Waterborne Pathogens: Epidemiology, Surveillance, Control and Risk

A topical collection in Pathogens (ISSN 2076-0817). This collection belongs to the section "Epidemiology of Infectious Diseases".

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Editors

Department of Public Health and Pediatrics, University of Torino, Via Santena 5bis, 10126 Torino, Italy
Interests: methods for the detection of Legionella in water; study of disinfection method against waterborne pathogens; evaluation of microbiological air quality
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Waterborne diseases are a major global problem, associated with high morbidity and mortality, and massive economic costs; they are responsible for between 1.6 and 12 million deaths annually. Although the burden is the highest in developing countries, outbreaks of the disease still occur in developed countries. In the USA, in 2013–2014, 42 drinking water-associated outbreaks were reported, accounting for at least 1006 cases of illness, 124 hospitalizations, and 13 deaths.  In developed countries, waterborne pathogens include classic and emerging bacteria (e.g. pathogenic Escherichia coli, Salmonella spp., Campylobacter spp., Legionella), viruses (e.g. norovirus, adenovirus) and protozoa (Cryptosporidium spp. and Giardia spp.). Emerging pathogens have lately had an increased interest from the scientific community, and they are now considered to be a major microbiologic public health threat, including antibiotic resistant bacteria. The main causes for drinking water contamination can be the intrusion of animal feces or wastewater due to heavy rain; discharge of wastewater into the water source; malfunctioning of the disinfection equipment in the treatment plants and cross-connections; pipe breaks and wastewater intrusion into the network. The environmental monitoring of pathogens in water and wastewater is an essential tool for detecting and preventing or minimizing the further spread of this microorganisms. Currently, conventional methods based on a culture approach are used to detect pathogens, however, they have several limits, including lengthy experimental turnaround times for results. For this reason, in recent decades, alternative tools for the rapid, sensitive, and specific detection of pathogens in water and wastewater samples have been proposed (e.g., real-time PCR, biosensors). Moreover, studies leveraging next-generation sequencing (NGS) technologies are providing new insights into the ecology of microbially mediated processes that influence pathogen dissemination.

We invite you to submit a review article or original research article related to these issues.

Potential topics include, but are not limited to:

- Waterborne pathogens occurrence in environment (e.g. wastewater, water distribution system, surface water);

- Risk assessment of waterborne pathogens;

- Effectiveness of control procedures in reducing waterborne pathogens contamination; 

- New methods for the detection of waterborne pathogen;

- Role of climate changes in waterborne pathogen spreading.

Dr. Silvia Bonetta
Dr. Sara Bonetta
Collection Editors

Manuscript Submission Information

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Keywords

  • Water environment
  • Environmental monitoring
  • Detection methods
  • Control procedures
  • Climate changes
  • Risk assessment

Related Special Issue

Published Papers (22 papers)

