EESS talk on "Detection of Legionella by culture methods and qPCR in building water systems: Is there a golden ratio?"


Event details

Date 24.05.2022 12:1513:15  
Speaker Dr Emile Sylvestre, Postdoctoral fellow, Department of Microbiology, EAWAG
Location Online
Category Conferences - Seminars
Event Language English
Culture-based and quantitative polymerase chain reaction (qPCR) methods can be used to detect the opportunistic pathogen Legionella in water from a variety of engineered systems. qPCR is a more rapid method than culture and can facilitate the implementation of remedial actions to reduce Legionella concentrations. However, results obtained with culture are typically required to evaluate compliance with regulatory action thresholds, limiting the applications of qPCR. To help interpret qPCR-generated data, we are conducting a meta-analysis to compare results obtained with the two methods (qPCR and culture) in various building water systems. So far, we have compiled about 1000 paired Legionella samples from the peer-review literature and Swiss laboratories. We also gathered system information (e.g., building type, water system, sampling strategy) for data interpretation and subgroup analyses. For each study, we quantify the mean qPCR/culture concentration ratio with descriptive statistics and mixed Poisson models. We then evaluate the pooled mean ratio with an inverse variance heterogeneity (IVhet) meta-analysis model. Preliminary results show that the between-study heterogeneity is high but mean concentrations are about ten times higher with qPCR than with culture on average. We are currently evaluating whether subgroup analyses can be undertaken to identify the main factors driving this ratio. This meta-analysis is a critical first step in developing a better understanding of how we can interpret qPCR-generated data and how current regulatory structures could be adapted to allow appropriate application of qPCR.

Short biography:
Dr Emile Sylvestre is a postdoctoral fellow at EAWAG in the department of Environmental Microbiology. Emile is from Montreal, Canada, where he did his bachelor and graduate studies in Civil Engineering at Polytechnique Montreal. He completed his Ph.D. thesis “Systematic assessment of microbial risks associated with hydrometeorological events for drinking water safety management” in 2020. As a research associate in the same group, he then collaborated with the Government of Quebec to develop and implement risk-based approaches for the management of Cryptosporidium in drinking water and Legionella in cooling towers. At EAWAG, Emile currently works on the development of risk-based monitoring approaches for the evaluation of Legionella in building water systems. He also investigates how to control enteric viruses in decentralized greywater treatment processes.

Practical information

  • General public
  • Free
  • This event is internal


  • EESS - IIE


  • Prof. Tamar Kohn, LCE


Legionella risk assessment environmental monitoring statistical modeling public health