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Laboratory and field applications of UV light disinfection on six species of Legionella and other bacteria in water

... Las radiaciones ultravioletas matan a las bacterias interrumpiendo la síntesis del DNA celular. La eficacia de las radiaciones ultravioletas para matar la L. pneumophila ha sido demostrada in vitro e in vivo (63)(64)(65)(66)(67)(68)(69). ...
Legionellae are bacteria that have been identified as the cause of legionellosis. Based on a rate of about 1.2 cases of legionellosis/10,000 persons/yr (Foy et al. 1979), more than 25,000 cases of this disease are estimated to occur annually within the U.S. These cases are caused primarily by one of 23 currently recognized species of the genus Legionella. Most cases of legionnaires’ disease, the pneumonia form of legionellosis, have developed in persons who were immunosuppressed or appeared to be more susceptible because of an underlying illness, heavy smoking, alcoholism, or age (i.e., more than 50 years old). In contrast, although legionnaires’ disease has developed in some healthy persons, outbreaks involving healthy persons have been limited to the milder, nonpneumonia form of the disease called Pontiac fever.
In July 1976, an outbreak of acute respiratory illness occurred during an American Legion convention in Philadelphia, Pennsylvania. Of 4,400 attendees, and some other individuals not directly associated with the convention, 221 became ill and 34 of these cases died (Fraser et al., 1977). The cause of the epidemic was unknown until later that year, when investigators at the Centers for Disease Control isolated the responsible bacterium, subsequently termed Legionella pneumophila (lung-loving) (McDade et al., 1977).
Legionella can cause two distinct diseases. The first one is Legionnaires’ disease, which is characterized by a pneumonia with a significant mortality rate. The second disease is Pontiac fever, a nonpneumonic, self‐limiting, febrile disease with a high attack rate. This review analyzes the growth, identification, survival, and pathogenicity of Legionella isolated from environmental sources including soil, mud, showers, nebulizers, potable water, water from streams, lakes, water storage tanks, evaporative condensers, cooling towers, and humidifers. The importance of algal metabolites and Flavobacterium for the growth requirements of Legionella in aquatic habitats and plumbing systems is critically evaluated. The final section of the review describes the efficacy of various methods for decontamination of environmental sources of Legionella.
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This article reviews the clinical symptoms of legionnaires' disease, describes the natural and man-made habitats of Legionella pneumophila, and evaluates various disinfection methods. Although heat rejection devices (cooling towers and evaporative condensers) have been linked to outbreaks of legionnaires' disease, recent evidence suggests that potable water distribution systems are the primary reservoirs of L. pneumophila. Inhalation of aerosols containing the organism, instillation of the organism into the lung via medical maneuvers of the respiratory tract, and aspiration of contaminated water into the lung are the most likely modes of transmission of L. pneumophila. Treatment methodologies include hyperchlorination, thermal eradication, ozonation, and ultraviolet light irradiation. Este artículo revisa los síntomas clínicos de la enfermedad de legionarios, describe las habitaciones naturales y humanas de neumofila Legionela, y evalúa varios métodos de desinfección. Aunque aparatos de rechazamiento de calor (torres refrescantes y condensadores evaporadores) han sido relacionados con brotes de la enfermedad de legionarios, evidencia corriente sugiere que los sistemas de distribución de agua potable son los depósitos primarios de neumofila L. Inhalación de aérosoles conteniendo el organismo, instalación del organismo dentro del pulmón vía maniobras médicas del sistema respiratorio, y aspiración de agua contaminada dentro del pulmón son probablamente los métodos de transmisión de neumofila L. Metodologías de tratamiento incluyen hiperclorinación, erradicación termal, ozonación, e irradiación con luz ultravioleta.
It is shown that in ultraviolet germicidal irradiation (UVGI) systems for air disinfection, where turbulence completely mixes the flow in the directions perpendicular to the net flow direction, turbulence can also act to reduce the effectiveness of the system. This occurs when the longitudinal diffusion coefficient resulting from the turbulence is large enough to reduce the effective transit time of the air through the ultraviolet irradiation zone. At the same time, depending on the radiation fluence, UV kill rate parameter, diffusion coefficient, and flow rate, the longitudinal turbulent diffusion can also increase the effectiveness of the UVGI system. The appropriate combination of parameters for ascertaining whether turbulence reduces or increases UVGI effectiveness is derived.
Regular culturing of distribution system samples is the key to successful disinfection. Legionnaires' disease arises from the presence of Legionella in water systems. Legionella can be found within biofilms throughout the entire water distribution system. Control measures such as copper‐silver ionization, superheat‐and‐flush procedures, ultraviolet light, instantaneous heating systems, and hyperchlorination have been applied with variable success. Specific approaches, advantages, disadvantages, and costs of each method are reviewed. Many approaches commonly recommended by public health authorities have not been scientifically validated. Results from routine environmental surveillance cultures for Legionella are the critical component for rational decision‐making.
Rash associated with use of whirlpools-Maine
Centers for Disease Control. 1979. Rash associated with use of whirlpools-Maine. Morbid. Mortal. Weekly Rep. 28:182-184.
Water-related disease outbreaks
Centers for Disease Control. 1982. Water-related disease outbreaks. Annual Summary 1981, issued September 1982, p. 1l-13. Centers for Disease Control, Atlanta, Ga.