What Is Legionella Pneumophila?

In taxonomy, Legionella pneumophila belongs to the Legionellaceae family. In addition, Legionella pneumophila belongs to the Legionellales order, the Gammaproteobacteria class, the Proteobacteria phylum, and finally the bacteria domain.1
Legionella pneumophila is a Gram-negative, rod shaped, nonsporing, aerobic, facultative bacillus bacterium that is naturally found in fresh water sources that have high algal and iron contents. Legionella pneumophila is mainly aquatic however; it has an aerobic metabolism so that it can survive for short periods of time outside of the water.2 In its natural environment, this non-capsulated intracellular parasite, infect free-living protozoa and form an endosymbiotic relationship with amoebas.3 When not inhabiting
Since home and car air conditioning systems do not use water to cool, then they do not aerosolize water and are therefore not at risk for the potential growth of Legionella pneumophila.5
The primary host of Legionella pneumophila consists of human macrophages and amoeba. The bacterium begins infection of the host by being phagocytosed by macrophages. Legionella pneumophila go through two distinctive phases in its life cycle: a replicative phase followed by an infectious phase. The replicative phase involves a non-motile bacterium, with a minimal or absent toxicity. Once inside the macrophage, before it can begin its replicative phase, Legionella pneumophila forms a membrane bound vacuole that protects the bacterium. This structural change creates a physical barrier