Ph.D. Student, Polytechnique Montréal
Margot Cazals is a Ph.D. student under the NSERC Industrial Chair on Drinking Water at Polytechnique Montréal. After a master’s degree project on the enzymatic rapid online detection of fecal contamination in recreational waters, she started a Ph. D. project on the microbial diversity in drinking water distribution systems. Her project aims to identify design, operational and management strategies allowing a control of the proliferation and persistence of opportunistic pathogens such as Legionella pneumophila in these systems. In her presentation, Margot will present results of a pilot scale study on the impact of plumbing materials and temperature on the integration of environmental strains of Legionella pneumophila in drinking water biofilms.
Impact of Temperature and Plumbing Material on the Integration of Environmental Strains of Legionella pneumophila in Drinking Water Biofilms
Abstract: Biofilm formation on pipe surfaces of drinking water systems is a leading cause of waterborne illnesses, especially in high-risk settings such as health care facilities. Biofilms are complex microbial communities that are known reservoirs of human pathogens, such as Legionella pneumophila (Lp). A six-month pilot study was conducted using 12 CDC reactors operated intermittently to evaluate the impact of temperature (25°, 40°, 55° and 60° C), stagnation and pipe material (polypropylene, polyvinyl chloride, EPDM rubber, cross-linked polyethylene, stainless steel and copper) on the composition of natural drinking water system biofilms and on their ability to integrate Lp in the presence of a host, Vermamoeba vermiformis (Vv).
All reactors were operated with tap water for several months before seeding with Vv and then Lp. Reactors with copper were set to 55 and 60° C (simulating hot water systems) and 40° C (simulating mixing valve). Scanning electron microscopy, flow cytometry (bulk bacteria and hosts), Legiolert and qPCR technologies were used to monitor the survival of Lp and Vv in the biofilm and bulk phases. Clear differences in density and microbial composition of biofilms were observed between materials and in response to the thermal changes. A transfer of Lp from biofilms to water was observed with increasing temperature, resulting in Lp concentrations sufficient to cause potential infections.