Legionella pneumophila

Legionella pneumophila, the primary causative agent for Legionnaire's disease, is an aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium. L. pneumophila is a intracellular parasite that preferentially infects soil amoebae and freshwater protozoa for replication. Due to L. pneumophila’s ability to thrive in water, it can grow in water filtration systems, leading to faucets, showers, and other fixtures. Aerosolized water droplets containing L. pneumophila originating from these fixtures may be inhaled by humans. Upon entry to the human respiratory tract, L. pneumophila is able to infect and reproduce within human alveolar macrophages. This causes the onset of Legionnaires' disease, also known as legionellosis. Infected humans may display symptoms such as fever, delirium, diarrhea, and decreased liver and kidney function. L. pneumophila infections can be diagnosed by a urine antigen test. The infections caused by the bacteria can be treated with fluoroquinolones and azithromycin antibiotics.