2022

Jump to: 2021, 2020, 2019

15 pages, 1625 KiB  
Article
The Geological Characteristics of the Vadose Zone Influence the Impact of Treated Wastewater on the Groundwater Quality (SCA.Re.S. Project 2019–2020)
by Osvalda De Giglio, Francesco Triggiano, Francesca Apollonio, Chrysovalentinos Pousis, Carla Calia, Giusy Diella, Francesco Bagordo, Sapia Murgolo, Tiziana Grassi, Cristina De Ceglie, Silvia Brigida, Giuseppina La Rosa, Pamela Mancini, Giusy Bonanno Ferraro, Antonella De Donno, Giuseppe Mascolo, Maria Clementina Caputo and Maria Teresa Montagna
Pathogens 2022, 11(6), 677; https://doi.org/10.3390/pathogens11060677 - 11 Jun 2022
Cited by 1 | Viewed by 1647
Abstract
This study evaluated whether some chemical and microbial contaminants in treated sewage effluents from two wastewater treatment plants (WWTP) reached the groundwater when they drained through a fractured karst vadose zone (WWTP-K) and a porous vadose zone (WWTP-P). Forty-five samples of sewage water [...] Read more.
This study evaluated whether some chemical and microbial contaminants in treated sewage effluents from two wastewater treatment plants (WWTP) reached the groundwater when they drained through a fractured karst vadose zone (WWTP-K) and a porous vadose zone (WWTP-P). Forty-five samples of sewage water (SW), treated water (TW), and monitoring well (MW), collected from WWTP-P (24) and WWTP-K (21), were analyzed for a range of microbiological and chemical properties. The E. coli and Salmonella counts were below the limits outlined in the Legislative Decree 152/06 in effluents from both types of WWTP. Enteric viruses were found in 37.5% and 12.5% of the SW and TW from WWTP-P, respectively. The percentages of Pepper mild mottle virus isolated were higher in TW (62.5% in WWTP-P, 85.7% in WWTP-K) than in SW and MW. The residual concentrations of contaminants of emerging concern (CEC) of each drug category were higher in the MW downstream of WWTP-K than of WWTP-P. Our results showed that the porous vadose zone was more effective at reducing the contaminant loads than the fractured karst one, especially the CEC, in the effluent. The legislation should include other parameters to minimize the risks from treated effluent that is discharged to soil. Full article
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13 pages, 846 KiB  
Article
Irrigation of Olives with Reclaimed Wastewaters and Deficit Strategies Affect Pathogenic Bacteria Contamination of Water and Soil
by Gaetano Alessandro Vivaldi, Salvatore Camposeo, Gabriele Caponio, Giuseppe Lopriore, Francesco Discipio, Francesca Apollonio, Francesco Triggiano, Osvalda De Giglio and Maria Teresa Montagna
Pathogens 2022, 11(5), 488; https://doi.org/10.3390/pathogens11050488 - 20 Apr 2022
Cited by 3 | Viewed by 1675
Abstract
This study aimed to evaluate pathogenic bacterial contamination of the water-soil-plant system in potted olive trees irrigated with reclaimed wastewater. Desalinated water (DW) obtained by treating municipal wastewater (SW) and reclaimed water (RW) obtained by mixing SW with the brine (BR) produced by [...] Read more.
This study aimed to evaluate pathogenic bacterial contamination of the water-soil-plant system in potted olive trees irrigated with reclaimed wastewater. Desalinated water (DW) obtained by treating municipal wastewater (SW) and reclaimed water (RW) obtained by mixing SW with the brine (BR) produced by DESERT technology (tertiary treatment by ultrafiltration, active carbon and reverse osmosis) were used. Two different irrigation regimes were compared: full irrigation (FI) and regulated deficit irrigation (RDI). During two irrigation seasons the concentrations of Escherichia coli, enterococci, spores of sulfite-reducing Clostridia (SRC) and Salmonella spp. were monitored in water, soil and fruit samples. Microbial concentrations in DW were always below the threshold for reuse in agriculture, while RW showed the highest level of contamination for all observed parameters. RDI management appeared to increase the soil content of SRC spores with respect to FI. Sporadically low SRC spore contamination was recorded in some fruits only in 2018, regardless of the irrigation source, probably because of accidental contamination during sampling or post-harvest handling. This study encourages the creation of a better regulatory framework reference, with specific guidelines for the use of RW as part of integrated environmental systems for the management of sustainable agriculture. Full article
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8 pages, 227 KiB  
Article
Desiccation-Tolerance of Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium chimaera, Mycobacterium abscessus and Mycobacterium chelonae
by Joseph O. Falkinham III and Myra D. Williams
Pathogens 2022, 11(4), 463; https://doi.org/10.3390/pathogens11040463 - 13 Apr 2022
Cited by 2 | Viewed by 1394
Abstract
Desiccation-tolerance of cells of four strains of Mycobacterium chimaera and individual strains of Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium abscessus, and Mycobacterium chelonae were measured by two methods. The survival of water-acclimated cells both in filter paper and on the surface [...] Read more.
Desiccation-tolerance of cells of four strains of Mycobacterium chimaera and individual strains of Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium abscessus, and Mycobacterium chelonae were measured by two methods. The survival of water-acclimated cells both in filter paper and on the surface of stainless-steel coupons were measured. In filter paper at 40% relative humidity at 25 °C, survival of patient isolates of M. avium and M. chimaera cells was 28% and 34% after 21 days of incubation, whereas it was 100% for the Sorin 3T isolate of M. chimaera. On stainless-steel biofilms after 42 days of incubation at 40% relative humidity at 25 °C, survival of water-acclimated cells of M. intracellulare was above 100%, while M. chelonae cells did not survive beyond 21 days, and survival of water-acclimated cells of M. avium and M. abscessus was 18% and 14%, respectively. On stainless-steel coupons, survival of patient and Sorin 3T isolates of M. chimaera was quite similar, specifically between 14% and 28% survival, after 42 days of incubation at 40% relative humidity at 25 °C. The experiments would support the hypothesis that some nontuberculous mycobacterial species are relatively desiccation-tolerant, whereas others are not. Further, long-term survival of the two M. chimaera strains is consistent with the presence of that species in Sorin 3T heater-coolers shipped throughout the world. Full article
8 pages, 1870 KiB  
Article
Low Efficacy of Periodical Thermal Shock for Long-Term Control of Legionella spp. in Hot Water System of Hotels
by Jhon J. Molina, Magdalena Bennassar, Edwin Palacio and Sebastian Crespi
Pathogens 2022, 11(2), 152; https://doi.org/10.3390/pathogens11020152 - 25 Jan 2022
Cited by 6 | Viewed by 2671
Abstract
Different guidelines and regulations for the prevention of legionellosis in public facilities include the recommendation of a periodical thermal shock in the hot water system. The purpose of this study was to assess the efficacy of periodical thermal shocks along a 1-year period [...] Read more.
Different guidelines and regulations for the prevention of legionellosis in public facilities include the recommendation of a periodical thermal shock in the hot water system. The purpose of this study was to assess the efficacy of periodical thermal shocks along a 1-year period on the presence of Legionella spp. in the domestic hot water system of hotels. The Legionella testing results from the period January–December 2019 coming from a group of 77 hotel facilities in the Balearic Islands (Spain) conducting periodical thermal shocks were analyzed. A second group of 44 hotels operating without periodical thermal shocks was used for a comparative analysis. In the facilities where the periodical thermal shock was performed, 16.0% of the results (429 hot water samples collected) were positive for Legionella spp., compared to 21.1% (298 samples), where periodical thermal shock was not performed. Overall, in the thermal shock group, 32.5% of the sites presented at least 1 positive sample along the period of study versus 45.5% in the control group. None of these differences was statistically significant (p-value > 0.05). These findings suggest that the efficacy of regular thermal shock for long-term control of Legionella spp. in domestic hot water systems of hotels is low. Full article
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2021

