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Evaluation of Legionella spp. Colonization in Residential Buildings Having Solar Thermal System for Hot Water Production

Totaro M, Costa AL, Frendo L, Profeti S, Casini B, Gallo A, Privitera G, Baggiani A.

Department of Translational Research N.T.M.S, University of Pisa, Pisa, Italy.

Int J Environ Res Public Health 2020 Sep 26;17(19):7050.

Abstract: Despite an increase of literature data on Legionella spp. presence in private water systems, epidemiological reports assert a continuing high incidence of Legionnaires' disease infection in Italy. In this study, we report a survey on Legionella spp. colonization in 58 buildings with solar thermal systems for hot water production (TB). In all buildings, Legionella spp. presence was enumerated in hot and cold water samples. Microbiological potability standards of cold water were also evaluated. Legionella spp. was detected in 40% of the buildings. Moreover, we detected correlations between the count of Legionella spp. and the presence of the optimal temperature for the microorganism growth (less than 40 °C). Our results showed that cold water was free from microbiological hazards, but Legionella spp., was detected when the mean cold water temperature was 19.1 ± 2.2 °C. This may considered close to the suboptimal value for the Legionella growth (more than 20 °C). In conclusion, we observed the presence of a Legionnaires' disease risk and the need of some strategies aimed to reduce it, such as the application of training programs for all the workers involved in water systems maintenance.


Legionella Diversity and Spatiotemporal Variation in The Occurrence of Opportunistic Pathogens within a Large Building Water System

Buse HY, Morris BJ, Gomez-Alvarez V, Szabo JG, Hall JS.

US Environmental Protection Agency (USEPA), Cincinnati, OH, USA.

Pathogens 2020 Jul 13;9(7):567.

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 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.


The Role of Sensor-Activated Faucets in Surgical Handwashing Environment as a Reservoir of Legionella

Mazzotta M, Girolamini L, Pascale MR, Lizzadro J, Salaris S, Dormi A, Cristino S.

Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy.

Pathogens 2020 Jun 5;9(6):446.

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), 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.


Green waste compost as potential reservoirs of Legionella in the Netherlands

Huss A, Derks LAN, Heederik DJJ, Wouters IM.

Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.

Clin Microbiol Infect 2020 May 26:1259.e1-e1259.e3.

Abstract: Objectives: Legionella is a bacterial species able to cause influenza-like illness (Pontiac fever) or severe pneumonia (Legionnaires disease, LD). We assessed Legionella presence and concentration in composting facilities in The Netherlands. Methods: A total of 142 samples from 23 green waste composting facilities were screened for Legionella DNA using qPCR. Results: Of 142 samples, Legionella spp. DNA was detected in 97 (68%), and the subspecies L. pneumophila and L. longbeachae in 33 (23%) and one (0.7%) samples, respectively. Legionella was observed in samples from all composting facilities. The concentration of Legionella spp. DNA ranged from 103 to 105 genomic units (GU)/gram. Compost temperature was negatively correlated with the presence (odds ratio 0.67, 95% CI 0.50-0.92 per 10 degrees increase) and concentration (geometric mean ratio 0.90, 95% CI 0.83-0.97 per 10 degrees) of Legionella spp. Average humidity in the week prior to sampling was negatively correlated with the L. pneumophila concentration (geometric mean ratio 0.73, 95% CI 0.56-0.96 per increase in 10% of humidity). Discussion: This study suggests that composting facilities can be regarded as reservoirs of Legionella in The Netherlands, but additional studies should target if such facilities represent a human health risk.  



Legionella risk in evaporative cooling systems and underlying causes of associated breaches in health and safety compliance

Crook B, Willerton L, Smith D, Wilson L, Poran V, Helps J, McDermott P.

Health and Safety Executive, Buxton, SK17 9JN, UK.

Int J Hyg Environ Health 2020 Mar;224:113425.

Abstract: Legionella bacteria can colonise and proliferate in water systems in the built environment and can be spread by aerosol generation. If inhaled by a susceptible individual, this can lead to respiratory infections such as Legionnaires' Disease (LD), or the generally milder Pontiac fever. Evaporative cooling systems (ECS), including cooling towers, used in industrial processes to dissipate excessive heat are prone to contamination by Legionella. From these systems it is possible for contaminated aerosols to be dispersed over a wide area, potentially exposing workers on site, neighbouring workplaces or nearby members of the public. Analysis of reported data on outbreaks of LD in Great Britain, collated for a ten-year period, identified 44 separate legionellosis outbreaks of which seven were attributed to ECS and were responsible for 229 infections and 10 fatalities. This prompted an examination of health and safety inspection records which revealed, over a five-year period, 321 enforcement actions taken against failings in Legionella control, of which 31% were attributed to cooling towers. Based on this evidence, an intervention programme was undertaken by health and safety inspectors in which 1,906 sites with ECS were inspected. During these inspections, sites were rated against four topics that are used to demonstrate compliance with statutory requirements for Legionella control: Risk Assessment; Written Control Scheme; Implementation of Control Scheme; and Record Keeping. While there was compliance at the majority of sites, breaches of the legislation were found at 625 sites (33% of those inspected), leading to 409 Improvement Notices (compelling dutyholders to make improvements to health and safety breaches of law in a given timeframe) and 12 Prohibition Notices (compelling dutyholders to stop work until they have remedied breaches in health and safety law) being served at 229 sites (12.0% of those inspected). Data from the intervention programme was analysed to identify root causes of these breaches of legislation on Legionella control. The majority of Improvement Notices (53%) were issued for the 'lack of effective implementation of a Written Control Scheme', with 'Risk Assessment' and 'Written Control Scheme' both accounting for 23%. More detailed examination showed major problems to be lack of training; failure to maintain the cleanliness of cooling towers and the water within them; risk assessments either being absent or not up to date, i.e., no longer representing the risks present; and Written Control Schemes being absent or insufficiently detailed. This provides a valuable data resource for dutyholders, so that they can understand where they need to focus to achieve significant improvement in legal compliance and therefore reduce the risk of LD for employees and members of the public affected by their workplace, and valuable data for regulators to target future interventions aimed at improving dutyholder compliance leading to better protection of workers and members of the public.


Presence of Legionella Spp. In Cooling Towers: The Role of Microbial Diversity, Pseudomonas, and Continuous Chlorine Application

Paranjape K, Bédard É, Whyte LG, Ronholm J, Prévost M, Faucher SP.

Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada.

Water Res 2020 Feb;169:115252.

Abstract: Legionnaires' disease (LD) is a severe pneumonia caused by several species of the genus Legionella, most frequently by Legionella pneumophila. Cooling towers are the most common source for large community-associated outbreaks. Colonization, survival, and proliferation of L. pneumophila in cooling towers are necessary for outbreaks to occur. These steps are affected by the chemical and physical parameters of the cooling tower environment. We hypothesize that the bacterial community residing in the cooling tower could also affect the presence of L. pneumophila. A 16S rRNA gene targeted amplicon sequencing approach was used to study the bacterial community of cooling towers and its relationship with the Legionella spp. and L. pneumophila communities. The results indicated that the water source shaped the bacterial community of cooling towers. Several taxa were enriched and positively correlated with Legionella spp. and L. pneumophila. In contrast, Pseudomonas showed a strong negative correlation with Legionella spp. and several other genera. Most importantly, continuous chlorine application reduced microbial diversity and promoted the presence of Pseudomonas creating a non-permissive environment for Legionella spp. This suggests that disinfection strategies as well as the resident microbial population influences the ability of Legionella spp. to colonize cooling towers.


