Legionellae are gram-negative bacteria found in soil and water environments, where they parasitize and proliferate within free-living protozoa. Legionellae are common contaminants of artificial water systems, including air- conditioning systems, cooling towers, and jacuzzis, where conditions may be optimal for growth and proliferation. The incidence rate of Legionnaires’ disease is high in both developed and developing countries and the Legionella pneumophila species is responsible for approximately 90% of the clinical cases.