Occurrence of legionellae in hot water distribution systems of Finnish apartment buildings

The occurrence of legionellae in the hot water distribution systems of 67 buildings located in different parts of Finland was studied. Most of the buildings were apartment buildings. They had different hot water temperatures, and some received their cold potable water from surface water plants and some from ground water plants. Hot water samples were taken from taps, showers, and water mains just before and after the heat exchanger. Legionella pneumophila was isolated from 30% of the distribution systems. In the legionella-positive samples the legionella concentration varied from < 50 to 3.2 × 105 colony-forming units (cfu)/L (mean 2.7 × 103 cfu/L). The highest concentration of legionellae was found in the shower water. Legionellae appeared more often and with higher concentrations in hot water systems using cold water processed in surface water plants than in hot water systems associated with ground water plants. A high organic matter content in surface waters might favor the occurrence of legionellae and also the growth of other heterotrophic microbes. Mean water temperature just after heating was slightly higher in the legionella-negative systems than in the legionella-positive systems (53.5 vs. 51.5 °C).Key words: Legionella, organic carbon, hot water distribution system, water temperature.

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Legionella pneumophila’s Tsp is important for surviving thermal stress in water and inside amoeba

10.1101/2020.12.08.417196 ◽

2020 ◽

Author(s):

Joseph Saoud ◽

Thangadurai Mani ◽

Sébastien P. Faucher

Keyword(s):

Heat Treatment ◽

Thermal Stress ◽

Heat Shock ◽

Legionella Pneumophila ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Water Systems ◽

Exponential Phase ◽

Hot Water

ABSTRACTLegionella pneumophila (Lp) is an inhabitant of natural and man-made water systems where it replicates within amoebae and ciliates and survives within biofilms. When Lp-contaminated aerosols are breathed in, Lp will enter the lungs and infect human alveolar macrophages, causing a severe pneumonia known as Legionnaires Disease. Lp is often found in hot water distribution systems (HWDS), which are linked to nosocomial outbreaks. Heat treatment is used to disinfect HWDS and reduce the concentration of Lp. However, Lp is often able to recolonize these water systems, indicating an efficient heat-shock response. Tail-specific proteases (Tsp) are typically periplasmic proteases implicated in degrading aberrant proteins in the periplasm and important for surviving thermal stress. In this paper, we show that Tsp, encoded by the lpg0499 gene in Lp Philadelphia-1, is important for surviving thermal stress in water and for optimal infection of amoeba when a shift in temperature occurs during intracellular growth. Tsp is expressed in the post-exponential phase but repressed in the exponential phase. The cis-encoded small regulatory RNA Lpr17 shows opposite expression, suggesting that it represses translation of tsp. In addition, tsp is regulated by CpxR, a major regulator in Lp, in a Lpr17-independent manner. Deletion of CpxR also reduced the ability of Lp to survive heat shock. In conclusion, this study shows that Tsp is an important factor for the survival and growth of Lp in water systems.IMPORTANCELegionella pneumophila (Lp) is a major cause of nosocomial and community-acquired pneumonia. Lp is found in water systems including hot water distribution systems. Heat treatment is a method of disinfection often used to limit Lp’s presence in such systems; however, the benefit is usually short term as Lp is able to quickly recolonize these systems. Presumably, Lp respond efficiently to thermal stress, but so far not much is known about the genes involved. In this paper, we show that the Tail-specific protease (Tsp) and the two-component system CpxRA are required for resistance to thermal stress, when Lp is free in water and when it is inside host cells. Our study identifies critical systems for the survival of Lp in its natural environment under thermal stress.

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The Tail-Specific Protease Is Important for Legionella pneumophila To Survive Thermal Stress in Water and inside Amoebae

Applied and Environmental Microbiology ◽

10.1128/aem.02975-20 ◽

2021 ◽

Vol 87 (9) ◽

Author(s):

Joseph Saoud ◽

Thangadurai Mani ◽

Sébastien P. Faucher

Keyword(s):

Heat Treatment ◽

Thermal Stress ◽

Heat Shock ◽

Legionella Pneumophila ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Water Systems ◽

Hot Water ◽

Host Cells

ABSTRACT Legionella pneumophila (Lp) is an inhabitant of natural and human-made water systems, where it replicates within amoebae and ciliates and survives within biofilms. When Lp-contaminated aerosols are breathed in, Lp can enter the lungs and may infect human alveolar macrophages, causing severe pneumonia known as Legionnaires’ disease. Lp is often found in hot water distribution systems (HWDS), which are linked to nosocomial outbreaks. Heat treatment is used to disinfect HWDS and reduce the concentration of Lp. However, Lp is often able to recolonize these water systems, indicating an efficient heat shock response. Tail-specific proteases (Tsp) are typically periplasmic proteases implicated in degrading aberrant proteins in the periplasm and important for surviving thermal stress. In Lp Philadelphia-1, Tsp is encoded by the lpg0499 gene. In this paper, we show that Tsp is important for surviving thermal stress in water and for optimal infection of amoeba when a shift in temperature occurs during intracellular growth. We also demonstrate that Tsp is expressed in the postexponential phase but repressed in the exponential phase and that the cis-encoded small regulatory RNA Lpr17 shows the opposite expression, suggesting that it represses translation of tsp. In addition, our results show that tsp is regulated by CpxR, a major regulator in Lp, in an Lpr17-independent manner. Deletion of CpxR also reduced the ability of Lp to survive heat shock. In conclusion, our study shows that Tsp is likely an important factor for the survival and growth of Lp in water systems. IMPORTANCE Lp is a major cause of nosocomial and community-acquired pneumonia. Lp is found in water systems, including hot water distribution systems. Heat treatment is a method of disinfection often used to limit the presence of Lp in such systems; however, the benefit is usually short term, as Lp is able to quickly recolonize these systems. Presumably, Lp responds efficiently to thermal stress, but so far, not much is known about the genes involved. In this paper, we show that the Tsp and the two-component system CpxRA are required for resistance to thermal stress when Lp is free in water and when it is inside host cells. Our study identifies critical systems for the survival of Lp in its natural environment under thermal stress.

