Implementation and Evaluation of Environment-Derived Dust-Based Environmental Health Monitoring in an Open-Top Housing Laboratory Animal Facility.

Environmental health monitoring (EHM) has gained attention as a sensitive, animal-free alternative to soiled bedding sentinel (SBS) programs for microbiologic surveillance in laboratory animal facilities. Although several EHM approaches have been validated in facilities using IVC systems, empirical evidence supporting room and equipment monitoring (REM) remains limited, particularly in open-top housing environments. This study evaluated the feasibility and practical applicability of environment-derived dust-based REM in an open-top housing facility using open-top cages and open racks. Microbial capture at room exhaust outlets was first assessed by culture-based analysis of exhaust prefilters in mouse, rat, and rabbit rooms. In parallel, exhaust louver-derived dust (ELD) was collected from downstream exhaust duct louvers and analyzed by PCR. To enable more frequent and standardized sampling, floor-derived dust (FDD) was collected using robotic cleaning devices and subjected to PCR analysis. The impact of robotic cleaning on environmental hygiene and welfare was evaluated using ATP-based cleanliness testing and noise measurements. Environmental microorganisms were consistently captured on exhaust prefilters, including in rooms without animals. PCR-based testing successfully detected microbial nucleic acids in both ELD and FDD samples across multiple facility zones, demonstrating the feasibility of REM in an open-top housing system. Robotic-based dust collection provided sufficient material for repeated testing under routine facility operation, without compromising environmental cleanliness or exceeding acceptable noise levels. These findings suggest that environment-derived dust-based REM can be implemented as a facility-level surveillance approach in open-top housing facilities, offering an animal-free, time-integrated monitoring strategy aligned with the principles of the 3Rs (Replacement, Reduction, and Refinement).