon diversity: 4.87 ± 0.42) and carbohydrate metabolism pathways in dining areas. Negative correlations between beneficial (Lactobacillus) and pathogenic taxa (Staphylococcus aureus) were consistent with potential ecological strategies for microbial balance, although validation with absolute quantification is needed. This study highlights the need for space-specific microbial management in elderly care environments, emphasizing humidity control, ventilation, and targeted hygiene to mitigate pathogen risks while preserving beneficial communities. Our findings suggest the potential value of ecologically informed stewardship over pathogen-centric approaches. Future research should integrate multi-omics and longitudinal health data to optimize microbiome-resident health interactions.

As people age, their immune systems weaken, making the elderly especially vulnerable to germs in their surroundings. This study reveals that the types and amounts of bacteria living on surfaces and in the air within premium elderly care facilities differ significantly depending on the room's purpose—such as dining areas, medical rooms, or bathrooms. We found that humidity and how many people use a space strongly influence these bacterial communities. Crucially, areas like medical rooms had more bacteria linked to infections and antibiotic resistance, while social spaces hosted more diverse and potentially beneficial bacteria. This shows that a “one-size-fits-all” cleaning approach is not ideal. Instead, tailoring hygiene practices and environmental controls (like managing humidity) to specific spaces could better protect residents' health by reducing harmful germs while supporting helpful ones, offering a smarter way to manage these critical living environments for our aging population.