Role of biofilms in the survival of Legionella pneumophila to sodium chloride treatment

Background and Objectives: Legionnaires’ disease continues to be a public health concern. Colonized water distribution systems are often implicated in Legionella transmission, despite the use of various disinfection strategies, the bacterium is capable to persist and survive in water systems. The aim of this study was to investigate the persistence of Legionella pneumophila to sodium chloride over time at different temperatures and analysing the role of biofilms in the survival of this bacteria. Materials and Methods: L. pneumophila serogroup 1 and L. pneumophila serogroup 2-15 were used to study the effect of sodium chloride on planktonic and sessile cells. The tested concentrations were: 0.5%, 1%, 2%, 3%, 4%, 6% and 8% (W/V) NaCl. Biofilms were grown on 24-well microplates. Results: At 20°C, L. pneumophila planktonic cells were able to survive in sodium chloride concentrations up to 2%. How- ever, at 37°C, a sodium chloride concentration over 1.5%, reduced systematically the numbers of bacterial cells. Biofilms were grown for 20 days in the absence and presence of sodium chloride. The results show that bacterial strains were able to survive and regrow after the sodium chloride shock (2-3%). Moreover, it seems that this effect is less expressed with the age of the biofilm; old biofilms were more persistent than the young ones. Conclusion: Results from this study demonstrate that the sodium chloride disinfection strategy was effective on Legionella pneumophila planktonic cells but not on biofilms, which demonstrate the role of biofilms in the persistence and recoloniza- tion of L. pneumophila in water distribution systems.

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The role of biofilm in the development and dissemination of ubiquitous pathogens in drinking water distribution systems: an overview of surveillance, outbreaks, and prevention

World Journal of Microbiology and Biotechnology ◽

10.1007/s11274-021-03008-3 ◽

2021 ◽

Vol 37 (2) ◽

Author(s):

Bahaa A. Hemdan ◽

Gamila E. El-Taweel ◽

Pranab Goswami ◽

Deepak Pant ◽

Surajbhan Sevda

Keyword(s):

Drinking Water ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Drinking Water Distribution Systems ◽

Drinking Water Distribution

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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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Legionella pneumophila and Protozoan Hosts: Implications for the Control of Hospital and Potable Water Systems

Pathogens ◽

10.3390/pathogens9040286 ◽

2020 ◽

Vol 9 (4) ◽

pp. 286 ◽

Cited By ~ 2

Author(s):

Muhammad Atif Nisar ◽

Kirstin E. Ross ◽

Melissa H. Brown ◽

Richard Bentham ◽

Harriet Whiley

Keyword(s):

Legionella Pneumophila ◽

Distribution Systems ◽

Water Distribution ◽

Potable Water ◽

Water Systems ◽

Water Disinfection ◽

Health Concern ◽

Waterborne Pathogen ◽

Microbial Biofilms ◽

Pontiac Fever

Legionella pneumophila is an opportunistic waterborne pathogen of public health concern. It is the causative agent of Legionnaires’ disease (LD) and Pontiac fever and is ubiquitous in manufactured water systems, where protozoan hosts and complex microbial communities provide protection from disinfection procedures. This review collates the literature describing interactions between L. pneumophila and protozoan hosts in hospital and municipal potable water distribution systems. The effectiveness of currently available water disinfection protocols to control L. pneumophila and its protozoan hosts is explored. The studies identified in this systematic literature review demonstrated the failure of common disinfection procedures to achieve long term elimination of L. pneumophila and protozoan hosts from potable water. It has been demonstrated that protozoan hosts facilitate the intracellular replication and packaging of viable L. pneumophila in infectious vesicles; whereas, cyst-forming protozoans provide protection from prolonged environmental stress. Disinfection procedures and protozoan hosts also facilitate biogenesis of viable but non-culturable (VBNC) L. pneumophila which have been shown to be highly resistant to many water disinfection protocols. In conclusion, a better understanding of L. pneumophila-protozoan interactions and the structure of complex microbial biofilms is required for the improved management of L. pneumophila and the prevention of LD.

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Multiple disinfection processes of Legionella pneumophila positive in hotels’ water distribution systems in Jordan

10.5004/dwt.2019.24411 ◽

2019 ◽

Vol 163 ◽

pp. 7-16

Author(s):

Motasem N. Saidan ◽

Ahlam I. Abdalla ◽

Nivin Al Alami ◽

Hanan Al-Naimat

Keyword(s):

Legionella Pneumophila ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems

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Environmental Surveillance of Legionella spp. in an Italian University Hospital Results of 10 Years of Analysis

Water ◽

10.3390/w13162304 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2304

Author(s):

Giovanna Deiana ◽

Antonella Arghittu ◽

Marco Dettori ◽

Maria Dolores Masia ◽

Maria Grazia Deriu ◽

...

Keyword(s):

Legionella Pneumophila ◽

Distribution Systems ◽

Water Distribution ◽

Linear Trend ◽

Water Distribution Systems ◽

University Hospital ◽

Environmental Surveillance ◽

National Guidelines ◽

Increased Risk ◽

Definitive Method

The occurrence of Legionella spp. in the water distribution systems of large hospitals and other healthcare facilities is considered particularly dangerous, due to the critical nature of the hospitalized patients. The aim of this study is to present a pluri-annual environmental surveillance in a large university hospital assessing the prevalence of Legionella spp. and underlining its variability over the years. The samples of water were collected in accordance with the Italian National Guidelines and the sampling sites considered in this study were selected favoring wards with very high-risk patients and with patients at increased risk. The laboratory analyzed a total of 305 water samples deriving from 24 different sampling points. Legionella spp. were detected in 39.4% of samples, the majority of which were contaminated by Legionella pneumophila serogroups 2–14 (68.7%). Statistically significant differences were found among different seasons with a linear trend in positive proportion from summer to spring. Several experimental interventions to prevent and reduce Legionella colonization were attempted, but there is no a definitive method for the complete eradication of this microorganism. The permanent monitoring of hospital water distribution systems is fundamental to preventing the potential risk of nosocomial Legionellosis and to implementing procedures to minimize the risk of Legionella spp. colonization.

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