From clean to colonized: microbial dynamics of bed linen over time.

Bed linen can act as a reservoir for microorganisms transferred from skin, dust, and the environment. Despite the importance of linen hygiene in healthcare and hospitality, evidence on bed-changing frequency is limited, with studies reporting only cross-sectional microbiological data. This study investigated longitudinal bacterial and fungal colonization of bed linen over 4 weeks in a domestic environment. Nine participants used polycotton bed linen for 1 day to 4 weeks. Swatches were collected from the pillow, hip, and foot regions, analyzed using viable counts and amplicon-based sequencing. After use, bacterial and fungal loads increased, respectively, from 3.61 log₁₀CFU/25 cm² and 3.25 log₁₀CFU/25 cm² at day one to 3.96 log₁₀CFU/25 cm² and 3.63 log₁₀CFU/25 cm² after one week. Loads remained stable over four weeks (bacteria > 3.9 log₁₀; fungi > 3.5 log₁₀CFU/25 cm²). Amplicon-based sequencing showed that 65% of samples were dominated by Staphylococcus spp. (50%-99% relative abundance), with S. capitis, S. hominis, and S. epidermidis most frequent. Fungal communities varied but commonly included Naganishia spp., Candida spp., and Penicillium spp. These findings demonstrate rapid microbial accumulation on bed linen, which remains stable over a month. Although based on a small domestic cohort, the microbial burden suggests a potential role for bed linen in exposure risk, supporting the need to consider bed-changing practices.