Dispersion of Legionella Bacteria in Atmosphere: A Practical Source Location Estimation Method

Dyke S, Barrass I, Pollock K, Hall IM.

School of Mathematics, The University of Manchester, Manchester, United Kingdom.

PLoS One 2019 Nov;14(11):e0224144.

Abstract: Legionnaires' disease, a form of pneumonia which can be fatal, is transmitted via the inhalation of water droplets containing Legionella bacteria. These droplets can be dispersed in the atmosphere several kilometers from their source. The most common such sources are contaminated water within cooling towers and other air-conditioning systems but other sources such as ornamental fountains and spa pools have also caused outbreaks of the disease in the past. There is an obvious need to locate and eliminate any such sources as quickly as possible. Here a maximum likelihood model estimating the source of an outbreak from case location data has been developed and implemented. Unlike previous models, the average dose exposure sub-model is formulated using a atmospheric dispersion model. How the uncertainty in inferred parameters can be estimated is discussed. The model is applied to the 2012 Edinburgh Legionnaires' disease outbreak.


Wide-scale Study of 206 Buildings in the Netherlands from 2011 to 2015 to Determine the Effect of Drinking Water Management Plans on the Presence of Legionella Spp

van der Lugt W, Euser SM, Bruin JP, den Boer JW, Yzerman EPF.

Van der Lugt B.V., Heiligland 28A, 1821, AC, Alkmaar, the Netherlands.

Water Res. 2019 Sep;161:581-589.

Abstract: Previous analysis of the Dutch National Legionella Outbreak Detection Program 2002-2012 has shown that buildings required to maintain a Legionella control plan for their drinking water installation are more likely to test positive for Legionella spp. Than buildings without such a plan (38% versus 22% of samples). To clarify this discrepancy, we analysed the results of mandatory water sample testing conducted as part of risk assessments in 206 buildings in the Netherlands from 2011 to 2015. Of the 6171 samples analysed, 16.2% exceeded the Dutch drinking water standard for Legionella spp. of 100 CFU/litre. In buildings with ≤50 tap points, the average percentage of samples containing ≥100 CFU/litre was 28.2%, and from buildings with >50 tap points, it was 12.2%. Analysis of serial samples (taken every 6 months) from each building showed that 33.2% of all buildings tested positive for at least one sample every 6 months. The overall increase was 4.4% per year. Analysis of Legionella subgroups showed that while the majority of positive samples contained L. non-pneumophila (96.9%), some samples did contain L. pneumophila serogroup 1 (1.0%) and serogroups 2-14 (2.1%). Our data suggest that the Dutch mandatory risk assessment and drinking water management plan is not sufficiently effective in preventing the proliferation of Legionella spp. and may even contribute to proliferation. This analysis should now be expanded to include other areas of the Netherlands in order to understand the geographical differences that we observed in our results, and why smaller buildings appear to be more likely to test positive for Legionella spp.


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

Valciņa O, Pūle D, Mališevs A, Trofimova J, Makarova S, Konvisers G, Bērziņš A, Krūmiņa A.

Institute of Food Safety, Animal Health and Environment "BIOR", LV-1076 Rīga, Latvia.

Medicina (Kaunas) 2019 Aug;55(8):492.

Abstract: 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.


Legionella pneumophila as a Health Hazard to Miners: A Pilot Study of Water Quality and QMRA

Madera-García V, Mraz AL, López-Gálvez N, Weir MH, Werner J, Beamer PI, Verhougstraete MP.

Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, AZ, USA.

Water (Basel) 2019 Aug;11(8):1528.

Abstract: Legionella pneumophila (L. pneumophila), the causative agent of legionellosis, is an aquatic bacterium that grows in warm water. Humans are only presented with a health risk when aerosolized water containing L. pneumophila is inhaled. In mining operations, aerosolized water is used as dust control and as part of the drilling operations, a currently ignored exposure route. This study characterized L. pneumophila concentrations in the mine's non-potable water and the relationship between L. pneumophila and chlorine concentrations. These concentrations informed a quantitative microbial risk assessment (QMRA) model to estimate the infection risk to miners exposed to aerosolized water containing L. pneumophila. Fourteen water samples were collected from seven locations at a mine and analyzed for temperature, pH, chlorine, and L. pneumophila serogroup. Most samples (93%) tested positive for L. pneumophila cells. The faucet from the sprinkler system on the adit level (entrance to the underground mine levels) showed the highest concentration of L. pneumophila (8.35×104 MPN/L). Disability adjusted life years (DALYs) were estimated in the QMRA model and showed that the risk for all miners was significantly lower (p<0.0001) with the ventilation system on than when the system was off. Our study showed that the use of a ventilation system at the adit level of the mine reduced the risk of infection with aerosolized L. pneumophila.


Attenuated Legionella pneumophila Survives for a Long Period in an Environmental Water Site

Nishida T, Nakagawa N, Watanabe K, Shimizu T, Watarai M.

The United Graduate School of Veterinary Science, Yamaguchi University, Japan.

Biomed Res Int 2019 Jul;2019:8601346.

Abstract: Legionella pneumophila is known as a human pathogen and is ubiquitous in natural and artificial aquatic environments. Many studies have revealed the virulence traits of L. pneumophila using clinical strains and a number of studies for characterizing environmental strains are also reported. However, the association between the virulence and survivability in the environment is unclear. In the present study, L. pneumophila was isolated from environmental water sites (Ashiyu foot spa, water fountain, and public bath), and the serogroups of isolated strains were determined by serological tests. Isolated strains were found to belong to serogroups SG1, SG2, SG3, SG4, SG5, SG8, SG9, and SG13. Untypeable strains were also obtained. Isolated strains were used for intracellular growth assay in a human monocytic cell line, THP-1. Among these strains, only an untypeable strain, named AY3, failed to replicate in THP-1. In addition, AY3 was maintained for a long period in an environmental water site, Ashiyu foot spa 2. Further, we compared the characteristics of several strains isolated from Ashiyu foot spa 2 and a clinical strain, Togus-1. AY3 failed to replicate in THP-1 cells but replicated in an amoeba model, Dictyostelium discoideum. Compared with Togus-1, the culturable cell number of environmental strains under stress conditions was higher. Moreover, biofilm formation was assessed, and AY3 showed the same degree of biofilm formation as Togus-1. Biofilm formation, replication in amoebae, and resistance against stress factors would explain the predominance of AY3 at one environmental site. Although the mechanism underlying the difference in the ability of AY3 to replicate in THP-1 cells or amoebae is still unclear, AY3 may abandon the ability to replicate in THP-1 cells to survive in one environment for a long period. Understanding the mechanisms of L. pneumophila in replication within different hosts should help in the control of Legionnaires' disease, but further study is necessary.


Quantitative Microbial Risk Assessment of Legionella pneumophila in a Drinking Water Supply System in Israel

Sharaby Y, Rodríguez-Martínez S, Höfle MG, Brettar I, Halpern M.

Department of Evolutionary and Environmental Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.

Sci Total Environ 2019 Jun;671:404-410.

