Legionella and Waterborne Disease

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Bacterial Pathogens".

Deadline for manuscript submissions: closed (10 April 2025) | Viewed by 6349

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Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy
Interests: healthcare; healthcare quality; health management; hospital management
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Special Issue Information

Dear Colleagues,

Legionella bacteria naturally occur in freshwater environments like lakes and rivers. However, they can also thrive in human-made water systems such as cooling towers, hot tubs, plumbing networks, and decorative fountains. They, primarily Legionella pneumophila, can lead to waterborne diseases when they contaminate water systems and are subsequently inhaled by humans. In Europe, Australia, and the USA, an estimated 10 to 15 cases of Legionellosis per million individuals are officially reported annually. However, in numerous countries, the limited availability of diagnostic tools and surveillance infrastructure leads to an uncertain assessment of its occurrence. The implementation of water management programs to identify Legionella and take steps to minimize the growth and transmission of Legionella are the most critical measures to prevent and control Legionellosis. We invite you to submit original research and review articles related to the issue of Legionella and waterborne diseases. Potential topics include, but are not limited to, the following:

  • Epidemiology: the patterns of Legionellosis occurrence, such as geographic distribution and trends over time.
  • Microbiology: the genetic diversity, growth conditions, antimicrobial resistance, and virulence of the bacteria.
  • Clinical Manifestations: symptoms, disease severity, and the factors that influence whether an infected individual develops Legionnaires' disease or Pontiac fever.
  • Diagnosis: the development of laboratory tests to detect Legionella bacteria or antibodies in patient samples.
  • Prevention: strategies for controlling Legionella contamination in water systems, including the use of disinfection techniques, temperature control, and water management plans.
  • Treatment: effective treatments for Legionellosis, such as studying the susceptibility of different Legionella strains to various antibiotics and identifying factors that may impact treatment outcomes.
  • Public Health Policy: the regulations and guidelines of water safety, outbreak response, public health messaging, environmental monitoring, and policy evaluation.

Dr. Angelo Baggiani
Guest Editor

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Keywords

  • Legionella
  • waterborne disease
  • environment
  • Legionnaires' disease
  • Pontiac fever

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Published Papers (4 papers)

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Research

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15 pages, 1258 KiB  
Article
Seasonal Dynamics and Legionellosis-Associated Hospitalization in Spain: A Retrospective Study
by Enrique Gea-Izquierdo, Rossana Ruiz-Urbaez, Valentín Hernández-Barrera and Ángel Gil-de-Miguel
Pathogens 2025, 14(5), 411; https://doi.org/10.3390/pathogens14050411 - 24 Apr 2025
Viewed by 488
Abstract
Legionellosis is a serious respiratory disease with a high mortality rate, particularly if it is untreated or occurs in the immunocompromised. Legionellosis must be reported in the Spanish Epidemiological Surveillance System. To optimize the epidemiologic knowledge of legionellosis and improve prevention, we have [...] Read more.
Legionellosis is a serious respiratory disease with a high mortality rate, particularly if it is untreated or occurs in the immunocompromised. Legionellosis must be reported in the Spanish Epidemiological Surveillance System. To optimize the epidemiologic knowledge of legionellosis and improve prevention, we have investigated whether the disease is associated with seasonality. This study has described legionellosis cases, the temporal trend by seasonality, hospitalization rate, case fatality rate, and costs by autonomous community and season. We retrospectively reviewed cases of legionellosis, documented patient and clinical characteristics, diagnostics, and seasonality of infection. This study combined national legionellosis notification and hospital discharge data that were linked via the Spanish National Health Service to provide a dataset of hospitalized cases occurring between 2002 and 2021 in Spain. There was a significant increase in the number of legionellosis cases due to the season of the year in Spain. An association between legionellosis and factors related to seasonality is suggested. An increasing trend in case fatality rate, seasonality, and regionality and a decrease in legionellosis hospitalization in Spain were identified. The characterization of changes in legionellosis trend and seasonality and timely synchronization and harmonization of hospitalization records are essential to strengthen disease monitoring and inform potential interventions in an epidemiological way. Full article
(This article belongs to the Special Issue Legionella and Waterborne Disease)
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17 pages, 2402 KiB  
Article
Occurrence of Uncultured Legionella spp. in Treated Wastewater Effluent and Its Impact on Human Health (SCA.Re.S Project)
by Osvalda De Giglio, Giusy Diella, Francesco Bagordo, Antonella Francesca Savino, Angelantonio Calabrese, Mariavirginia Campanale, Francesco Triggiano, Francesca Apollonio, Valentina Spagnuolo, Marco Lopuzzo, Tiziana Grassi, Maria Clementina Caputo, Silvia Brigida, Federica Valeriani, Vincenzo Romano Spica and Maria Teresa Montagna
Pathogens 2024, 13(9), 786; https://doi.org/10.3390/pathogens13090786 - 12 Sep 2024
Viewed by 1597
Abstract
Wastewater treatment plants (WWTPs) provide optimal conditions for the environmental spread of Legionella. As part of the Evaluation of Sanitary Risk Related to the Discharge of Wastewater to the Ground (SCA.Re.S) project, this study was conducted to evaluate the presence of Legionella [...] Read more.
Wastewater treatment plants (WWTPs) provide optimal conditions for the environmental spread of Legionella. As part of the Evaluation of Sanitary Risk Related to the Discharge of Wastewater to the Ground (SCA.Re.S) project, this study was conducted to evaluate the presence of Legionella in WWTP effluent and in groundwater samples collected from two wells located downstream from the plant. The samples were analyzed to determine the concentrations of Legionella spp using the standard culture-based method and molecular techniques, followed by genomic sequencing analysis. Legionella was detected only with the molecular methods (except in one sample of effluent positive for L. pneumophila serogroup 6), which showed viable Legionella pneumophila and L. non-pneumophila through the use of free DNA removal solution in both the effluent and groundwater, with concentrations that progressively decreased downstream from the plant. Viable L. pneumophila appeared to be slightly more concentrated in warm months. However, no significant differences (p ≥ 0.05) in concentrations between cold and warm months were observed. A genotypic analysis characterized the species present in the samples and found that uncultured Legionella spp, as yet undefined, constituted the prevalent species in all the samples (range 77.15–83.17%). WWTPs play an important role in the hygienic and sanitary quality of groundwater for different uses. The application of Legionella control systems during the purification of effluents is warranted to prevent possible outbreaks of legionellosis. Full article
(This article belongs to the Special Issue Legionella and Waterborne Disease)
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15 pages, 2949 KiB  
Article
Effects of Copper on Legionella pneumophila Revealed via Viability Assays and Proteomics
by Yang Song, Didier Mena-Aguilar, Connor L. Brown, William J. Rhoads, Richard F. Helm, Amy Pruden and Marc A. Edwards
Pathogens 2024, 13(7), 563; https://doi.org/10.3390/pathogens13070563 - 3 Jul 2024
Viewed by 1611
Abstract
Cu is an antimicrobial that is commonly applied to premise (i.e., building) plumbing systems for Legionella control, but the precise mechanisms of inactivation are not well defined. Here, we applied a suite of viability assays and mass spectrometry-based proteomics to assess the mechanistic [...] Read more.
Cu is an antimicrobial that is commonly applied to premise (i.e., building) plumbing systems for Legionella control, but the precise mechanisms of inactivation are not well defined. Here, we applied a suite of viability assays and mass spectrometry-based proteomics to assess the mechanistic effects of Cu on L. pneumophila. Although a five- to six-log reduction in culturability was observed with 5 mg/L Cu2+ exposure, cell membrane integrity only indicated a <50% reduction. Whole-cell proteomic analysis revealed that AhpD, a protein related to oxidative stress, was elevated in Cu-exposed Legionella relative to culturable cells. Other proteins related to cell membrane synthesis and motility were also higher for the Cu-exposed cells relative to controls without Cu. While the proteins related to primary metabolism decreased for the Cu-exposed cells, no significant differences in the abundance of proteins related to virulence or infectivity were found, which was consistent with the ability of VBNC cells to cause infections. Whereas the cell-membrane integrity assay provided an upper-bound measurement of viability, an amoebae co-culture assay provided a lower-bound limit. The findings have important implications for assessing Legionella risk following its exposure to copper in engineered water systems. Full article
(This article belongs to the Special Issue Legionella and Waterborne Disease)
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Review

