LEGIONNAIRES' DISEASE is a lung infection (pneumonia) caused by a bacterium named Legionella pneumophila.
Legionella organisms are readily found in natural aquatic bodies. The organisms can survive in a wide range of conditions, including temperatures of 0-63° C, pH of 5.0 to 8.5, and dissolved oxygen concentrations of 0.2 to 15 ppm in water. Temperature is a critical determinant for Legionella proliferation. Legionella and other microorganisms become attached to surfaces in an aquatic environment, forming a biofilm. Legionella has been shown to attach to and colonize various materials found in water systems, including plastics, rubber, and wood. Organic sediments, scale, and inorganic precipitates provide Legionella with a surface for attachment and a protective barrier. Interestingly, the growth of other environmental organisms is stimulated by organic sediment, which in turn leads to the formation of by-products that stimulate the growth of Legionella.