LeCo - Legionella control in buildings

Legionella spp. are gram-negative bacteria that are ubiquitously present in the environment. Water and soil are the main natural reservoirs. When bacteria-contaminated aerosols are inhaled, Legionella can cause a severe form of pneumonia called Legionnaires’ disease (LD). Cases of LD in Switzerland are becoming more common, reaching an annual incidence of 6.8 cases per 100'000 population in 2019. The main sources of infection for LD remain unknown.

In response to the growing number of LD cases, the LeCo project (Legionella control in buildings) was launched at the beginning of 2020. The project is investigating (i) how the occurrence of Legionella bacteria in the environment is related to human infection, (ii) how Legionella spp. is best detected in the environment and (iii) how control measures of Legionella growth within the plumbing system can be optimised. The consortium consists of a multidisciplinary team from Eawag, the Lucerne University of Applied Sciences and Arts, the Swiss TPH and the Cantonal Laboratory Zurich. The LeCo project is jointly funded by the Federal Food Safety and Veterinary Office (FSVO), the Federal Offices of Public Health (FOPH) and the Federal Offices of Energy (FOE).

Tracing the source for a clinical Legionella spp. infection in the environment is challenging due to the ubiquitous nature of the bacteria. To confirm an infection source genomic comparison of Legionella strains isolated from LD patients and the environment is required. Swiss TPH and its LeCo consortium research partners are now assessing the feasibility and applicability of Whole Genome Sequencing (WGS) for the investigation of environmental infection sources of community-acquired LD. This assessment is done within the framework of a prospective, national case-control and molecular source attribution study (SwissLEGIO). This link to the SwissLEGIO project ensures timely access to environmental water samples from the patients' homes and allows a subsequent comparison of environmental Legionella spp. strains to clinical Legionella strains obtained from patients.

The research is part of a concerted effort to inform Swiss authorities and policymakers in human LD treatment and control, environmental management, energy and infrastructural engineering. Alongside the research aspects, the project hence also focuses on raising awareness and increasing communication among the various national and international stakeholders.

Stettler A. LeCo will Legionellen verstehen. Phase 5. 2021;1:34-39


Daniel Mäusezahl

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