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MUWS (Microbiology in Urban Water Systems) – an interdisciplinary approach to study microbial communities in urban water systems

Drinking Water Engineering and Science ◽

10.5194/dwes-3-91-2010 ◽

2010 ◽

Vol 3 (2) ◽

pp. 91-99 ◽

Cited By ~ 2

Author(s):

P. Deines ◽

R. Sekar ◽

H. S. Jensen ◽

S. Tait ◽

J. B. Boxall ◽

...

Keyword(s):

Microbial Ecology ◽

Distribution Systems ◽

Water Distribution ◽

Potable Water ◽

Water Distribution Systems ◽

Water Systems ◽

Urban Water ◽

Infrastructure Systems ◽

Urban Water Systems ◽

Sewer Networks

Abstract. Microbiology in Urban Water Systems (MUWS) is an integrated project, which aims to characterize the microorganisms found in both potable water distribution systems and sewer networks. These large infrastructure systems have a major impact on our quality of life, and despite the importance of these systems as major components of the water cycle, little is known about their microbial ecology. Potable water distribution systems and sewer networks are both large, highly interconnected, dynamic, subject to time and varying inputs and demands, and difficult to control. Their performance also faces increasing loading due to increasing urbanization and longer-term environmental changes. Therefore, understanding the link between microbial ecology and any potential impacts on short or long-term engineering performance within urban water infrastructure systems is important. By combining the strengths and research expertise of civil-, biochemical engineers and molecular microbial ecologists, we ultimately aim to link microbial community abundance, diversity and function to physical and engineering variables so that novel insights into the performance and management of both water distribution systems and sewer networks can be explored. By presenting the details and principals behind the molecular microbiological techniques that we use, this paper demonstrates the potential of an integrated approach to better understand how urban water system function, and so meet future challenges.

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How Molecular Typing Can Support Legionella Environmental Surveillance in Hot Water Distribution Systems: A Hospital Experience

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17228662 ◽

2020 ◽

Vol 17 (22) ◽

pp. 8662

Author(s):

Luna Girolamini ◽

Silvano Salaris ◽

Jessica Lizzadro ◽

Marta Mazzotta ◽

Maria Rosaria Pascale ◽

...

Keyword(s):

Legionella Pneumophila ◽

Molecular Typing ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Gene Sequencing ◽

Culture Technique ◽

Hot Water ◽

Environmental Surveillance ◽

Risk Map

In this study, we aimed to associate the molecular typing of Legionella isolates with a culture technique during routine Legionella hospital environmental surveillance in hot water distribution systems (HWDSs) to develop a risk map able to be used to prevent nosocomial infections and formulate appropriate preventive measures. Hot water samples were cultured according to ISO 11731:2017. The isolates were serotyped using an agglutination test and genotyped by sequence-based typing (SBT) for Legionella pneumophila or macrophage infectivity potentiator (mip) gene sequencing for non-pneumophila Legionella species. The isolates’ relationship was phylogenetically analyzed. The Legionella distribution and level of contamination were studied in relation to temperature and disinfectant residues. The culture technique detected 62.21% of Legionella positive samples, characterized by L. pneumophila serogroup 1, Legionella non-pneumophila, or both simultaneously. The SBT assigned two sequence types (STs): ST1, the most prevalent in Italy, and ST104, which had never been isolated before. The mip gene sequencing detected L. anisa and L. rubrilucens. The phylogenetic analysis showed distinct clusters for each species. The distribution of Legionella isolates showed significant differences between buildings, with a negative correlation between the measured level of contamination, disinfectant, and temperature. The Legionella molecular approach introduced in HWDSs environmental surveillance permits (i) a risk map to be outlined that can help formulate appropriate disinfection strategies and (ii) rapid epidemiological investigations to quickly identify the source of Legionella infections.

