Evaluating the impacts of synthetic and natural indoor surface finishes on the microbiome

Project Goal The goal of this project is to evaluate how surface finishes impact the indoor microbiome and resistome. Objectives To reduce the carbon footprint of buildings, we are increasingly using “natural” or “carbon-neutral” building materials, e.g., clay paints and plasters. These replace synthetic paints, which are often embedded with antimicrobial chemicals to prevent their degradation and inhibit the spread of pathogenic microbes. However, the efficacy of these antimicrobials is unproven and they may in fact have negative impacts, such as increasing the abundance of antibiotic resistance genes in the indoor microbiome, thus putting inhabitants at a greater risk of contracting an antibiotic-resistant infection. Clays have been used in other contexts as antimicrobial agents; however, the effect of clay surface finishes on the indoor microbiome are unknown. The objectives of this project are to evaluate the effects of conventional antimicrobial paints, clay paints, and clay veneer plasters on culture isolates of known indoor bacteria by measuring changes in viability and antibiotic resistance as a function of humidity. These objectives will feed into a larger program of research to include modeling as well as evaluation of microbial ecology and antibiotic resistance in real-world buildings containing different surface finishes. Proposed Activities Funding from this grant will be used to conduct empirical research to evaluate antimicrobial activity of conventional and natural paints. This research consists of bench-scale experiments to examine changes in the viability and phenotype of bacterial strains common to the built environment. Briefly, sample-sized coupons of paperless drywall will be prepared with one of each of the following, selected with the input of practitioners in the field: conventional antimicrobial paint, clay paint, clay veneer plaster, conventional non-antimicrobial paint as the control. Coupons will be inoculated with bacterial strains isolated from indoor dust. After incubation for 6 days, the bacteria will be cultured and their viability and sensitivity to antibiotics will be assessed. In addition, physical and chemical properties of the finishes, including porosity and moisture content, will be measured. Expected Products This project is expected to yield several products including one peer-reviewed publication, multiple presentations at both scientific and industry meetings, contributions to multiple Wikipedia entries to reflect current knowledge and practice, and coverage in the popular press (aided by the PI’s formal media training and existing contacts). Expected Outcomes The outcomes of this project will be the generation of new knowledge regarding the effect of paints and plasters on the indoor microbiome and enhanced public understanding through Wikipedia and the press. It will also lay the foundation for a new research program, integrating materials science, chemistry, and microbiology. Federal and other funding for this new program will be pursued using preliminary data from this study.