Pathogenesis of Legionella pneumophila in Humans

Legionella pneumophila is a Gram‐negative rod‐shaped bacterium belonging to the gamma‐subgroup of proteobacteria. L. pneumophila is the most common infectious agent of Legionnaires’ disease worldwide. This chapter discusses the epidemiology of the disease, genome organization of L. pneumophila, evolution of L. pneumophila, and its pathogenesis. It also covers clinical features, diagnosis, treatment, and prevention and control of Legionnaires’ disease. L. pneumophila possesses a remarkable ability to manipulate various host cell processes to form a protective, membrane‐bound vacuole that supports intracellular replication known as the Legionella‐containing vacuole (LCV). L. pneumophila alternates between two growth states during infection, namely a non‐motile, thin‐walled replicative form and a motile, thick‐walled infectious form. After numerous rounds of replication, nutrients become limited, triggering the switch to the infectious form. The major cause of death in patients with Legionnaires’ disease is respiratory failure.