Impact of Brush Materials and Design on the Attachment and Survival of Enterococcus faecium on Waxing Roller Brushes

Waxing roller brushes are made with different materials and arranged onto the brush core with various designs. Despite the widespread use of roller brushes, the impact of brush materials and design on the attachment and persistence of microorganisms remains largely uninvestigated. In this study, four types of brush coupons made with nylon or 50% polyethylene/50% horsehair [50/50] in spiral or tufted patterns were purchased from commercial brush suppliers. They were dip-and-roll inoculated with ∼8 log CFU/mL of Enterococcus faecium (EF). The relative liquid inoculum mass gain and the attached EF populations on brushes after inoculation, as well as after 48 h of drying, were studied. The survival of EF during a 90-day ambient storage was also monitored. Results showed that tufted brushes retained approximately 25% more relative liquid inoculum mass gain than spiral brushes, regardless of brush material. After 48 h of drying, the relative inoculum mass gain decreased significantly on all brush types to ca. 1%. The surviving EF after drying on tufted-nylon, spiral-nylon, tufted-50/50, and spiral-50/50 brushes were 7.06, 5.21, 8.24, and 7.54 log CFU/coupon, respectively, with the greatest EF reduction observed on spiral-nylon brushes. During the 90-day storage, tufted-50/50 brushes consistently harbored the highest EF populations, while spiral-nylon brushes had the lowest. Results demonstrated that both brush design and brush materials affected EF retention and survival. While the tufted design retained more bacterial inoculum than the spiral design, the 50/50 material supported higher bacterial survival initially and during storage. Fiber length, bristle density, as well as the surface structures of natural and synthetic fiber all contributed to the differences observed. This project fills critical knowledge gaps regarding the impacts of brush design and choice of brush materials on food safety and lays the foundation for risk assessment of waxing roller brushes.