Jump to: 2022, 2020, 2019

15 pages, 3834 KiB  
Article
Occurrence of Legionella spp. in Man-Made Water Sources: Isolates Distribution and Phylogenetic Characterization in the Emilia-Romagna Region
by Marta Mazzotta, Silvano Salaris, Maria Rosaria Pascale, Luna Girolamini and Sandra Cristino
Pathogens 2021, 10(5), 552; https://doi.org/10.3390/pathogens10050552 - 03 May 2021
Cited by 11 | Viewed by 2028
Abstract
Legionella species distribution in the Emilia-Romagna region, involving hospital (H) and community (C) environments, was conducted. Legionella culture, agglutination test, and mip-gene sequencing were applied on 240 isolates. The analysis showed a higher prevalence of non-Legionellapneumophila (n-Lp) species [...] Read more.
Legionella species distribution in the Emilia-Romagna region, involving hospital (H) and community (C) environments, was conducted. Legionella culture, agglutination test, and mip-gene sequencing were applied on 240 isolates. The analysis showed a higher prevalence of non-Legionellapneumophila (n-Lp) species (84.1%) compared with L. pneumophila (Lp) (15.9%), with a higher frequency of n-Lp with respect to Lp species in both environments (77.6% and 96.4%, in H and C, respectively). The Shannon index showed a significant difference in Legionella distribution (p = 0.00017), with a significant abundance of Lp in the H compared with C environment (p = 0.00028). The continuous disinfection treatment in H could contribute to adaptive survival of the Lp species. Phylogenetic analysis revealed a conservative clade distribution between H and C: L. feeleii clade with three subclades in C and the Lp clade with five subclades in H and two in C, respectively. Our findings suggest the importance of Legionella surveillance both in H and C, with a focus on n-Lp species less connected to human disease. The Legionella prevalence and diversity found here indicate that geographical and temporal isolate evolution should be considered during surveillance, particularly in the light of global warming and changes in population risk factors. Full article
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2020