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19 pages, 817 KiB  
Review
The Adequacy of Current Legionnaires’ Disease Diagnostic Practices in Capturing the Epidemiology of Clinically Relevant Legionella: A Scoping Review
by Ryan Ha, Ashley Heilmann, Sylvain A. Lother, Christine Turenne, David Alexander, Yoav Keynan and Zulma Vanessa Rueda
Pathogens 2024, 13(10), 857; https://doi.org/10.3390/pathogens13100857 - 1 Oct 2024
Cited by 1 | Viewed by 1870
Abstract
Legionella is an underdiagnosed and underreported etiology of pneumonia. Legionella pneumophila serogroup 1 (LpSG1) is thought to be the most common pathogenic subgroup. This assumption is based on the frequent use of a urinary antigen test (UAT), only capable of diagnosing LpSG1. We [...] Read more.
Legionella is an underdiagnosed and underreported etiology of pneumonia. Legionella pneumophila serogroup 1 (LpSG1) is thought to be the most common pathogenic subgroup. This assumption is based on the frequent use of a urinary antigen test (UAT), only capable of diagnosing LpSG1. We aimed to explore the frequency of Legionella infections in individuals diagnosed with pneumonia and the performance of diagnostic methods for detecting Legionella infections. We conducted a scoping review to answer the following questions: (1) “Does nucleic acid testing (NAT) increase the detection of non-pneumophila serogroup 1 Legionella compared to non-NAT?”; and (2) “Does being immunocompromised increase the frequency of pneumonia caused by non-pneumophila serogroup 1 Legionella compared to non-immunocompromised individuals with Legionnaires’ disease (LD)?”. Articles reporting various diagnostic methods (both NAT and non-NAT) for pneumonia were extracted from several databases. Of the 3449 articles obtained, 31 were included in our review. The most common species were found to be L. pneumophila, L. longbeachae, and unidentified Legionella species appearing in 1.4%, 0.9%, and 0.6% of pneumonia cases. Nearly 50% of cases were caused by unspecified species or serogroups not detected by the standard UAT. NAT-based techniques were more likely to detect Legionella than non-NAT-based techniques. The identification and detection of Legionella and serogroups other than serogroup 1 is hampered by a lack of application of broader pan-Legionella or pan-serogroup diagnostics. Full article
(This article belongs to the Special Issue Legionella and Waterborne Disease)
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