Prevent stagnation, for example, by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, as when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation. Prevent the buildup of biofilm, for example, by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system. Periodically disinfect the system, by high heat or a chemical biocide, and use chlorination where appropriate. Treatment of water with copper-silver ionization or ultraviolet light may also be effective. System design (or renovation) can reduce the production of aerosols and reduce human exposure to them, by directing them well away from building air intakes.An effective water safety plan also covers such matters as training, record-keeping, communication among staff, contingency plans, and management responsibilities. The format and content of the plan may be prescribed by public health laws or regulations. To inform the water safety plan, the undertaking of a site specific legionella risk assessment is often recommended in the first instance. The legionella risk assessment identifies the hazards, the level of risk they pose and provides recommendations of control measures to put place within the overarching water safety plan. Treatment
Effective antibiotics include most macrolides, tetracyclines, ketolides, and quinolones. Legionella spp. multiply within the cell, so any effective treatment must have excellent intracellular penetration.
Sources where temperatures allow the bacteria to thrive include hot water tanks, cooling towers, and evaporative condensers of large air conditioning systems, such as those commonly found in hotels and large office buildings. Though the first known outbreak was in Philadelphia, cases of legionellosis have occurred throughout the world. Reservoirs
L. pneumophila thrives in aquatic systems, where it is established within amoebae in a symbiotic relationship. Legionella bacteria survive in water as intracellular parasites of water-dwelling protozoa, such as amoebae. Amoebae are often part of biofilms, and once Legionella and infected amoebae are protected within a biofilm, they are particularly difficult to destroy.In the built environment, central air conditioning systems in office buildings, hotels, and hospitals are sources of contaminated water. Other places the bacteria can dwell include cooling towers used in industrial cooling systems, evaporative coolers, nebulizers, humidifiers, whirlpool spas, hot water systems, showers, windshield washers, fountains, room-air humidifiers, ice-making machines, and misting systems typically found in grocery-store produce sections.The bacteria may also be transmitted from contaminated aerosols generated in hot tubs if the disinfection and maintenance programs are not followed rigorously. Freshwater ponds, creeks, and ornamental fountains are potential sources of Legionella. The disease is particularly associated with hotels, fountains, cruise ships, and hospitals with complex potable water systems and cooling systems. Respiratory-care devices such as humidifiers and nebulizers used with contaminated tap water may contain Legionella species, so using sterile water is very important. Other sources include exposure to potting mix and compost. Mechanism
Legionella spp.