Abstract: Legionella pneumophila cause human infections via inhalation of contaminated water aerosols, resulting in severe pneumonia. Legionella spp. prevalence was monitored in a drinking-water distribution system (DWDS) in Northern Israel. Five points (toilet faucets and showers) were sampled seasonally along a three years period. Toilet faucets and shower use, both generating aerosols, are known transmission routes for this pathogen and thus, present a potential health risk. Quantitative Microbial Risk Assessment (QMRA) was applied in order to assess the health risks posed by Legionella for these two exposure scenarios, while considering Legionella seasonality. The obtained results were compared with estimated tolerable risk levels of infection and of disease set by the USEPA and WHO. Both limits were expressed as Disability-Adjusted Life Years index (DALY) being 1×10-4 and 1×10-6, respectively. The QMRA revealed that the annual risk levels for both faucets and showers use exceeded the acceptable risk of infection with an average of 5.52×10-4 and 2.37×10-3 DALY'S per person per year, respectively. Annual risk levels were stable with no significant differences between the three years. Risk levels varied significantly between seasons by up to three orders of magnitude. Risk levels were highest during summer, autumn, and lowest during winter. The highest seasonal infection risk values were found in summer for both faucets and showers, which corresponded to 8.09×10-4 and 2.75×10-3 DALY'S per person per year, respectively. In conclusion, during summer and autumn there is a significant increase of the infection risk associated with exposure to Legionella-contaminated aerosols, in the studied water system. Public health assessment and prevention measures should focus on these seasons.


Legionella Growth Potential of Drinking Water Produced by a Reverse Osmosis Pilot Plant

Learbuch KLG, Lut MC, Liu G, Smidt H, van der Wielen PWJJ.

KWR Watercycle Research Institute, Nieuwegein, the Netherlands.

Water Res 2019 Jun;157:55-63.

Abstract: Treatment processes, such as membrane filtration with reverse osmosis (RO), are used to produce drinking water with a high degree of biostability. To our knowledge, the influence of RO water on biofilm formation and growth of L. pneumophila has not yet been investigated. Therefore, this study aimed (i) to determine the Legionella growth potential of (remineralised) RO-water produced by a pilot plant and to compare this to conventional treated groundwater, and (ii) to determine if different pipe materials, in contact with remineralised RO-water, can cause growth of L. pneumophila. The Legionella growth potential of water was determined with the boiler biofilm monitor (BBM) that mimics the flow of water in a premise plumbing system. The Legionella growth potential of materials in contact with remineralised RO-water was determined by using the biomass production potential (BPP)-test. ATP concentrations in the biofilm on the glass rings from the BBM fed with (remineralised) RO water fluctuated around 100 pg ATP cm-2. In contrast, BBMs fed with conventionally treated water resulted in ten-fold higher ATP concentrations in the biofilm. Moreover, conventionally treated water had a Legionella growth potential that was 1000-fold higher than that of (remineralised) RO-water. Furthermore, glass, copper and PVC-C had the lowest biofilm concentrations and Legionella growth potential in the BPP-test, followed by PE-Xb, PE-Xc and PE-100. The highest biofilm concentration and Legionella growth potential were with PVC-P. Hence, our study demonstrated that remineralised RO-water did not enhance growth of L. pneumophila in the BBM that mimics the premises plumbing system. However, when PE or PVC-P materials are used growth of L. pneumophila can still occur in the premises plumbing system despite the high quality of the supplied remineralised RO-water.


Legionella pneumophila Levels and Sequence-Type Distribution in Hospital Hot Water Samples from Faucets to Connecting Pipes

Bédard E, Paranjape K, Lalancette C, Villion M, Quach C, Laferrière C, Faucher SP, Prévost M.

Department of Civil Engineering, Polytechnique Montréal, Montréal, QC, Canada.

Water Res 2019 Jun;156:277-286.

Abstract: Recent studies have reported increased levels of Legionella pneumophila (Lp) at points of use compared to levels in primary and secondary components of hot water systems, suggesting possible selection by environmental conditions. In this study, concentrations of Lp in a hospital hot water system were evaluated by profile sampling, collecting successive water samples to determine the prevalence at the faucet (distal) and upstream piping before and after a system intervention to increase temperature. Lp strain diversity was compared between different points of use and different areas of the hot water system (i.e., tap, intermediate piping and main up flow piping). In total, 47 isolates were recovered from 32 positive hot water samples collected from designated taps, showers and recirculation loops; these isolates were subsequently analyzed by sequence-based typing (SBT). Lp levels were comparable between first draw (500 mL) and flushed (2 and 5 min) samples, whereas a decrease was observed in the amount of culturable cells (1 log). Two sequence types (STs) were identified throughout the system. ST378 (sg4/10) was present in 91% of samples, while ST154-like (sg1) was present in 41%; both STs were simultaneously recovered in 34% of samples. Isolated STs displayed comparable tolerance to copper (0.8-5 mg/L) and temperature (55°C, 1h) exposure. The ability to replicate within THP1 cells and Acanthamoeba castellanii was similar between the two STs and a comparative environmental outbreak strain. The low Lp diversity and the detection of both Lp sequence types in repeated subsequent samples collected from positive faucets in a hospital wing suggest a minimal impact of the distal conditions on strain selection for the sampled points, as well as a possible adaptation to stressors present in the system, leading to the predominance of a few strains.


Long-term Persistence of Infectious Legionella with Free-Living Amoebae in Drinking Water Biofilms

Shaheen M, Scott C, Ashbolt NJ.

School of Public Health, University of Alberta, Edmonton, Alberta, Canada.

Int J Hyg Environ Health 2019 May;222(4):678-686.

Abstract: Prolific growth of pathogenic Legionella pneumophila within engineered water systems and premise plumbing, and human exposure to aerosols containing this bacterium results in the leading health burden of any water-related pathogen in developed regions. Ecologically, free-living amoebae (FLA) are an important group of the microbial community that influence biofilm bacterial diversity in the piped-water environment. Using fluorescent microscopy, we studied in-situ the colonization of L. pneumophila in the presence of two water-related FLA species, Willaertia magna and Acanthamoeba polyphaga in drinking water biofilms. During water flow as well as after periods of long-stagnation, the attachment and colonization of L. pneumophila to predeveloped water-biofilm was limited. Furthermore, W. magna and A. polyphaga showed no immediate interactions with L. pneumophila when introduced to the same natural biofilm environment. A. polyphaga encysted within 5-7 d after introduction to the tap-water biofilms and mostly persisted in cysts till the end of the study period (850 d). W. magna trophozoites, however, exhibited a time delay in feeding on Legionella and were observed with internalized L. pneumophila cells after 3 weeks from their introduction to the end of the study period and supported putative (yet limited) intracellular growth. The culturable L. pneumophila in the bulk water was reduced by 2-log over 2 years at room temperature but increased (without a change in mip gene copies by qPCR) when the temperature was elevated to 40°C within the same closed-loop tap-water system without the addition of nutrients or fresh water. The overall results suggest that L. pneumophila maintains an ecological balance with FLA within the biofilm environment, and higher temperature improve the viability of L. pneumophila cells, and intracellular growth of Legionella is possibly cell-concentration dependent. Observing the preferential feeding behavior, we hypothesize that an initial increase of FLA numbers through feeding on a range of other available bacteria could lead to an enrichment of L. pneumophila, and later force predation of Legionella by the amoeba trophozoites results in rapid intracellular replication, leading to problematic concentration of L. pneumophila in water. In order to find sustainable control options for legionellae and various other saprozoic, amoeba-resisting bacterial pathogens, this work emphasizes the need for better understanding of the FLA feeding behavior and the range of ecological interactions impacting microbial population dynamics within engineered water systems.


The Sporadic Nature of Legionella pneumophila, Legionella pneumophila Sg1 and Mycobacterium Avium Occurrence Within Residences and Office Buildings Across 36 States in the United States

Donohue MJ, King D, Pfaller S, Mistry JH.