Jump to: 2022, 2021, 2019

6 pages, 224 KiB  
Editorial
Editorial Comments to the Special Issue: “Legionella Contamination in Water Environment”
by Silvia Bonetta and Sara Bonetta
Pathogens 2020, 9(12), 1017; https://doi.org/10.3390/pathogens9121017 - 02 Dec 2020
Cited by 1 | Viewed by 1595
Abstract
Legionella spp [...] Full article
23 pages, 3778 KiB  
Article
Biogeography and Environmental Drivers of Legionella pneumophila Abundance and Genotype Composition across the West Bank: Relevance of a Genotype-Based Ecology for Understanding Legionella Occurrence
by Ashraf R. Zayed, Suha Butmeh, Marina Pecellin, Alaa Salah, Hanna Alalam, Michael Steinert, Manfred G. Höfle, Dina M. Bitar and Ingrid Brettar
Pathogens 2020, 9(12), 1012; https://doi.org/10.3390/pathogens9121012 - 01 Dec 2020
Cited by 10 | Viewed by 1982
Abstract
The West Bank can be considered as a high-risk area for Legionella prevalence in drinking water due to high ambient temperature, intermittent water supply, frequent pressure loss, and storage of drinking water in roof containers. To assess occurrence of Legionella species, especially L. [...] Read more.
The West Bank can be considered as a high-risk area for Legionella prevalence in drinking water due to high ambient temperature, intermittent water supply, frequent pressure loss, and storage of drinking water in roof containers. To assess occurrence of Legionella species, especially L. pneumophila, in the drinking water of the West Bank, the drinking water distribution systems of eight hospitals were sampled over a period of 2.3 years covering the seasonal cycle and the major geographic regions. To gain insight into potential environmental drivers, a set of physico-chemical and microbiological parameters was recorded. Sampling included drinking water and biofilm analyzed by culture and PCR-based methods. Cultivation led to the isolation of 180 strains of L. pneumophila that were genotyped by Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA). Surprisingly, the abundance of culturable L. pneumophila was low in drinking water of the sampling sites, with only three out of eight sites where Legionella was observed at all (range: 30–500 CFU/Liter). By contrast, biofilm and PCR-based analyses showed a higher prevalence. Statistical analyses with physico-chemical parameters revealed a decrease of L. pneumophila abundance for water and biofilm with increasing magnesium concentrations (>30 mg/L). MLVA-genotype analysis of the L. pneumophila isolates and their spatial distribution indicated three niches characterized by distinct physico-chemical parameters and inhabited by specific consortia of genotypes. This study provides novel insights into mechanisms shaping L. pneumophila populations and triggering their abundance leading to an understanding of their genotype-specific niches and ecology in support of improved prevention measures. Full article
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34 pages, 2696 KiB  
Review
Critical Review: Propensity of Premise Plumbing Pipe Materials to Enhance or Diminish Growth of Legionella and Other Opportunistic Pathogens
by Abraham C. Cullom, Rebekah L. Martin, Yang Song, Krista Williams, Amanda Williams, Amy Pruden and Marc A. Edwards
Pathogens 2020, 9(11), 957; https://doi.org/10.3390/pathogens9110957 - 17 Nov 2020
Cited by 37 | Viewed by 6596
Abstract
Growth of Legionella pneumophila and other opportunistic pathogens (OPs) in drinking water premise plumbing poses an increasing public health concern. Premise plumbing is constructed of a variety of materials, creating complex environments that vary chemically, microbiologically, spatially, and temporally in a manner likely [...] Read more.
Growth of Legionella pneumophila and other opportunistic pathogens (OPs) in drinking water premise plumbing poses an increasing public health concern. Premise plumbing is constructed of a variety of materials, creating complex environments that vary chemically, microbiologically, spatially, and temporally in a manner likely to influence survival and growth of OPs. Here we systematically review the literature to critically examine the varied effects of common metallic (copper, iron) and plastic (PVC, cross-linked polyethylene (PEX)) pipe materials on factors influencing OP growth in drinking water, including nutrient availability, disinfectant levels, and the composition of the broader microbiome. Plastic pipes can leach organic carbon, but demonstrate a lower disinfectant demand and fewer water chemistry interactions. Iron pipes may provide OPs with nutrients directly or indirectly, exhibiting a high disinfectant demand and potential to form scales with high surface areas suitable for biofilm colonization. While copper pipes are known for their antimicrobial properties, evidence of their efficacy for OP control is inconsistent. Under some circumstances, copper’s interactions with premise plumbing water chemistry and resident microbes can encourage growth of OPs. Plumbing design, configuration, and operation can be manipulated to control such interactions and health outcomes. Influences of pipe materials on OP physiology should also be considered, including the possibility of influencing virulence and antibiotic resistance. In conclusion, all known pipe materials have a potential to either stimulate or inhibit OP growth, depending on the circumstances. This review delineates some of these circumstances and informs future research and guidance towards effective deployment of pipe materials for control of OPs. Full article
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24 pages, 1648 KiB  
Article
Characterization of Legionella pneumophila Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank
by Ashraf R. Zayed, Marina Pecellin, Alaa Salah, Hanna Alalam, Suha Butmeh, Michael Steinert, Rene Lesnik, Ingrid Brettar, Manfred G. Höfle and Dina M. Bitar
Pathogens 2020, 9(11), 862; https://doi.org/10.3390/pathogens9110862 - 22 Oct 2020
Cited by 9 | Viewed by 3079
Abstract
The West Bank can be considered a high-risk area for Legionnaires’ disease (LD) due to its hot climate, intermittent water supply and roof storage of drinking water. Legionella, mostly L. pneumophila, are responsible for LD, a severe, community-acquired and nosocomial pneumonia. [...] Read more.
The West Bank can be considered a high-risk area for Legionnaires’ disease (LD) due to its hot climate, intermittent water supply and roof storage of drinking water. Legionella, mostly L. pneumophila, are responsible for LD, a severe, community-acquired and nosocomial pneumonia. To date, no extensive assessment of Legionella spp and L. pneumophila using cultivation in combination with molecular approaches in the West Bank has been published. Two years of environmental surveillance of Legionella in water and biofilms in the drinking water distribution systems (DWDS) of eight hospitals was carried out; 180 L. pneumophila strains were isolated, mostly from biofilms in DWDS. Most of the isolates were identified as serogroup (Sg) 1 (60%) and 6 (30%), while a minor fraction comprised Sg 8 and 10. Multilocus Variable number of tandem repeats Analysis using 13 loci (MLVA-8(12)) was applied as a high-resolution genotyping method and compared to the standard Sequence Based Typing (SBT). The isolates were genotyped in 27 MLVA-8(12) genotypes (Gt), comprising four MLVA clonal complexes (VACC 1; 2; 5; 11). The major fraction of isolates constituted Sequence Type (ST)1 and ST461. Most of the MLVA-genotypes were highly diverse and often unique. The MLVA-genotype composition showed substantial regional variability. In general, the applied MLVA-method made it possible to reproducibly genotype the isolates, and was consistent with SBT but showed a higher resolution. The advantage of the higher resolution was most evident for the subdivision of the large strain sets of ST1 and ST461; these STs were shown to be highly pneumonia-relevant in a former study. This shows that the resolution by MLVA is advantageous for back-tracking risk sites and for the avoidance of outbreaks of L. pneumophila. Overall, our results provide important insights into the detailed population structure of L. pneumophila, allowing for better risk assessment for DWDS. Full article
