Biofilms in shower hoses – choice of pipe material influences bacterial growth and communities

Abstract

Flexible polymeric pipe materials are commonly used as shower hoses or connections to faucets in the last meters of building plumbing, but these tend to leach high concentrations of carbon that encourage bacterial growth. Here we compared the microbiological impact of six such materials, with both a short-term material comparison test and a daily shower simulator operating for eight months. The materials ranked differently in the migration potential and biomass formation potential assays of the comparison test, but overall these results correlated (R² > 0.77) with long-term biofilm development in the shower simulator. The biofilm concentration after eight months ranged from 2 × 10⁶ cells per cm² on the control material (PE-Xc) to 2 × 10⁸ cells per cm² on a typical shower hose (PVC-P). However, the differences in four of the six materials were much less pronounced after eight months than in the early months. The communities were characterized with 16S rRNA amplicon sequencing clustered with both material and time (R² = 0.31; R² = 0.25), and correlated strongly with the biofilm concentration (R² > 0.74). A universal core consisting of 7 genera accounted for 44% of all sequences, and accounted for more of young and high-biomass biofilms. Genera containing opportunistic pathogens were more common in low-biomass pipes. We conclude that choice of materials is not only critical for determining biofilm concentration, but also community composition. Our results show that a seemingly small choice in plumbing material in the final meters of distribution can make a considerable difference in the building plumbing ‘exposome’.