Legionella pneumophila

Legionella pneumophila is a thin, aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium of the genus Legionella. It is the primary human pathogenic bacterium in this group and is the causative agent of Legionnaires' disease, also known as legionellosis.

Characteristics

Legionella pneumophila, like all Legionella species, is found in fresh water environments, such as lakes and streams. It can survive in a wide range of temperatures, but prefers temperatures between 25 and 45 degrees Celsius, with an optimum around 35 degrees Celsius. This makes it an ideal inhabitant of hot water systems, such as those found in large buildings, hotels, and hospitals.

Pathogenesis

Legionella pneumophila is a facultative intracellular parasite that can invade and replicate inside amoebae in the environment. This provides a training ground for invasion and replication in alveolar macrophages in the lung when inhaled. The bacteria use a secretion system to inject effector proteins into the host. These effectors modulate host cell functions to provide a replicative niche for the bacteria.

Diagnosis and Treatment

Diagnosis of Legionella pneumophila infection can be challenging, as it requires specific tests not commonly performed on patients with pneumonia. The most commonly used diagnostic method is the urinary antigen test, which detects the presence of Legionella antigen in the urine. Treatment typically involves antibiotics such as macrolides or quinolones.

Prevention

Prevention of Legionella pneumophila infection involves regular maintenance and disinfection of water systems, particularly in settings where the bacteria are likely to proliferate, such as hospitals and hotels. This can include heat treatment, chlorination, or the use of biocides.

See Also

• Legionnaires' disease
• Legionella
• Macrolides
• Quinolones