National Exposure Research Laboratory, United States Environmental Protection Agency, Cincinnati, OH, USA.

J Appl Microbiol 2019 May;126(5):1568-1579.

Abstract: Aim: Premise plumbing may disseminate the bacteria Legionella pneumophila and Mycobacterium avium, the causative agents for legionellosis and pulmonary nontuberculous mycobacterium disease respectively. Methods and results: Using quantitative PCR, the occurrence and persistence of L. pneumophila, L. pneumophila serogroup (Sg)1 and M. avium were evaluated in drinking water samples from 108 cold water taps (residences: n=43) and (office buildings: n=65). Mycobacterium avium, L. pneumophila and L. pneumophila Sg1 were detected 45, 41 and 25% of all structures respectively. Two occurrence patterns were evaluated: sporadic (a single detection from the three samplings) and persistent (detections in two or more of the three samples). Conclusions: The micro-organism's occurrence was largely sporadic. Office buildings were prone to microbial persistence independent of building age and square footage. Microbial persistence at residences was observed in those older than 40 years for L. pneumophila and was rarely observed for M. avium. The microbial occurrence was evenly distributed between structure types but there were differences in density and persistence. Significance of and impact of the study: The study is important because residences are often suspected to be the source when a case of disease is reported. These data demonstrate that this may not be the case for a sporadic incidence.


Occurrence of Legionella in Groundwater Used for Sprinkler Irrigation in Southern Italy

De Giglio O, Napoli C, Apollonio F, Brigida S, Marzella A, Diella G, Calia C, Scrascia M, Pacifico C, Pazzani C, Uricchio VF, Montagna MT.

Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.

Environ Res 2019 Mar;170:215-221.

Abstract: Legionellae are opportunistic bacteria that cause various conditions after exposure to contaminated aerosols, ranging from a serious type of pneumonia to a mild case of an influenza-like illness. Despite the risks of exposure, little is known about the occurrence of Legionella in natural environments and, even though studies have shown that there is a potential risk of transmission via inhalation, it does not have to be detected in groundwater that is used for irrigation. The culture methods traditionally used to detect Legionella have several limits that can be partly solved by applying molecular techniques. Samples from 177 wells in Apulia, Southern Italy, were collected twice, in winter and in summer, and analyzed. When compared with the guidelines, 145 (81.9%) of the sampled wells were suitable for irrigation use. The culture-based method highlighted the presence of different species and serogroups of Legionella in 31 (21.2%) of the 145 wells that were shown to be suitable for irrigation use. A greater number of wells returned positive results for Legionella in summer than in winter (p=0.023), and the median concentrations were mostly higher in summer (500 CFU/L) than in winter (300 CFU/L). The median temperature in the Legionella positive well waters was significantly higher than that in the negative ones, both in winter and in summer (p<0.001). Using molecular techniques, Legionella non-pneumophila was found in 37 of the 114 wells earlier detected as suitable for irrigation use but negative for Legionella by the culture-based methods. The distribution of Legionella differs significantly in porous aquifers compared to the karst-fissured ones both with quantitative polymerase chain reaction (qPCR) (p=0.0004) and viable cells by propidium monoazide (PMA-qPCR) (p=0.0000). Legionella concentrations were weakly correlated with temperature of water both with qPCR (ρ=0.47, p=0.0033) and PMA-qPCR (ρ=0.41, p=0.0126). Our data suggest that water that aerosolizes when sprinkled on plants represents a potential source of Legionellosis, with a higher risk from exposure in summer. On a practical level, this finding is important for workers (farmers and gardeners) who are in contact with waters used for irrigation.


Factors Influencing Legionella Contamination of Domestic Household Showers

Hayes-Phillips D, Bentham R, Ross K, Whiley H.

College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide 5001, Australia.

Pathogens 2019 Feb;8(1):27.

Abstract: Legionnaires' disease is a potentially fatal pneumonia like infection caused by inhalation or aspiration of water particles contaminated with pathogenic Legionella spp. Household showers have been identified as a potential source of sporadic, community-acquired Legionnaires' disease. This study used qPCR to enumerate Legionella spp. and Legionella pneumophila in water samples collected from domestic showers across metropolitan Adelaide, South Australia. A survey was used to identify risk factors associated with contamination and to examine awareness of Legionella control in the home. The hot water temperature was also measured. A total of 74.6% (50/68) and 64.2% (43/68) showers were positive for Legionella spp. and L. pneumophila, respectively.

Statistically significant associations were found between Legionella spp. concentration and maximum hot water temperature (p=0.000), frequency of shower use (p=0.000) and age of house (p=0.037). Lower Legionella spp. concentrations were associated with higher hot water temperatures, showers used at least every week and houses less than 5 years old. However, examination of risk factors associated with L. pneumophila found that there were no statistically significant associations (p>0.05) with L. pneumophila concentrations and temperature, type of hot water system, age of system, age of house or frequency of use. This study demonstrated that domestic showers were frequently colonized by Legionella spp. and L. pneumophila and should be considered a potential source of sporadic Legionnaires' disease. Increasing hot water temperature and running showers every week to enable water sitting in pipes to be replenished by the municipal water supply were identified as strategies to reduce the risk of Legionella in showers. The lack of public awareness in this study identified the need for public health campaigns to inform vulnerable populations of the steps they can take to reduce the risk of Legionella contamination and exposure.


Legionella Occurrence in Municipal and Industrial Wastewater Treatment Plants and Risks of Reclaimed Wastewater Reuse: Review

Caicedo C, Rosenwinkel KH, Exner M, Verstraete W, Suchenwirth R, Hartemann P, Nogueira R.

Leibniz University Hannover, Institute for Sanitary Engineering and Waste Management, Hannover, 30167, Germany. e

Water Res 2019 Feb;149:21-34.

Abstract: Wastewater treatment plants (WWTPs) have been identified as confirmed but until today underestimated sources of Legionella, playing an important role in local and community cases and outbreaks of Legionnaires' disease. In general, aerobic biological systems provide an optimum environment for the growth of Legionella due to high organic nitrogen and oxygen concentrations, ideal temperatures and the presence of protozoa. However, few studies have investigated the occurrence of Legionella in WWTPs, and many questions in regards to the interacting factors that promote the proliferation and persistence of Legionella in these treatment systems are still unanswered. This critical review summarizes the current knowledge about Legionella in municipal and industrial WWTPs, the conditions that might support their growth, as well as control strategies that have been applied. Furthermore, an overview of current quantification methods, guidelines and health risks associated with Legionella in reclaimed wastewater is also discussed in depth. A better understanding of the conditions promoting the occurrence of Legionella in WWTPs will contribute to the development of improved wastewater treatment technologies and/or innovative mitigation approaches to minimize future Legionella outbreaks.


Air-conditioner Cooling Towers as Complex Reservoirs and Continuous Source of Legionella pneumophila Infection Evidenced by a Genomic Analysis Study in 2017, Switzerland

Wüthrich D, Gautsch S, Spieler-Denz R, Dubuis O, Gaia V, Moran-Gilad J, Hinic V, Seth-Smith HM, Nickel CH, Tschudin-Sutter S, Bassetti S, Haenggi M, Brodmann P, Fuchs S, Egli A.

Division of Clinical Microbiology, University Hospital Basel, Basel, Switzerland.

Euro Surveill 2019 Jan;24(4):1800192.

