Long-term persistence of infectious Legionella with free-living amoebae in drinking water biofilms

Shaheen, Mohamed; Scott, C.D.; Ashbolt, Nicholas J.

doi:10.1016/j.ijheh.2019.04.007

Cited by 40 publications

(38 citation statements)

References 77 publications

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“…The current approach in Legionella control involves monitoring of Legionella sp. with culture-based methods and does not allow to assess true concentration of Legionella cells [43]. The data obtained in our study can help to focus on the extensive distribution, close interaction, and long-term persistence of Legionella and FLA.…”

Section: Discussionmentioning

confidence: 97%

Co-Occurrence of Free-Living Amoeba and Legionella in Drinking Water Supply Systems

et al. 2019

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Background and Objectives: Legionella is one of the most important water-related pathogens. Inside the water supply systems and the biofilms, Legionella interact with other bacteria and free-living amoeba (FLA). Several amoebas may serve as hosts for bacteria in aquatic systems. This study aimed to investigate the co-occurrence of Legionella spp. and FLA in drinking water supply systems. Materials and Methods: A total of 268 water samples were collected from apartment buildings, hotels, and public buildings. Detection of Legionella spp. was performed in accordance with ISO 11731:2017 standard. Three different polymerase chain reaction (PCR) protocols were used to identify FLA. Results: Occurrence of Legionella varied from an average of 12.5% in cold water samples with the most frequent occurrence observed in hot water, in areas receiving untreated groundwater, where 54.0% of the samples were Legionella positive. The occurrence of FLA was significantly higher. On average, 77.2% of samples contained at least one genus of FLA and, depending on the type of sample, the occurrence of FLA could reach 95%. In the samples collected during the study, Legionella was always isolated along with FLA, no samples containing Legionella in the absence of FLA were observed. Conclusions: The data obtained in our study can help to focus on the extensive distribution, close interaction, and long-term persistence of Legionella and FLA. Lack of Legionella risk management plans and control procedures may promote further spread of Legionella in water supply systems. In addition, the high incidence of Legionella-related FLA suggests that traditional monitoring methods may not be sufficient for Legionella control.

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Section: Discussionmentioning

confidence: 97%

Co-Occurrence of Free-Living Amoeba and Legionella in Drinking Water Supply Systems

et al. 2019

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“…Intracellular growth of Lp in biofilm is dependent on the concentration of host cells (Shaheen et al, 2019). The presence of host cells in the biofilm as well as the temperature being between 22.7 and 30.7°C in the pipes (Figure 3B) suggest that Legionella had ideal growth conditions (Ashbolt, 2015;Fields et al, 2002;Moffat and Tompkins, 1992;Rowbotham, 1980).…”

Section: Presence Of Legionella In the Systemmentioning

confidence: 99%

Impact of temperature on Legionella pneumophila, its protozoan host cells, and the microbial diversity of the biofilm community of a pilot cooling tower

Paniagua

Paranjape

et al. 2020

Science of The Total Environment

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Legionella pneumophila (Lp) is a waterborne bacterium known for causing Legionnaires' Disease, a severe pneumonia. Cooling towers are a major source of outbreaks, since they provide ideal conditions for Lp growth and produce aerosols. In such systems, Lp typically grow inside protozoan hosts. Several abiotic factors such as water temperature, pipe material and disinfection regime affect the colonization of cooling towers by Lp. The local physical and biological factors promoting the growth of Lp in water systems and its spatial distribution are not well understood.Therefore, we built a lab-scale cooling tower to study the dynamics of Lp colonization in relationship to the resident microbiota and spatial distribution. The pilot was filled with water from an operating cooling tower harboring low levels of Lp. It was seeded with Vermamoeba vermiformis, a natural host of Lp, and then inoculated with Lp. After 92 days of operation, the pilot was disassembled, the water was collected, and biofilm was extracted from the pipes. The microbiome was studied using 16S rRNA and 18S rRNA genes amplicon sequencing. The communities of the water and of the biofilm were highly dissimilar. The relative abundance of Legionella in water samples reached up to 11% whereas abundance in the biofilm was extremely low (≤0.5 %). In contrast, the host cells were mainly present in the biofilm. This suggest that Lp grows in host cells associated with biofilm and is then released back into the water following host cell lysis. In addition, water temperature shaped the bacterial and eukaryotic community of the biofilm, indicating that different parts of the systems may have different effects on Legionella growth.

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“…Firstly, the species and abundance of the prey community is an important factor for growth of the protozoan host population. Grazing is usually a selective process that depends on the prey species, prey morphology, prey size and physiological state of the prey and of the predator [34][35][36]. As a result, factors affecting the prey community will have consequences on the Legionella host community, and therefore, indirectly on the Legionella community.…”

Section: Introductionmentioning

confidence: 99%

Unravelling the importance of the eukaryotic and bacterial communities and their relationship with Legionella spp. ecology in cooling towers: a complex network

et al. 2020

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Background Cooling towers are a major source of large community-associated outbreaks of Legionnaires’ disease, a severe pneumonia. This disease is contracted when inhaling aerosols that are contaminated with bacteria from the genus Legionella, most importantly Legionella pneumophila. How cooling towers support the growth of this bacterium is still not well understood. As Legionella species are intracellular parasites of protozoa, it is assumed that protozoan community in cooling towers play an important role in Legionella ecology and outbreaks. However, the exact mechanism of how the eukaryotic community contributes to Legionella ecology is still unclear. Therefore, we used 18S rRNA gene amplicon sequencing to characterize the eukaryotic communities of 18 different cooling towers. The data from the eukaryotic community was then analysed with the bacterial community of the same towers in order to understand how each community could affect Legionella spp. ecology in cooling towers. Results We identified several microbial groups in the cooling tower ecosystem associated with Legionella spp. that suggest the presence of a microbial loop in these systems. Dissolved organic carbon was shown to be a major factor in shaping the eukaryotic community and may be an important factor for Legionella ecology. Network analysis, based on co-occurrence, revealed that Legionella was correlated with a number of different organisms. Out of these, the bacterial genus Brevundimonas and the ciliate class Oligohymenophorea were shown, through in vitro experiments, to stimulate the growth of L. pneumophila through direct and indirect mechanisms. Conclusion Our results suggest that Legionella ecology depends on the host community, including ciliates and on several groups of organisms that contribute to its survival and growth in the cooling tower ecosystem. These findings further support the idea that some cooling tower microbiomes may promote the survival and growth of Legionella better than others.

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Long-term persistence of infectious Legionella with free-living amoebae in drinking water biofilms

Cited by 40 publications

References 77 publications

Co-Occurrence of Free-Living Amoeba and Legionella in Drinking Water Supply Systems

Co-Occurrence of Free-Living Amoeba and Legionella in Drinking Water Supply Systems

Impact of temperature on Legionella pneumophila, its protozoan host cells, and the microbial diversity of the biofilm community of a pilot cooling tower

Unravelling the importance of the eukaryotic and bacterial communities and their relationship with Legionella spp. ecology in cooling towers: a complex network

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