Les légionelles

Legionella, causative agents of community and nosocomial pneumonia including Legionnaire's disease find their origin from many natural aquatic environments. These pathogens have a high phenotypic and genotypic diversity and are able to colonize different artificial systems such as the hot sanitary water systems and cooling tower water systems which are well know to be the main sources of legionellosis. In France but also in Europe, the risk of exposure to Legionella is under preventive actions especially for facilities receiving significant public. This monitoring includes the periodic inspection of facilities for Legionella presence and quantification and the development of epidemiological tools to help to identify strains involved in outbreaks and environmental sources of infections. However, because of a strong interaction between the pathogen and its environment, it now seems essential to better understand the ecology of this pathogen in natural environments, including those that supply artificial systems to help for a better understanding of the risk factors for growth of Legionella in artificial systems. This review aims to inform the reader on the knowledge available on the ecology of these pathogenic bacteria.