Abstract: Introduction: Water supply and air-conditioner cooling towers (ACCT) are potential sources of Legionella pneumophila infection in people. During outbreaks, traditional typing methods cannot sufficiently segregate L. pneumophila strains to reliably trace back transmissions to these artificial water systems. Moreover, because multiple L. pneumophila strains may be present within these systems, methods to adequately distinguish strains are needed. Whole genome sequencing (WGS) and core genome multilocus sequence typing (cgMLST), with their higher resolution are helpful in this respect. In summer 2017, the health administration of the city of Basel detected an increase of L. pneumophila infections compared with previous months, signalling an outbreak. Aim: We aimed to identify L. pneumophila strains populating suspected environmental sources of the outbreak, and to assess the relations between these strains and clinical outbreak strains. Methods: An epidemiological and WGS-based microbiological investigation was performed, involving isolates from the local water supply and two ACCTs (n=60), clinical outbreak and non-outbreak related isolates from 2017 (n = 8) and historic isolates from 2003-2016 (n=26). Results: In both ACCTs, multiple strains were found. Phylogenetic analysis of the ACCT isolates showed a diversity of a few hundred allelic differences in cgMLST. Furthermore, two isolates from one ACCT showed no allelic differences to three clinical isolates from 2017. Five clinical isolates collected in the Basel area in the last decade were also identical in cgMLST to recent isolates from the two ACCTs. Conclusion: Current outbreak-related and historic isolates were linked to ACCTs, which form a complex environmental habitat where strains are conserved over years.


Prevalence of Infection-Competent Serogroup 6 Legionella pneumophila within Premise Plumbing in Southeast Michigan

Byrne BG, McColm S, McElmurry SP, Kilgore PE, Sobeck J, Sadler R, Love NG, Swanson MS.

Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA.

mBio. 2018;9(1):e00016-18.

Abstract: Coinciding with major changes to its municipal water system, Flint, MI, endured Legionnaires' disease outbreaks in 2014 and 2015. By sampling premise plumbing in Flint in the fall of 2016, we found that 12% of homes harbored legionellae, a frequency similar to that in residences in neighboring areas. To evaluate the genetic diversity of Legionella pneumophila in Southeast Michigan, we determined the sequence type (ST) and serogroup (SG) of the 18 residential isolates from Flint and Detroit, MI, and the 33 clinical isolates submitted by hospitals in three area counties in 2013 to 2016. Common to one environmental and four clinical samples were strains of L. pneumophila SG1 and ST1, the most prevalent ST worldwide. Among the Flint premise plumbing isolates, 14 of 16 strains were of ST367 and ST461, two closely related SG6 strain types isolated previously from patients and corresponding environmental samples. Each of the representative SG1 clinical strains and SG6 environmental isolates from Southeast Michigan infected and survived within macrophage cultures at least as well as a virulent laboratory strain, as judged by microscopy and by enumerating CFU. Likewise, 72 h after infection, the yield of viable-cell counts increased >100-fold for each of the representative SG1 clinical isolates, Flint premise plumbing SG6 ST367 and -461 isolates, and two Detroit residential isolates. We verified by immunostaining that SG1-specific antibody does not cross-react with the SG6 L. pneumophila environmental strains. Because the widely used urinary antigen diagnostic test does not readily detect non-SG1 L. pneumophila, Legionnaires' disease caused by SG6 L. pneumophila is likely underreported worldwide. IMPORTANCE: L. pneumophila is the leading cause of disease outbreaks associated with drinking water in the United States. Compared to what is known of the established risks of colonization within hospitals and hotels, relatively little is known about residential exposure to L. pneumophila One year after two outbreaks of Legionnaires' disease in Genesee County, MI, that coincided with damage to the Flint municipal water system, our multidisciplinary team launched an environmental surveillance and laboratory research campaign aimed at informing risk management strategies to provide safe public water supplies. The most prevalent L. pneumophila strains isolated from residential plumbing were closely related strains of SG6. In laboratory tests of virulence, the SG6 environmental isolates resembled SG1 clinical strains, yet they are not readily detected by the common diagnostic urinary antigen test, which is specific for SG1. Therefore, our study complements the existing epidemiological literature indicating that Legionnaires' disease due to non-SG1 strains is underreported around the globe.


Legionella Colonization of Hotel Water Systems in Touristic Places of Greece: Association with System Characteristics and Physicochemical Parameters

Kyritsi MA, Mouchtouri VA, Katsioulis A, Kostara E, Nakoulas V, Hatzinikou M, Hadjichristodoulou C.

Department of Hygiene and Epidemiology, Medical School, University of Thessaly, 41222 Larissa, Greece.

Int J Environ Res Public Health 2018 Nov;15(12):2707.

Abstract: This study aimed to assess the colonization of hotel water systems in central Greece and Corfu by Legionella, and to investigate the association between physicochemical parameters and Legionella colonization. Standardized hygiene inspection was conducted in 51 hotels, and 556 water samples were analyzed for Legionella spp. Free chlorine concentration, pH, hardness, conductivity, and trace metals were defined in cold water samples. The results of inspections and chemical analyses were associated with the microbiological results using univariate and logistic regression analysis. According to the score of the checklist used for the inspections, 17.6% of the hotels were classified as satisfactory, 15.7% as adequate, and 66.7% as unsatisfactory. Moreover, 74.5% of the hotels were colonized by Legionella spp. and 31.4% required remedial measures according to the European guidelines. Legionella spp. were isolated in 28% of the samples. Unsatisfactory results of inspections were associated with Legionella presence (relative risk (RR)=7.67, p-value=0.043). In hot-water systems, <50°C temperatures increased the risk of Legionella colonization (RR=5.36, p-value<0.001). In cold-water systems, free chlorine concentration <0.375 mg/L (odds ratio (OR)=9.76, p-value=0.001), pH ≥7.45 (OR=4.05, p-value=0.007), and hardness≥321 mgCaCO/L (OR=5.63, p-value=0.003) increased the risk, whereas copper pipes demonstrated a protective role (OR=0.29, p-value=0.0024). The majority of the hotels inspected were colonized with Legionella. Supplementary monitoring of the risk factors that were identified should be considered.


Prevalence of Legionella Species in Water Resources of Iran: A Systematic Review and Meta-Analysis

Khaledi A, Bahrami A, Nabizadeh E, Amini Y, Esmaeili D.

Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Teheran, Iran.

Iran J Med Sci 2018 Nov;43(6):571-580.

Abstract: Background: Legionella species are ubiquitous and naturally found in lakes, rivers, streams and hot springs, and other water resources. The present study aimed to investigate the prevalence of Legionella species in water resources of Iran by a systematic review and meta-analysis. Methods: In search of papers relevant to the prevalence of Legionella in water resources of Iran, the scientific information database in both English and Persian languages was used. The search was limited to studies between the year 2000 and end of July 2016. Each cohort and cross-sectional study that reported the contamination of water with Legionella was included in the present study. For data analysis, comprehensive meta-analysis software with Cochran's Q and I2 tests were used. P values less than 0.05 were considered statistically significant. Results: The prevalence of Legionella species in water resources of Iran was 27.3% (95% CI:25.3-29.3). The prevalence of Legionella spp. in hospital water, dental settings water, and other water resources were 28.8% (95% CI: 26.4-31.2), 23.6% (95% CI:16.1-33.2), and 29.6% (95% CI:25.6-33.8), respectively. The most common Legionella species was L. pneumophila with a prevalence of 60.5% (95% CI:53.3-67.2) and the prevalence of all other species was 52.5% (95% CI:44.7-60.2). The highest prevalence was reported in Isfahan with 55.7% (95% CI:48.0-63.0).

