Legionellae in engineered systems and use of quantitative microbial risk assessment to predict exposure

While it is well-established that Legionella are able to colonize engineered water systems, the number of interacting factors contributing to their occurrence, proliferation, and persistence are unclear. This review summarizes current methods used to detect and quantify legionellae as well as the current knowledge of engineered water system characteristics that both favour and promote legionellae growth. Furthermore, the use of quantitative microbial risk assessment (QMRA) models to predict potentially critical human exposures to legionellae are also discussed. Understanding the conditions favouring Legionella occurrence in engineered systems and their overall ecology (growth in these systems/biofilms, biotic interactions and release) will aid in developing new treatment technologies and/or systems that minimize or eliminate human exposure to potentially pathogenic legionellae.