Legionella in water distribution systems

Yuan, Lin; Vidić, Radisav D.; Stout, Janet E.; Yu, Victor L.

doi:10.1002/j.1551-8833.1998.tb08503.x

Cited by 69 publications

(57 citation statements)

References 82 publications

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“…In vitro studies using cocultures have repeatedly demonstrated the intracellular multiplication of L. pneumophila in amoebae (Acanthamoeba, Echinamoeba, Hartmannella, Naegleria, Vahlkampfia, and Dictyostelium) and in a ciliated protozoon (Tetrahymena pyriformis) (12,15,21,39). Amoebae have been observed in water systems associated with Legionnaires' disease (5, 7), and L. pneumophila can recolonize water distributing systems within a few weeks after disinfection (26,27). Batch experiments with tap water showed that L. pneumophila did not multiply in the absence of protozoa, and growth in the presence of a protozoon (Hartmannella) was confirmed by the use of cocultures (14,45).…”

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confidence: 99%

Intracellular Proliferation of Legionella pneumophila in Hartmannella vermiformis in Aquatic Biofilms Grown on Plasticized Polyvinyl Chloride

Kuiper

Wullings

Akkermans

et al. 2004

Appl Environ Microbiol

114

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The need for protozoa for the proliferation of Legionella pneumophila in aquatic habitats is still not fully understood and is even questioned by some investigators. This study shows the in vivo growth of L. pneumophila in protozoa in aquatic biofilms developing at high concentrations on plasticized polyvinyl chloride in a batch system with autoclaved tap water. The inoculum, a mixed microbial community including indigenous L. pneumophila originating from a tap water system, was added in an unfiltered as well as filtered (cellulose nitrate, 3.0-m pore size) state. Both the attached and suspended biomasses were examined for their total amounts of ATP, for culturable L. pneumophila, and for their concentrations of protozoa. L. pneumophila grew to high numbers (6.3 log CFU/cm 2 ) only in flasks with an unfiltered inoculum. Filtration obviously removed the growth-supporting factor, but it did not affect biofilm formation, as determined by measuring ATP. Cultivation, direct counting, and 18S ribosomal DNA-targeted PCR with subsequent sequencing revealed the presence of Hartmannella vermiformis in all flasks in which L. pneumophila multiplied and also when cycloheximide had been added. Fluorescent in situ hybridization clearly demonstrated the intracellular growth of L. pneumophila in trophozoites of H. vermiformis, with 25.9% ؎ 10.5% of the trophozoites containing L. pneumophila on day 10 and >90% containing L. pneumophila on day 14. Calculations confirmed that intracellular growth was most likely the only way for L. pneumophila to proliferate within the biofilm. Higher biofilm concentrations, measured as amounts of ATP, gave higher L. pneumophila concentrations, and therefore the growth of L. pneumophila within engineered water systems can be limited by controlling biofilm formation.Legionella pneumophila is widespread in natural freshwater environments, despite its fastidious nature (16). The bacterium has also frequently been observed in engineered water systems such as warm water distributing systems, cooling towers, humidifiers, and fountains (25,43,50). The multiplication of the organism in water systems poses a potential human health risk when aerosolization can occur (12).Legionellae grow in vitro only in complex media with supplements of cysteine and iron salts (11). For their multiplication in vivo, other microorganisms are required, but different species of heterotrophic bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Flavobacterium sp.) alone do not support the growth of L. pneumophila (31,45). In vitro studies using cocultures have repeatedly demonstrated the intracellular multiplication of L. pneumophila in amoebae (Acanthamoeba, Echinamoeba, Hartmannella, Naegleria, Vahlkampfia, and Dictyostelium) and in a ciliated protozoon (Tetrahymena pyriformis) (12,15,21,39). Amoebae have been observed in water systems associated with Legionnaires' disease (5, 7), and L. pneumophila can recolonize water distributing systems within a few weeks after disinfection (26,27). Batch experiments with tap wate...

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confidence: 99%

Intracellular Proliferation of Legionella pneumophila in Hartmannella vermiformis in Aquatic Biofilms Grown on Plasticized Polyvinyl Chloride

Kuiper

Wullings

Akkermans

et al. 2004

Appl Environ Microbiol

114

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“…in hospital hot water systems (8). Copper and silver ions are electrolytically generated and introduced into recirculating hot water lines.…”

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confidence: 99%

“…The first 16 hospitals in the United States that installed these systems remain operational today, and each has reported efficacious results in controlling Legionella in its water distribution system after 5 to 11 years of operation (J. E. Stout, Y. E. Lin, and V. L. Yu, Survey of hospitals using copper-silver ionization for the control of Legionella, abstract from the 5th International Conference on Legionella, p. 80, 2000). The coppersilver ionization systems have outperformed hyperchlorination, superheating and flushing, and UV light systems because of the following advantages: (i) installation and maintenance are easy; (ii) efficacy is not affected by high water temperatures (unlike with chlorine and UV light systems); (iii) residual disinfectant protection occurs throughout the system (unlike with UV light); and (iv) recolonization is delayed because coppersilver ions kill rather than suppress Legionella (unlike with chlorine) (8). Disadvantages of copper-silver ionization systems have rarely been reported.…”