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6 pages, 439 KiB  
Article
Evaluation of GVPC and BCYE Media for Legionella Detection and Enumeration in Water Samples by ISO 11731: Does Plating on BCYE Medium Really Improve Yield?
by Maria Scaturro, Elisa Poznanski, Mariarosaria Mupo, Paola Blasior, Margit Seeber, Anna-Maria Prast, Elisa Romanin, Antonietta Girolamo, Maria Cristina Rota, Antonino Bella, Maria Luisa Ricci and Alberta Stenico
Pathogens 2020, 9(9), 757; https://doi.org/10.3390/pathogens9090757 - 16 Sep 2020
Cited by 8 | Viewed by 4033
Abstract
Legionella spp are the causative agents of Legionnaires’ diseases, which is a pneumonia of important public health concern. Ubiquitous freshwater and soil inhabitants can reach man-made water systems and cause illness. Legionella enumeration and quantification in water systems is crucial for risk assessment [...] Read more.
Legionella spp are the causative agents of Legionnaires’ diseases, which is a pneumonia of important public health concern. Ubiquitous freshwater and soil inhabitants can reach man-made water systems and cause illness. Legionella enumeration and quantification in water systems is crucial for risk assessment and culture examination is the gold standard method. In this study, Legionella recovery from potable water samples, at presumably a low concentration of interfering microorganisms, was compared by plating on buffered charcoal yeast extract (BCYE) and glycine, vancomycin, polymyxin B, cycloheximide (GVPC) Legionella agar media, according to the International Standard Organization (ISO) 11731: 2017. Overall, 556 potable water samples were analyzed and 151 (27.1%) were positive for Legionella. Legionella grew on both BCYE and GVPC agar plates in 85/151 (56.3%) water samples, in 65/151 (43%) on only GVPC agar plates, and in 1/151 (0.7%) on only BCYE agar plates. In addition, GVPC medium identified Legionella species other than pneumophila in six more samples as compared with the culture on BCYE. Although the medians of colony forming units per liter (CFU/L) detected on the BCYE and GVPC agar plates were 2500 and 1350, respectively (p-value < 0.0001), the difference did not exceed one logarithm, and therefore is not relevant for Legionella risk assessment. These results make questionable the need to utilize BCYE agar plates to analyze potable water samples. Full article
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17 pages, 3472 KiB  
Article
Interactive Effects of Copper Pipe, Stagnation, Corrosion Control, and Disinfectant Residual Influenced Reduction of Legionella pneumophila during Simulations of the Flint Water Crisis
by Rebekah L. Martin, Owen R. Strom, Amy Pruden and Marc A. Edwards
Pathogens 2020, 9(9), 730; https://doi.org/10.3390/pathogens9090730 - 04 Sep 2020
Cited by 19 | Viewed by 4031
Abstract
Flint, MI experienced two outbreaks of Legionnaires’ Disease (LD) during the summers of 2014 and 2015, coinciding with use of Flint River as a drinking water source without corrosion control. Using simulated distribution systems (SDSs) followed by stagnant simulated premise (i.e., building) plumbing [...] Read more.
Flint, MI experienced two outbreaks of Legionnaires’ Disease (LD) during the summers of 2014 and 2015, coinciding with use of Flint River as a drinking water source without corrosion control. Using simulated distribution systems (SDSs) followed by stagnant simulated premise (i.e., building) plumbing reactors (SPPRs) containing cross-linked polyethylene (PEX) or copper pipe, we reproduced trends in water chemistry and Legionella proliferation observed in the field when Flint River versus Detroit water were used before, during, and after the outbreak. Specifically, due to high chlorine demand in the SDSs, SPPRs with treated Flint River water were chlorine deficient and had elevated L. pneumophila numbers in the PEX condition. SPPRs with Detroit water, which had lower chlorine demand and higher residual chlorine, lost all culturable L. pneumophila within two months. L. pneumophila also diminished more rapidly with time in Flint River SPPRs with copper pipe, presumably due to the bacteriostatic properties of elevated copper concentrations caused by lack of corrosion control and stagnation. This study confirms hypothesized mechanisms by which the switch in water chemistry, pipe materials, and different flow patterns in Flint premise plumbing may have contributed to observed LD outbreak patterns. Full article
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8 pages, 241 KiB  
Article
Performance of Legiolert Test vs. ISO 11731 to Confirm Legionella pneumophila Contamination in Potable Water Samples
by Maria Scaturro, Matteo Buffoni, Antonietta Girolamo, Sandra Cristino, Luna Girolamini, Marta Mazzotta, Maria Antonietta Bucci Sabattini, Cristina Maria Zaccaro, Leonarda Chetti, Microbiology Arpa Novara Laboratory, Antonino Bella, Maria Cristina Rota and Maria Luisa Ricci
Pathogens 2020, 9(9), 690; https://doi.org/10.3390/pathogens9090690 - 23 Aug 2020
Cited by 19 | Viewed by 3296
Abstract
Detection and enumeration of Legionella in water samples is of great importance for risk assessment analysis. The plate culture method is the gold standard, but has received several well-known criticisms, which have induced researchers to develop alternative methods. The purpose of this study [...] Read more.
Detection and enumeration of Legionella in water samples is of great importance for risk assessment analysis. The plate culture method is the gold standard, but has received several well-known criticisms, which have induced researchers to develop alternative methods. The purpose of this study was to compare Legionella counts obtained by the analysis of potable water samples through the plate culture method and through the IDEXX liquid culture Legiolert method. Legionella plate culture, according to ISO 11731:1998, was performed using 1 L of water. Legiolert was performed using both the 10 mL and 100 mL Legiolert protocols. Overall, 123 potable water samples were analyzed. Thirty-seven (30%) of them, positive for L. pneumophila, serogroups 1 or 2–14 by plate culture, were used for comparison with the Legiolert results. The Legiolert 10 mL test detected 34 positive samples (27.6%) and the Legiolert 100 mL test detected 37 positive samples, 27.6% and 30% respectively, out of the total samples analyzed. No significant difference was found between either the Legiolert 10 mL and Legiolert 100 mL vs. the plate culture (p = 0.9 and p = 0.3, respectively) or between the Legiolert 10 mL and Legiolert 100 mL tests (p = 0.83). This study confirms the reliability of the IDEXX Legiolert test for Legionella pneumophila detection and enumeration, as already shown in similar studies. Like the plate culture method, the Legiolert assay is also suitable for obtaining isolates for typing purposes, relevant for epidemiological investigations. Full article
29 pages, 2943 KiB  