Conclusion: Based on the results, the prevalence rate of Legionella species in water resources of Iran was high and the most common Legionella species was L. pneumophila.


Spatial Structuring of a Legionella pneumophila Population Within the Water System of a Large Occupational Building

David S, Mentasti M, Lai S, Vaghji L, Ready D, Chalker VJ, Parkhill J.

Pathogen Genomics, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK.

Respiratory and Vaccine Preventable Bacteria Reference Unit, Public Health England, Colindale, London, UK.

Microb Genom 2018 Oct;4(10):e000226.

Abstract: The diversity of Legionella pneumophila populations within single water systems is not well understood, particularly in those unassociated with cases of Legionnaires' disease. Here, we performed genomic analysis of 235 L. pneumophila isolates obtained from 28 water samples in 13 locations within a large occupational building. Despite regular treatment, the water system of this building is thought to have been colonized by L. pneumophila for at least 30 years without evidence of association with Legionnaires' disease cases. All isolates belonged to one of three sequence types (STs), ST27 (n=81), ST68 (n=122) and ST87 (n=32), all three of which have been recovered from Legionnaires' disease patients previously. Pairwise single nucleotide polymorphism differences amongst isolates of the same ST were low, ranging from 0 to 19 in ST27, from 0 to 30 in ST68 and from 0 to 7 in ST87, and no homologous recombination was observed in any lineage. However, there was evidence of horizontal transfer of a plasmid, which was found in all ST87 isolates and only one ST68 isolate. A single ST was found in 10/13 sampled locations, and isolates of each ST were also more similar to those from the same location compared with those from different locations, demonstrating spatial structuring of the population within the water system. These findings provide the first insights into the diversity and genomic evolution of a L. pneumophila population within a complex water system not associated with disease.


Conventional Wastewater Treatment and Reuse Site Practices Modify Bacterial Community Structure but Do Not Eliminate Some Opportunistic Pathogens in Reclaimed Water

Kulkarni P, Olson ND, Paulson JN, Pop M, Maddox C, Claye E, Rosenberg Goldstein RE, Sharma M, Gibbs SG, Mongodin EF, Sapkota AR.

Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, MD, USA.

Sci Total Environ 2018 Oct;639:1126-1137.

Abstract: Water recycling continues to expand across the United States, from areas that have access to advanced, potable-level treated reclaimed water, to those having access only to reclaimed water treated at conventional municipal wastewater treatment plants. This expansion makes it important to further characterize the microbial quality of these conventionally treated water sources. Therefore, we used 16S rRNA gene sequencing to characterize total bacterial communities present in differentially treated wastewater and reclaimed water (n=67 samples) from four U.S. wastewater treatment plants and one associated spray irrigation site conducting on-site ultraviolet treatment and open-air storage. The number of observed operational taxonomic units was significantly lower (p<0.01) in effluent, compared to influent, after conventional treatment. Effluent community structure was influenced more by treatment method than by influent community structure. The abundance of Legionella spp. increased as treatment progressed in one treatment plant that performed chlorination and in another that seasonally chlorinated. Overall, the alpha-diversity of bacterial communities in reclaimed water decreased (p<0.01) during wastewater treatment and spray irrigation site ultraviolet treatment (p<0.01), but increased (p<0.01) after open-air storage at the spray irrigation site. The abundance of Legionella spp. was higher at the sprinkler system pumphouse at the spray irrigation site than in the influent from the treatment plant supplying the site. Legionella pneumophila was detected in conventionally treated effluent samples and in samples collected after ultraviolet treatment at the spray irrigation site, while Legionella feeleii persisted throughout on-site treatment at the spray irrigation site, and, along with Mycobacterium gordonae, was also detected at the sprinkler system pumphouse at the spray irrigation site. These data could inform the development of future treatment technologies and reuse guidelines that address a broader assemblage of the bacterial community of reclaimed water, resulting in reuse practices that may be more protective of public health.


The Presence and Prevalence of Legionella Spp in Collected Rainwater and Its Aerosolisation During Common Gardening Activities

Steege L, Moore G.

Biosafety, Air and Water Microbiology Group, National Infection Service, Public Health England, Porton Down, Salisbury SP4 0JG, UK.

Perspect Public Health 2018 Sep;138(5):254-260.

Abstract: Aims: To determine the presence and prevalence of Legionella spp in domestic rainwater storage butts and to quantify its aerosolisation when collected rainwater is used for common gardening activities. Methods: Volunteers were asked to take a water sample from their garden rainwater storage butt. The presence of Legionella was determined using quantitative polymerase chain reaction (qPCR). Two new rainwater storage butts were installed on-site at PHE Porton and positioned in sunlight or in the shade. Ambient conditions and those within the two 'experimental' water butts were continually monitored. A cyclone air sampler was used to detect the presence of Legionella in the air when collected rainwater was poured from a watering can or delivered via a hosepipe attached to a submersible water butt pump. Results: A total of 63 volunteers provided water samples from 113 different rainwater storage butts. Legionella spp was detected in 107 of these samples at a mean concentration of 4.7×104 genomic units l-1. Two of these samples also contained L. pneumophila. The water butt positioned in the shade stored water at a significantly lower temperature than that exposed to sunlight. While the concentration of Legionella was significantly higher in this cooler water, meteorological conditions rather than conditions within the water butt had the greatest effect upon Legionella concentration. No Legionella was detected in the air when rainwater was poured from a watering can. However, using a hose pipe on a 'fine spray' setting increased both the number of organisms detected in the air and their dissemination. Conclusion: In this study, Legionella spp were common contaminants of collected rainwater. However, the use of rainwater for common gardening activities should not be discouraged. Aerosolisation of Legionella when using a watering can is minimal and any increased risk associated with hose pipe use can be mitigated by using a coarse spray setting.


Risk of Infection from Legionella Associated with Spray Irrigation of Reclaimed Water

Pepper IL, Gerba CP.

Department of Soil, Water and Environmental Science, University of Arizona, 2959 W. Calle Agua Nueva, Tucson, AZ, 85745, USA.

Water Res 2018 Aug;139:101-107.

Abstract: Legionella pneumophila has been detected in reclaimed water used for spray irrigation of turfgrass in public parks and golf courses. This study determined the risks of infection from exposure to various levels of Legionella in reclaimed waters considering: the method of spray application; and the duration and frequency of exposure. Evaluation of these factors resulted in a risk of infection greater than 1:10,000 for several scenarios when the number of Legionella in the reclaimed water exceeded 1000 colony-forming units (CFU) per ml. Most current guidelines for control of Legionella in distribution systems recommend that increased monitoring or remedial action be taken when Legionella levels exceed 1000 to 10,000 CFU/ml. Based upon our risk assessment, these guidelines seem appropriate for reclaimed water systems where spray irrigation is practiced.


Legionella pneumophila Contamination of Hospital Dishwashers

Yoshida M, Furuya N, Hosokawa N, Kanamori H, Kaku M, Koide M, Higa F, Fujita J.

Department of Infection Control and Laboratory Diagnostics, Tohoku University Graduate School of Medicine, Sendai, Japan.

Am J Infect Control 2018 Aug;46(8):943-945.