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confidence: 99%

Negative Effect of High pH on Biocidal Efficacy of Copper and Silver Ions in Controlling Legionella pneumophila

Yuan

Vidic²,

Stout

et al. 2002

Appl Environ Microbiol

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Copper-silver (Cu-Ag) ionization has effectively controlled Legionella spp. in the hot water systems of numerous hospitals. However, it was ineffective at controlling Legionella in one Ohio hospital despite the confirmation of adequate total concentrations of copper and silver ions. The pH of the water at this hospital was found to be 8.5 to 9.0. The purpose of this study was to investigate the impact of pH and other water quality parameters, including alkalinity (HCO 3 ؊ ), hardness (Ca 2؉ and Mg 2؉ ), and amount of dissolved organic carbon (DOC), on the control of Legionella by Cu-Ag ionization. Initial concentrations of Legionella and copper and silver ions used in batch experiments were 3 ؋ 10 6 CFU/ml and 0.4 and 0.08 mg/liter, respectively. Changes in bicarbonate ion concentration (50, 100, and 150 mg/liter), water hardness (Ca 2؉ at 50 and 100 mg/liter; Mg 2؉ at 40 and 80 mg/liter), and level of DOC (0.5 and 2 mg/liter) had no significant impact on the efficacy of copper and silver ions in killing Legionella at a neutral pH. When the pH was elevated to 9 in these experiments, copper ions achieved only a 10-fold reduction in the number of Legionella organisms in 24 h, compared to a millionfold decrease at pH 7.0. Silver ions were able to achieve a millionfold reduction in 24 h at all ranges of water quality parameters tested. Precipitation of insoluble copper complexes was observed at a pH above 6.0. These results suggest that pH may be an important factor in the efficacy of copper-silver ionization in controlling Legionella in water systems.

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“…Currently, several methods are available for this purpose, including superheating (thermal eradication), ultraviolet light, copper-silver ionization, hyperchlorination, chloramines, ozone treatment, and chlorine dioxide. 8 Although hot water systems have long been regarded as the primary reservoirs for these organisms, there is growing evidence to suggest that contamination of potable (drinking or cold) water systems may be an even more important risk for nosocomial infections. 9,10 Thus, there is growing interest in evaluating the efficacy and safety of these methods for the treatment of both hot and potable water supplies in hospitals.…”

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confidence: 99%

A 17-Month Evaluation of a Chlorine Dioxide Water Treatment System to Control Legionella Species in a Hospital Water Supply

Srinivasan

Bova

Ross

et al. 2003

Infect. Control Hosp. Epidemiol.

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Objective:To assess the safety and efficacy of a chlorine dioxide water treatment system in controlling Legionella in a hospital water supply.Design:For 17 months following installation of the system, we performed regular water cultures throughout the building, assessed chlorine dioxide and chlorite levels, and monitored metal corrosion.Results:Sites that grew Legionella species decreased from 41% at baseline to 4% (P = .001). L. anisa was the only species recovered and it was found in samples of both hot and cold water. Levels of chlorine dioxide and chlorite were below Environmental Protection Agency (EPA) limits for these chemicals in potable water. Further, enhanced carbon filtration effectively removed the chemicals, even at chlorine dioxide levels of more than twice what was used to treat the water. After 9 months, corrosion of copper test strips exposed to the chlorine dioxide was not higher than that of control strips. During the evaluation period, there were no cases of nosocomial Legionella in the building with the system, whereas there was one case in another building.Conclusions:Our results indicate that operation of a chlorine dioxide system effectively removed Legionella species from a hospital water supply. Furthermore, we found that the system was safe, as levels of chlorine dioxide and chlorite were below EPA limits. The system did not appear to cause increased corrosion of copper pipes. Our results indicate that chlorine dioxide may hold promise as a solution to the problem of Legionella contamination of hospital water supplies.

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Legionella in water distribution systems

Cited by 69 publications

References 82 publications

Intracellular Proliferation of Legionella pneumophila in Hartmannella vermiformis in Aquatic Biofilms Grown on Plasticized Polyvinyl Chloride

Intracellular Proliferation of Legionella pneumophila in Hartmannella vermiformis in Aquatic Biofilms Grown on Plasticized Polyvinyl Chloride

Negative Effect of High pH on Biocidal Efficacy of Copper and Silver Ions in Controlling Legionella pneumophila

A 17-Month Evaluation of a Chlorine Dioxide Water Treatment System to Control Legionella Species in a Hospital Water Supply

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