Microbiological monitoring of water for control of Legionella

Legionellosis is a collection of infections that are caused by Legionella pneumophila and related Legionella bacteria. The severity of legionellosis varies from mild febrile illness (Pontiac fever) to a potentially fatal form of pneumonia (Legionnaires’ disease) that can affect anyone, but principally affects those who are susceptible due to age, illness, immunosuppression or other risk factors, such as smoking. Legionella spp. are heterotrophic bacteria found in a wide range of water environments and proliferate at temperatures between 25°C and 45°C. These bacteria are members of the natural flora of many freshwater environments, such as rivers, streams and impoundments, where they occur in relatively low numbers. Bacteria of the genus Legionella are ubiquitous, they can proliferate in certain human-made water environments, such as water cooling devices associated with air conditioning systems, hot water, spas, distribution systems, on the inside surfaces of shower heads especially in warm waters. Legionellae can be ingested by certain amoebae which play an important role in their persistence in water environments. Devices that support multiplication of Legionella have been associated with outbreaks of Legionnaires’disease. Nosocomial cases usually make up a small proportion of reported cases of legionellosis. However, the proportion of cases that are fatal tends to be much higher with nosocomial infections than with community-acquired infections. Health-care facilities may include environments that support the proliferation and dissemination of Legionella and must be monitored. In Portugal only exists legislation for air conditioning systems and thermal waters. It is important to be aware of the need to develop specific rules for the detection of Legionella in water intended for human consumption in order to act more for the prevention of the disease than to act only in the monitoring of an outbreak. In recent years there has been an increasing incidence of disease caused by this bacterium, atypical pneumonia, and a large variety of water systems are different sources of contamination