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Fungi from Potable Water: Interaction with Chlorine and Engineering Effects

Water Science & Technology ◽

10.2166/wst.1988.0278 ◽

1988 ◽

Vol 20 (11-12) ◽

pp. 153-159 ◽

Cited By ~ 3

Author(s):

William D. Rosenzweig ◽

Wesley O. Pipes

Keyword(s):

Water Samples ◽

Distribution Systems ◽

Water Distribution ◽

Potable Water ◽

Fungal Spores ◽

Water Distribution Systems ◽

Water Systems ◽

Storage Tanks ◽

Water Interaction ◽

Low Concentrations

In recent years various types of imperfect fungi have been isolated from water systems. Fungal spores and mycelia can be inactivated by low concentrations of chlorine in the laboratory but survive in some habitats in water distribution systems. This report describes a field study which provides evidence that some types of fungi are able to grow in water distribution systems. Replicate samples from private residences were used to demonstrate that fungal densities are sometimes much greater than the levels which could be explained by adventitious spores. The microbiological content of water samples from fire hydrants was often significantly different from that of water samples from nearby private residences. The treated water input to distribution systems was found to be significantly lower in fungus content than water from private residences. Elevated storage tanks open to the atmosphere appear to be significant sources of fungal input to some systems.

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Memphis Light, Gas and Water Division Experience With Aging of Electric, Gas, and Water Systems

Applied Mechanics Reviews ◽

10.1115/1.3120333 ◽

1993 ◽

Vol 46 (5) ◽

pp. 183-186

Author(s):

Charles Pickel

Keyword(s):

United States ◽

Customer Satisfaction ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

The United States ◽

Water Systems ◽

Recent Survey ◽

Effective Manner ◽

Long Life

Electric, gas and water distribution systems can have an extremely long life when properly designed, installed and maintained. MLGW is proof positive that aging distribution systems can be managed in an effective manner. Customer satisfaction is a high priority with Division management. According to a recent survey, Memphians enjoy the lowest average monthly utility bills among the 25 largest cities in the United States.

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Occurrence of heterotrophic bacteria and fungi in cold and hot water distribution systems using water of different quality

Canadian Journal of Microbiology ◽

10.1139/m95-152 ◽

1995 ◽

Vol 41 (12) ◽

pp. 1088-1094 ◽

Cited By ~ 19

Author(s):

Outi M. Zacheus ◽

Pertti J. Martikainen

Keyword(s):

Surface Water ◽

Water Samples ◽

Distribution Systems ◽

Heterotrophic Bacteria ◽

Cold Water ◽

Hot Water ◽

Thermophilic Fungi ◽

Cell Counts ◽

Bacteria And Fungi ◽

Water Plants

The microbiological quality of cold and hot water samples of 67 Finnish buildings was studied. Most of the buildings were apartment buildings receiving their cold water from municipal groundwater or surface water plants. Disinfection with chlorine was applied in all the surface water plants and 33% of the groundwater plants. Water samples in buildings were taken from incoming cold water, from the hot water main just before and after the heat exchanger, and from a tap or shower in an apartment. The viable counts of mesophilic bacteria and fungi and total cell counts were higher in cold than in hot water samples. In hot water, the microbial counts were higher in samples from taps and showers than from the mains. In taps and showers, the decrease in hot water temperature probably increased the microbial numbers. Thermophilic bacteria appeared with high numbers in all the hot water samples, but thermophilic fungi were found in only one sample. Bacterial biomass and mean cell volume were greater in processed surface water than in processed groundwater samples. Disinfection with chlorine reduced the viable plate counts, although the chlorine concentration was extremely low in the water samples studied.Key words: heterotrophic bacteria, fungi, distribution system, groundwater, surface water.

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MUWS (Microbiology in Urban Water Systems) – an interdisciplinary approach to study microbial communities in urban water systems

Drinking Water Engineering and Science Discussions ◽

10.5194/dwesd-3-43-2010 ◽

2010 ◽

Vol 3 (1) ◽

pp. 43-64

Author(s):

P. Deines ◽

R. Sekar ◽

H. S. Jensen ◽

S. Tait ◽

J. B. Boxall ◽

...

Keyword(s):

Microbial Ecology ◽

Distribution Systems ◽

Water Distribution ◽

Potable Water ◽

Water Distribution Systems ◽

Water Systems ◽

Urban Water ◽

Microbiological Methods ◽

Urban Water Systems ◽

Sewer Networks

Abstract. Microbiology in Urban Water Systems (MUWS) is an integrated project, which aims to characterize the microorganisms found in both potable water distribution systems and sewer networks. These large infrastructure systems have a major impact on our quality of life, and despite the importance of these systems as major components of the water cycle, little is known about their microbial ecology. Potable water distribution systems are large, highly interconnected and dynamic, and difficult to control. Sewer systems are also large and subject to time varying inputs and demands. Their performance also faces increasing loading due to increasing urbanization and longer-term environmental changes. Therefore, understanding the link between microbial ecology and any potential impacts on short or long-term engineering performance is important. By combining the strengths and research expertise of civil-, biochemical engineers and molecular microbial ecologists, we aim to link the abundance and diversity of microorganisms to physical and engineering variables so that novel insights into the ecology of microorganisms within both water distribution systems and sewer networks can be explored. By presenting the details of this multidisciplinary approach, and the principals behind the molecular microbiological methods and techniques that we use, this paper will demonstrate the potential of an integrated approach to better understand urban water system function and so meet future challenges.

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