Article
Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System
by Helen Y. Buse, Brian J. Morris, Vicente Gomez-Alvarez, Jeffrey G. Szabo and John S. Hall
Pathogens 2020, 9(7), 567; https://doi.org/10.3390/pathogens9070567 - 13 Jul 2020
Cited by 17 | Viewed by 2963
Abstract
Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18–28 months at [...] Read more.
Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18–28 months at six locations differing in plumbing material and potable water age, quality, and usage. A total of 114 bulk water and 57 biofilm samples were analyzed. Legionella culturability fluctuated seasonally with most culture-positive samples being collected during the winter compared to the spring, summer, and fall months. Positive and negative correlations between Legionella and L. pneumophila occurrence and other physiochemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 presumptive Legionella isolates, from four locations across three time points, identified nine isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; three as L. pneumophila sg5 ST1950 and ST2037; six as L. feeleii; and one as Ochrobactrum. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence at four and two locations, respectively. Viewed collectively with similar studies, this information will enable a better understanding of the engineering, operational, and water quality parameters supporting Legionella growth within BWSs. Full article
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9 pages, 236 KiB  
Article
Sensitivity and Selectivity of Two Commercially Available Media for Legionella spp. Recovery from Environmental Water Samples
by Savina Ditommaso, Monica Giacomuzzi, Gabriele Memoli, Jacopo Garlasco and Carla M. Zotti
Pathogens 2020, 9(7), 523; https://doi.org/10.3390/pathogens9070523 - 29 Jun 2020
Cited by 3 | Viewed by 2729
Abstract
The quality control of culture media used for Legionella spp. isolation and enumeration is paramount to achieve a satisfactory degree of comparability among water testing results from different laboratories. Here, we report on a comparative assessment of the sensitivity and selectivity of MWY [...] Read more.
The quality control of culture media used for Legionella spp. isolation and enumeration is paramount to achieve a satisfactory degree of comparability among water testing results from different laboratories. Here, we report on a comparative assessment of the sensitivity and selectivity of MWY and BCYEα media supplied by two different manufacturers (i.e., Xebios Diagnostics GmbH and Oxoid Ltd) for the detection of Legionella spp. from environmental water samples. Even though our analysis showed an excellent agreement between the recovery rates of the four media tested (90.5%), the quantitative recovery of Legionella spp. colonies using Xebios media was significantly greater than that achieved by Oxoid media (P = 0.0054). Furthermore, the sensitivity of detection was significantly higher when samples were plated on MWY Xebios agar (P = 0.0442), while the selectivity of MWY appeared to be the same regardless of the manufacturer. Furthermore, MWYXebios agar favored the growth of much larger colonies compared to those observed on MWYOxoid agar. Finally, MWYXebios medium enhanced the recovery of non-pneumophila Legionella species. Collectively, our findings demonstrate that quality control is crucial to ensure high selectivity and sensitivity of the culture media used for the detection and enumeration of Legionella spp. from environmental water resources. As water remediation measures strictly depend on Legionella spp. recovery, culture protocol standardization, as well as quality control of the culture media, is essential to achieve intra- and interlaboratory reproducibility and accuracy. Full article
12 pages, 1085 KiB  
Article
Mitigation of Expression of Virulence Genes in Legionella pneumophila Internalized in the Free-Living Amoeba Willaertia magna C2c Maky
by Rayane Mouh Mameri, Jacques Bodennec, Laurent Bezin and Sandrine Demanèche
Pathogens 2020, 9(6), 447; https://doi.org/10.3390/pathogens9060447 - 05 Jun 2020
Cited by 4 | Viewed by 2243
Abstract
Legionella pneumophila is a human pathogen responsible for a severe form of pneumonia named Legionnaire disease. Its natural habitat is aquatic environments, being in a free state or intracellular parasites of free-living amoebae, such as Acanthamoeba castellanii. This pathogen is able to [...] Read more.
Legionella pneumophila is a human pathogen responsible for a severe form of pneumonia named Legionnaire disease. Its natural habitat is aquatic environments, being in a free state or intracellular parasites of free-living amoebae, such as Acanthamoeba castellanii. This pathogen is able to replicate within some amoebae. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to resist to L. pneumophila and even to be able to eliminate the L. pneumophila strains Philadelphia, Lens, and Paris. Here, we studied the induction of seven virulence genes of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky in comparison within A. castellanii and with the gene expression level of L. pneumophila strains alone used as controls. We defined a gene expression-based virulence index to compare easily and without bias the transcript levels in different conditions and demonstrated that W. magna C2c Maky did not increase the virulence of L. pneumophila strains in contrast to A. castellanii. These results confirmed the non-permissiveness of W. magna C2c Maky toward L. pneumophila strains. Full article
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17 pages, 1838 KiB  
Article
The Role of Sensor-Activated Faucets in Surgical Handwashing Environment as a Reservoir of Legionella
by Marta Mazzotta, Luna Girolamini, Maria Rosaria Pascale, Jessica Lizzadro, Silvano Salaris, Ada Dormi and Sandra Cristino
Pathogens 2020, 9(6), 446; https://doi.org/10.3390/pathogens9060446 - 05 Jun 2020
Cited by 6 | Viewed by 2419
Abstract
Surgical handwashing is a mandatory practice to protect both surgeons and patients in order to control Healthcare-Associated Infections (HAIs). The study is focused on Legionella and Pseudomonas aeruginosa contamination in Surgical Handwashing Outlets (SHWOs) provided by sensor-activated faucets with Thermostatic Mixer Valves (TMVs), [...] Read more.
Surgical handwashing is a mandatory practice to protect both surgeons and patients in order to control Healthcare-Associated Infections (HAIs). The study is focused on Legionella and Pseudomonas aeruginosa contamination in Surgical Handwashing Outlets (SHWOs) provided by sensor-activated faucets with Thermostatic Mixer Valves (TMVs), as correlated to temperature, technologies, and disinfection used. Samples were analyzed by standard culture techniques, comparing hot- and cold-water samples. Legionella isolates were typed by an agglutination test and by mip sequencing. Legionella contamination showed the same distribution between hot and cold samples concerning positive samples and mean concentration: 44.5% and 1.94 Log10 cfu/L vs. 42.6% and 1.81 Log10 cfu/L, respectively. Regarding the distribution of isolates (Legionella pneumophila vs. Legionella non-pneumophila species), significant differences were found between hot- and cold-positive samples. The contamination found in relation to ranges of temperature showed the main positive samples (47.1%) between 45.1–49.6 °C, corresponding to high Legionella concentrations (2.17 Log10 cfu/L). In contrast, an increase of temperature (>49.6 °C) led to a decrease in positive samples (23.2%) and mean concentration (1.64 Log10 cfu/L). A low level of Pseudomonas aeruginosa was found. For SHWOs located in critical areas, lack of consideration of technologies used and uncorrected disinfection protocols may lead to the development of a high-risk environment for both patients and surgeons. Full article
