Action plans

Management of facilities at risk

Risk control by facilities managers is a complex problem that requires joint consideration of multiple parameters, such as changing the installation or its operation, the implementation of integrated treatments and monitoring physio-chemical and microbiological specific parameters.

Fighting against legionella means using biocides, from which the efficiency against bacteria, algae and protozoa has been demonstrated, but also simultaneously attacking the main factors favoring their growth. This involves the prevention of biofilm formation and preventing any corrosion and scaling phenomenon. Treatments must be optimized regularly by monitoring several physio-chemical and microbiological indicators and their performance must be verified. These indicators provide relevant information on the level of treatment control, but there is no correlation with the concentrations of Legionella which must, therefore, be measured.

Since infectious doses are not well known, maintaining a low concentration of Legionella in facilities for people at risk is the best way to minimize the risk of legionellosis.

Site monitoring

To effectively manage these facilities at risk, it is important to conduct regular monitoring to get a rapid response in case of Legionella proliferation.

This prompted Magnus to develop an innovative method in the analysis of water in cooling systems and domestic hot networks.

This method uses a gene amplification technique for detecting and counting Legionella. A DNA fragment specific to the Legionella type or Legionella pneumophila species is targeted by primers specifically designed for these bacteria and then is amplified multiple times to allow its detection and quantification.

The main advantages of this technique are, firstly, a quick response time, since the results are available within 24 hours, whereas the conventional method of culture requires ten days. Furthermore, it can analyze a fraction of the bacteria that are not usually taken into account: the viable bacteria which are not cultivable. Indeed, Legionella is a bacterium that thrives only within facilities' biofilms or within certain protozoa (Legionella having, in this case, a high infectivity) and, when present in water, is stressed by the biocides treatment. Under these conditions, it is detectable by DNA analysis, but not by culture.

Facilities which are highly affected by the risk of infection obviously include health centers and other places welcoming people at risk.

Although the counting process by culture remains the conventional method, which is based on references ​​issued by regulations and recommendations, the DNA detection method allows a regular and frequent facilities' monitoring. It makes it possible to obtain a rapid response to any deviation of Legionella's concentrations.. 

Management of legionella's risks can’t be done effectively through isolated actions or occasional massive disinfection, but must instead be based on a comprehensive program that takes into account the characteristics of each system and that combines the procedures of treatment and maintenance suitable for continuous monitoring of the installation.

Pierre Hiernaux, Ph.D. Microbiology, Management of Legionella's risks

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