Abstract: In a tertiary hospital, Legionella spp were isolated from taps and from ward dishwashers connected to contaminated tap piping. Our investigation revealed favorable conditions for growth of Legionella and showed that Legionella pneumophila SG6 isolates from the taps and dishwashers were all genetically identical by repetitive-element polymerase chain reaction. These results suggest that contaminated dishwashers might be a potential reservoir for the spread of Legionella in health care facilities.


Data on Legionella Prevalence and Water Quality in Showers of Retirement Homes and Group Homes in the Province of Rome, Lazio Region, Italy

De Filippis P, Mozzetti C, Messina A, D'Alò GL.

Section of Hygiene, Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy.

Data Brief 2018 Jul;19:2364-2373.

Abstract: The data presented in this article are related to the research paper titled "Prevalence of Legionella in retirement homes and group homes water distribution systems" (De Filippis, 2018) [3]. Most of the cases of Legionella infection are sporadic and occur in community-dwellers. Hot water and biofilm samples from the showerheads of 26 retirement homes and 9 group homes hosting closed communities were collected, in order to evaluate the prevalence of Legionella and generic water quality parameters (Heterotrophic Plate Counts at 22°C and 37°C). Samples were tested by culture method for the presence of Legionella. Confirmation and identification were carried out through Latex test and PCR. Further data about buildings' number of floors and rooms were collected and put in relation to the presence of Legionella through constructing contingency tables and performing exact fisher׳s or Chi-square tests. Cold (<30°C) water samples are analyzed apart.


Microbial Ecology and Water Chemistry Impact Regrowth of Opportunistic Pathogens in Full-Scale Reclaimed Water Distribution Systems

Garner E, McLain J, Bowers J, Engelthaler DM, Edwards MA, Pruden A.

Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA.

Environ Sci Technol 2018 Jul;52(16):9056-9068.

Abstract: Need for global water security has spurred growing interest in wastewater reuse to offset demand for municipal water. While reclaimed (i.e., non-potable) microbial water quality regulations target fecal indicator bacteria, opportunistic pathogens (OPs), which are subject to regrowth in distribution systems and spread via aerosol inhalation and other non-ingestion routes, may be more relevant. This study compares the occurrences of five OP gene markers (Acanthamoeba spp., Legionella spp., Mycobacterium spp., Naegleria fowleri, Pseudomonas aeruginosa) in reclaimed versus potable water distribution systems and characterizes factors potentially contributing to their regrowth. Samples were collected over four sampling events at the point of compliance for water exiting treatment plants and at five points of use at four U.S. utilities bearing both reclaimed and potable water distribution systems. Reclaimed water systems harbored unique water chemistry (e.g., elevated nutrients), microbial community composition, and OP occurrence patterns compared to potable systems examined here and reported in the literature. Legionella spp. genes, Mycobacterium spp. genes, and total bacteria, represented by 16S rRNA genes, were more abundant in reclaimed than potable water distribution system samples (p≤0.0001). This work suggests that further consideration should be given to managing reclaimed water distribution systems with respect to non-potable exposures to OPs.


The Growing Impact of Legionella in the Flint Water Crisis

Craft-Blacksheare M.

University of Michigan-Flint School of Nursing, Flint, MI, USA.

J Natl Black Nurses Assoc 2018 Jul;29(1):44-50.

Abstract: The water crisis in Flint, Michigan raised national awareness about lead- tainted drinking water, particularly its harm to children and pregnant and lactating women. However, according to recent findings, there may be another by-product of this man-made crisis. Failure to use anticorrosive material in the water, a practice mandated by the 1978 Clean Water Act, is being linked to an outbreak of Legionnaires' disease, an illness detrimental primarily to adults over 65 years of age. While Legionnaires' disease is relatively rare, it is also likely to remain undiagnosed. Clinicians, therefore, are urged to consider this diagnosis in adults with pneumonia that does not respond to typical antibiotic treatment, and in newborns with respiratory distress along with other non-typical symptoms as well as those who have had water births or who were exposed to ultrasonic, cool-mist humidification.


Health Risks from Exposure to Legionella in Reclaimed Water Aerosols: Toilet Flushing, Spray Irrigation, and Cooling Towers

Hamilton KA, Hamilton MT, Johnson W, Jjemba P, Bukhari Z, LeChevallier M, Haas CN.

Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.

Water Res 2018 May;34:261-279.

Abstract: The use of reclaimed water brings new challenges for the water industry in terms of maintaining water quality while increasing sustainability. Increased attention has been devoted to opportunistic pathogens, especially Legionella pneumophila, due to its growing importance as a portion of the waterborne disease burden in the United States. Infection occurs when a person inhales a mist containing Legionella bacteria. The top three uses for reclaimed water (cooling towers, spray irrigation, and toilet flushing) that generate aerosols were evaluated for Legionella health risks in reclaimed water using quantitative microbial risk assessment (QMRA). Risks are compared using data from nineteen United States reclaimed water utilities measured with culture-based methods, quantitative PCR (qPCR), and ethidium-monoazide-qPCR. Median toilet flushing annual infection risks exceeded 10-4 considering multiple toilet types, while median clinical severity infection risks did not exceed this value. Sprinkler and cooling tower risks varied depending on meteorological conditions and operational characteristics such as drift eliminator performance. However, the greatest differences between risk scenarios were due to 1) the dose response model used (infection or clinical severity infection) 2) population at risk considered (residential or occupational) and 3) differences in laboratory analytical method. Theoretical setback distances necessary to achieve a median annual infection risk level of 10-4 are proposed for spray irrigation and cooling towers. In both cooling tower and sprinkler cases, Legionella infection risks were non-trivial at potentially large setback distances and indicate other simultaneous management practices could be needed to manage risks. The sensitivity analysis indicated that the most influential factors for variability in risks were the concentration of Legionella and aerosol partitioning and/or efficiency across all models, highlighting the importance of strategies to manage Legionella occurrence in reclaimed water.


Rapid Identification of a Cooling Tower-Associated Legionnaires' Disease Outbreak Supported by Polymerase Chain Reaction Testing of Environmental Samples, New York City, 2014-2015

Benowitz I, Fitzhenry R, Boyd C, Dickinson M, Levy M, Lin Y, Nazarian E, Ostrowsky B, Passaretti T, Rakeman J, Saylors A, Shamoonian E, Smith TA, Balter S.

Division of Healthcare Quality Promotion, CDC, Atlanta, Georgia, USA.

J Environ Health 2018 Apr;80(8):8-12.

Abstract: We investigated an outbreak of eight Legionnaires' disease cases among persons living in an urban residential community of 60,000 people. Possible environmental sources included two active cooling towers (air-conditioning units for large buildings) <1 km from patient residences, a market misting system, a community-wide water system used for heating and cooling, and potable water. To support a timely public health response, we used real-time polymerase chain reaction (PCR) to identify Legionella DNA in environmental samples within hours of specimen collection. We detected L. pneumophila serogroup 1 DNA only at a power plant cooling tower, supporting the decision to order remediation before culture results were available. An isolate from a power plant cooling tower sample was indistinguishable from a patient isolate by pulsed-field gel electrophoresis, suggesting the cooling tower was the outbreak source. PCR results were available <1 day after sample collection, and culture results were available as early as 5 days after plating. PCR is a valuable tool for identifying Legionella DNA in environmental samples in outbreak settings.


Legionella Spp. Risk Assessment in Recreational and Garden Areas of Hotels

Papadakis A, Chochlakis D, Sandalakis V, Keramarou M, Tselentis Y, Psaroulaki A.

Department of Clinical Microbiology and Microbial Pathogenesis, School of Medicine, University of Crete, Crete, Greece.

