What is Legionella?
Legionella are ubiquitous over the entire world found in a wide array of water systems. The bacteria are found primarily in association with unicellular protozoan and perhaps as members of biofilms. Many species are known to cause illness in humans, while others have only been isolated as environmental samples. The primary species isolated from patient material is Legionella pneumophila. The interaction of the bacteria with the host organism is the focus of numerous research programs and it serves as a model organism for facultative intracellular bacteria.
(Photo: Giemsa stain of Acanthamoeba polyphaga with L. pneumophila (dark rods) replicating within vacuoles)