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14 pages, 879 KiB  
Article
A Snapshot of the Prevalence and Molecular Diversity of Legionella pneumophila in the Water Systems of Israeli Hotels
by Eugenia Yakunin, Eszter Kostyal, Vered Agmon, Itamar Grotto, Lea Valinsky and Jacob Moran-Gilad
Pathogens 2020, 9(6), 414; https://doi.org/10.3390/pathogens9060414 - 27 May 2020
Cited by 13 | Viewed by 2093
Abstract
Exposure to Legionella spp. contaminated aerosols in hotel settings confers risk for travel-associated Legionnaire’s disease (TALD). In this study, we investigated the prevalence of Legionella contamination and its molecular diversity in hotels and resorts across Israel. The study was comprised of a convenience [...] Read more.
Exposure to Legionella spp. contaminated aerosols in hotel settings confers risk for travel-associated Legionnaire’s disease (TALD). In this study, we investigated the prevalence of Legionella contamination and its molecular diversity in hotels and resorts across Israel. The study was comprised of a convenience sample of water systems from 168 hotels and resorts countrywide, routinely inspected between March 2015 and February 2017. Isolation and quantitation of Legionella were performed in a water laboratory using the ISO 11731 method. The distribution of Legionella isolates was analyzed according to geography and source. The genetic diversity of a subset of isolates was analyzed by sequence-based typing (SBT) at the National Reference Laboratory for Legionella and compared to the national database. Out of 2830 samples tested, 470 (17%) obtained from 102 different premises (60% of hotels) were positive for Legionella spp. In 230 samples (49% of all positive, 8% of total samples), accounting for 37% of hotels, Legionella spp. counts exceeded the regulatory threshold of 1000 CFU/L. The most frequently contaminated water sources were cooling towers (38%), followed by faucets, hot tubs, water lines, and storage tanks (14–17% each). Furthermore, 32% and 17% of samples obtained from cooling towers and hot tubs, respectively, exceeded the regulatory thresholds. SBT was performed on 78 strains and revealed 27 different sequence types (STs), including two novel STs. The most prevalent STs found were ST1 (26%), ST87 (10%), ST93 (6%), and ST461 and ST1516 (5% each). Several L. pneumophila STs were found to be limited to certain geographical regions. This is the first study to investigate the prevalence and diversity of Legionella in hotels and resorts in Israel during non-outbreak environmental inspections. These findings will inform risk assessment, surveillance, and control measures of TALD. Full article
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12 pages, 409 KiB  
Article
Prevention and Control of Legionella and Pseudomonas spp. Colonization in Dental Units
by Benedetta Tuvo, Michele Totaro, Maria Luisa Cristina, Anna Maria Spagnolo, David Di Cave, Sara Profeti, Angelo Baggiani, Gaetano Privitera and Beatrice Casini
Pathogens 2020, 9(4), 305; https://doi.org/10.3390/pathogens9040305 - 21 Apr 2020
Cited by 24 | Viewed by 3322
Abstract
Introduction: Dental Unit Waterlines (DUWLs) have shown to be a source of Legionella infection. We report the experience of different dental healthcare settings where a risk management plan was implemented. Materials and methods: In a Hospital Odontostomatology Clinic (HOC) and three Private Dental [...] Read more.
Introduction: Dental Unit Waterlines (DUWLs) have shown to be a source of Legionella infection. We report the experience of different dental healthcare settings where a risk management plan was implemented. Materials and methods: In a Hospital Odontostomatology Clinic (HOC) and three Private Dental Clinics (PDCs) housing 13 and six dental units (DUs), respectively, an assessment checklist was applied to evaluate staff compliance with guideline recommendations. DUWLs microbial parameters were investigated before and after the application of corrective actions. Results: In the HOC a poor adherence to good practices was demonstrated, whereas protocols were carefully applied in PDCs. L. pneumophila sg 2–15 was isolated in 31% (4/13) and 33% (2/6) of DUs in HOC and PDCs, respectively, mainly from handpieces (32%, 6/19) with counts >102 colony-forming units per milliliter (CFU/L), often associated with P. aeruginosa (68%, 13/19). The shock disinfection with 3% v/v hydrogen peroxide (HP) showed a limited effect, with a recolonization period of about 4 weeks. Legionella was eradicated only after 6% v/v HP shock disinfection and filters-installation, whilst P. aeruginosa after the third shock disinfection with a solution of 4% v/v HP and biodegradable surfactants. Conclusions: Our data demonstrate the presence and persistence of microbial contamination within the DUWLs, which required strict adherence to control measures and the choice of effective disinfectants. Full article
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23 pages, 487 KiB  
Review
Legionella pneumophila and Protozoan Hosts: Implications for the Control of Hospital and Potable Water Systems
by Muhammad Atif Nisar, Kirstin E. Ross, Melissa H. Brown, Richard Bentham and Harriet Whiley
Pathogens 2020, 9(4), 286; https://doi.org/10.3390/pathogens9040286 - 15 Apr 2020
Cited by 28 | Viewed by 3851
Abstract
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 [...] Read more.
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. Full article
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15 pages, 3498 KiB  
Article
Intracellular Behaviour of Three Legionella pneumophila Strains within Three Amoeba Strains, Including Willaertia magna C2c Maky
by Issam Hasni, Antoine Jarry, Benjamin Quelard, Antoine Carlino, Jean-Baptiste Eberst, Olivier Abbe and Sandrine Demanèche
Pathogens 2020, 9(2), 105; https://doi.org/10.3390/pathogens9020105 - 06 Feb 2020
Cited by 11 | Viewed by 3775
Abstract
Legionella pneumophila is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as Acanthamoeba castellanii. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species [...] Read more.
Legionella pneumophila is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as Acanthamoeba castellanii. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species support the growth of L. pneumophila. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to possess the ability to eliminate the L. pneumophila strain Paris. Here, we study the intracellular behaviour of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky and compare this strain to A. castellanii and W. magna Z503, which are used as controls. We observe the intracellular growth of strain Lens within W. magna Z503 and A. castellanii at 22 °C and 37 °C. Strain Paris grows within A. castellanii at any temperature, while it only grows at 22 °C within W. magna Z503. Strain Philadelphia proliferates only within A. castellanii at 37 °C. Within W. magna C2c Maky, none of the three legionella strains exhibit intracellular growth. Additionally, the ability of W. magna C2c Maky to decrease the number of internalized L. pneumophila is confirmed. These results support the idea that W. magna C2c Maky possesses unique behaviour in regard to L. pneumophila strains. Full article
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2019

