Department Environmental Microbiology

Pathogenic species of the gram-negative bacterial genus Legionella are the causative bacterial agents of legionellosis. Building plumbing systems are a known source of legionellosis cases, as they can provide favorable conditions for the bacterium’s growth. In Switzerland, where chlorination is not used, temperature control is the main strategy to prevent Legionella. Temperature has a direct effect on Legionella growth (25 and 45 °C) and viability/death (> 50 °C).

When taps and shower hoses are not used, the water stagnates in the pipes. As stagnation time increases, temperature decreases, leading to conditions favorable to Legionella growth. Stagnation of water is omnipresent in building plumbing and it can span seconds to months. It is expected that different stagnation times will lead to different outcomes in terms of the effect on Legionella.

As part of the LeCo project (Legionella Control in Buildings), my PhD research will focus on understanding the impact of water stagnation and temperature fluctuations on survival, selection and proliferation of Legionella as well as the associated plumbing microbiome. To this end, I will do experiments at the lab scale, pilot scale and building scale. The outcome of this research will inform best practices on Legionella control in the absence of disinfectant residuals.