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Legionella is a genus of gram-negative bacteria that can be seen using a silver stain or grown in a special media that contains cysteine, an amino acid.It is known to cause legionellosis [3] (all illnesses caused by Legionella) including a pneumonia-type illness called Legionnaires' disease and a mild flu-like illness called Pontiac fever. [3]
Legionella pneumophila, the primary causative agent for Legionnaire's disease, is an aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium. [1] [2] L. pneumophila is a intracellular parasite that preferentially infects soil amoebae and freshwater protozoa for replication.
Legionella spp. enter the lungs either by aspiration of contaminated water or inhalation of aerosolized contaminated water or soil. In the lung, the bacteria are consumed by macrophages , a type of white blood cell , inside of which the Legionella bacteria multiply, causing the death of the macrophage.
Almost all natural water sources contain Legionella and their presence should not be taken as an indication of a problem. The tabled figures are for total aerobic plate count, cfu/ml at 30 °C (minimum 48 hours incubation) with colony count determined by the pour plate method according to ISO 6222(21) or spread plate method on yeast extract agar.
Most isolates of Legionella have been from air-conditioning cooling towers and potable-water distribution systems, but they can also be found in other thermally polluted water sources such as air conditioners, spa equipment, fountains, humidifiers, or showers. [15] They can also be collected on the surfaces of lakes, mud, and streams.
Legionella is considered to be pathogenic in humans and is one of the leading outbreaks found in constructed water systems. Because the biofilms are the source, countless outbreaks that originated from water systems and the ability of a species to form biofilms both can contribute to L. clemonensis’s pathogenicity. [7]
Legionella pneumophila is the most common cause, but sometimes other species of Legionella bacteria also cause Legionnaires' disease. [ 15 ] [ 16 ] The terms "Philadelphia fever" and "Legion fever" appear to have been used at the time of the outbreak and for shortly thereafter, [ 17 ] although at least one 2008 source which covers disease in a ...
Another isolate, SC-65-C3, was found in a potable water stern on the island of St. Croix in the Virgin Islands. [1] Legionella species are mostly found in freshwater environments. [6] However, various strains of Legionella can congregate in water filtration systems, air conditioning units, humidifiers, and equipment used to combat respiratory ...