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11 pages, 1253 KiB  
Article
Water Quality as a Predictor of Legionella Positivity of Building Water Systems
by David Pierre, Julianne L. Baron, Xiao Ma, Frank P. Sidari III, Marilyn M. Wagener and Janet E. Stout
Pathogens 2019, 8(4), 295; https://doi.org/10.3390/pathogens8040295 - 13 Dec 2019
Cited by 28 | Viewed by 4555
Abstract
Testing drinking water systems for the presence of Legionella colonization is a proactive approach to assess and reduce the risk of Legionnaires’ disease. Previous studies suggest that there may be a link between Legionella positivity in the hot water return line or certain [...] Read more.
Testing drinking water systems for the presence of Legionella colonization is a proactive approach to assess and reduce the risk of Legionnaires’ disease. Previous studies suggest that there may be a link between Legionella positivity in the hot water return line or certain water quality parameters (temperature, free chlorine residual, etc.) with distal site Legionella positivity. It has been suggested that these measurements could be used as a surrogate for testing for Legionella in building water systems. We evaluated the relationship between hot water return line Legionella positivity and other water quality parameters and Legionella colonization in premise plumbing systems by testing 269 samples from domestic cold and hot water samples in 28 buildings. The hot water return line Legionella positivity and distal site positivity only demonstrated a 77.8% concordance rate. Hot water return line Legionella positivity compared to distal site positivity had a sensitivity of 55% and a specificity of 96%. There was poor correlation and a low positive predictive value between the hot water return line and distal outlet positivity. There was no correlation between Legionella distal site positivity and total bacteria (heterotrophic plate count), pH, free chlorine, calcium, magnesium, zinc, manganese, copper, temperature, total organic carbon, or incoming cold-water chlorine concentration. These findings suggest that hot water return line Legionella positivity and other water quality parameters are not predictive of distal site positivity and should not be used alone to determine the building’s Legionella colonization rate and effectiveness of water management programs. Full article
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21 pages, 794 KiB  
Article
Advances in Legionella Control by a New Formulation of Hydrogen Peroxide and Silver Salts in a Hospital Hot Water Network
by Luna Girolamini, Ada Dormi, Tiziana Pellati, Paolo Somaroli, Davide Montanari, Andrea Costa, Francesca Savelli, Andrea Martelli, Antonella Grottola, Giulia Fregni Serpini and Sandra Cristino
Pathogens 2019, 8(4), 209; https://doi.org/10.3390/pathogens8040209 - 29 Oct 2019
Cited by 17 | Viewed by 3503
Abstract
Legionella surveillance is an important issue in public health, linked to the severity of disease and the difficulty associated with eradicating this bacterium from the water environment. Different treatments are suggested to reduce Legionella risk, however long-term studies of their efficiency are lacking. [...] Read more.
Legionella surveillance is an important issue in public health, linked to the severity of disease and the difficulty associated with eradicating this bacterium from the water environment. Different treatments are suggested to reduce Legionella risk, however long-term studies of their efficiency are lacking. This study focused on the activity of a new formulation of hydrogen peroxide and silver salts, WTP828, in the hospital hot water network (HWN) to contain Legionella contamination during two years of treatment. The effectiveness of WTP828 was tested measuring physical-chemical and microbiological parameters such as Legionella, Pseudomonas aeruginosa (P. aeruginosa), and a heterotopic plate count (HPC) at 36 °C. Legionella isolates were identified by serotyping and genotyping. WTP 828 induced a reduction in Legionella–positive sites (60% to 36%) and contamination levels (2.12 to 1.7 log10 CFU/L), with isolates belonging to L. pneumophila SG1 (ST1 and ST104), L. anisa and L. rubrilucens widely distributed in HWN. No relevant contamination was found for other parameters tested. The long-term effect of WTP828 on Legionella containment suggest the easy and safe application of this disinfectant, that combined with knowledge of building characteristics, an adequate environmental monitoring and risk assessment plan, become the key elements in preventing Legionella contamination and exposure. Full article
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