Int J Environ Res Public Health 2018 Mar;15(4):598.

Abstract: Several Travel-associated Legionnaires' disease (TALD) cases occur annually in Europe. Except from the most obvious sites (cooling towers and hot water systems), infections can also be associated with recreational, water feature, and garden areas of hotels. This argument is of great interest to better comprehend the colonization and to calculate the risk to human health of these sites. From July 2000-November 2017, the public health authorities of the Island of Crete (Greece) inspected 119 hotels associated with TALD, as reported through the European Legionnaires' Disease Surveillance Network. Five hundred and eighteen samples were collected from decorative fountain ponds, showers near pools and spas, swimming pools, spa pools, garden sprinklers, drip irrigation systems (reclaimed water) and soil. Of those, 67 (12.93%), originating from 43 (35.83%) hotels, tested positive for Legionella (Legionella pneumophila serogroups 1, 2, 3, 6, 7, 8, 13, 14, 15 and non-pneumophila species (L. anisaL. erythraL. taurinensisL. birminghamensisL. rubrilucens). A Relative Risk (R.R.)>1 (p<0.0001) was calculated for chlorine concentrations of less than 0.2 mg/L (R.R.: 54.78), star classification (<4) (R.R.:4.75) and absence of Water Safety Plan implementation (R.R.:3.96). High risk (≥10⁴ CFU/L) was estimated for pool showers (16.42%), garden sprinklers (7.46%) and pool water (5.97%).


Colonization of Legionella Spp. In Dental Unit Waterlines

Carinci F, Scapoli L, Contaldo M, Santoro R, Palmieri A, Pezzetti F, Lauritano D, Candotto V, Mucchi D, Baggi L, Tagliabue A, Tettamanti L.

Department of Medicine and Surgery, University of Insubria, Varese, Italy.

J Biol Regul Homeost Agents 2018 Jan-Feb;32(2 Suppl. 1):139-142.

Abstract: Legionella spp. are ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines. Surveys have shown that the percentage of samples taken at different dental sites that were positive for Legionella spp. were highly variable and ranged from 0% to 100%. Cultivation is the principal approach to evaluating bacterial contamination employed in the past but applying this approach to testing for Legionella spp. may result in false-negative data or underestimated bacterial counts. PCR and direct fluorescent counts can detect viable non-cultivable bacteria, which are not counted by plating procedures. Legionella spp. commonly form such viable non-culturable cells and it is likely that they contribute to the difference between plate count results and those of PCR and fluorescent-antibody detection. However, studies have shown that Legionella is present in the municipal water source in spite of the current filtration and chlorination procedures. Once Legionella reaches the building water system, it settles down into a biofilm layer of stagnant water. By means of this layer, Legionella can protect itself from antimicrobial agents and then multiply. Dental unit waterlines may be contaminated with opportunistic bacteria. The water quality in the dental units should be controlled to eliminate opportunistic pathogens and to provide water for dental treatment that meets public health standards for potable water.


A Review of Roof Harvested Rainwater in Australia

Chubaka CE, Whiley H, Edwards JW, Ross KE.

Environmental Health, Science and Engineering, Flinders University, Adelaide, Australia.

J Environ Public Health 2018 Jan;2018:6471324.

Abstract: To address concern regarding water sustainability, the Australian Federal Government and many state governments have implemented regulatory mechanisms and incentives to support households to purchase and install rainwater harvesting systems. This has led to an increase in rainwater harvesting in regional and urban Australia. This review examines the implementation of the regulatory mechanisms across Australia. In addition, the literature investigating the potential health consequences of rainwater consumption in Australia was explored. Studies demonstrated that although trace metals such as arsenic, cadmium, chromium, lead, and iron were present in Australian rainwater, these metallic elements were generally found below the health limit guideline, except in high industrial areas. In addition, pathogenic or indicator microorganisms that include, but are not limited to, Escherichia coli, total and faecal coliforms, CampylobacterSalmonellaLegionellaPseudomonasCryptosporidium, Enterococci, GiardiaAeromonas, and Mycobacterium avium Complex (MAC) have been detected in rainwater collected in Australia. However, epidemiological evidence suggests that drinking rainwater does not increase the risk of gastrointestinal disease. It was also identified that there is a need for further research investigating the potential for rainwater to be a source of infection for opportunistic pathogens.


Distribution of Legionella and Bacterial Community Composition Among Regionally Diverse US Cooling Towers

Llewellyn AC, Lucas CE, Roberts SE, Brown EW, Nayak BS, Raphael BH, Winchell JM.

Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, CDC, Atlanta, GA, USA.

PLoS One 2017 Dec;12(12):e0189937.

Abstract: Cooling towers (CTs) are a leading source of outbreaks of Legionnaires' disease (LD), a severe form of pneumonia caused by inhalation of aerosols containing Legionella bacteria. Accordingly, proper maintenance of CTs is vital for the prevention of LD. The aim of this study was to determine the distribution of Legionella in a subset of regionally diverse US CTs and characterize the associated microbial communities. Between July and September of 2016, we obtained aliquots from water samples collected for routine Legionella testing from 196 CTs located in eight of the nine continental US climate regions. After screening for Legionella by PCR, positive samples were cultured and the resulting Legionella isolates were further characterized. Overall, 84% (164) were PCR-positive, including samples from every region studied. Of the PCR-positive samples, Legionella spp were isolated from 47% (78), L. pneumophila was isolated from 32% (53), and L. pneumophila serogroup 1 (Lp1) was isolated from 24% (40). Overall, 144 unique Legionella isolates were identified; 53% (76) of these were Legionella pneumophila. Of the 76 L. pneumophila isolates, 51% (39) were Lp1. Legionella were isolated from CTs in seven of the eight US regions examined. 16S rRNA amplicon sequencing was used to compare the bacterial communities of CT waters with and without detectable Legionella as well as the microbiomes of waters from different climate regions. Interestingly, the microbial communities were homogenous across climate regions. When a subset of seven CTs sampled in April and July were compared, there was no association with changes in corresponding CT microbiomes over time in the samples that became culture-positive for Legionella. Legionella species and Lp1 were detected frequently among the samples examined in this first large-scale study of Legionella in US CTs. Our findings highlight that, under the right conditions, there is the potential for CT-related LD outbreaks to occur throughout the US.



Risk Assessment of Colonization of Legionella Spp. In Dental Unit Waterlines

Lauritano D, Nardone M, Gaudio RM, Candotto V, Carinci F.

Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy.

Oral Implantol (Rome) 2017 Nov;10(3):283-288.

Abstract: The aerosol produced during the use of dental instruments can spread pathogens potentially harmful to health. Most of the pathogens found in hydraulic system are Gram-negative aerobic heterotrophic environmental bacterial species exhibiting very low pathogenicity, although they may be of concern in the treatment of vulnerable patients, such as immunocompromised, medically compromised individuals and dental team. Dental team can be exposed to pathogenic microorganisms including cytomegalovirus, hepatitis B virus, hepatitis C virus, herpes simplex virus and Legionella spp. Legionella spp. are ubiquitous in hydraulic system, in fact surveys have shown that the percentage of samples taken at different dental chairs that were positive for Legionella spp. and ranged from 0 to 100%. The concentration of Legionella spp. in hydraulic system may reach 1000 organisms per ml. The primary route of Legionella spp. transmission is inhalation or aspiration of environmentally contaminated aerosols. All dentists are required to conduct a statutory risk assessment of their hydraulic system, in fact to comply with their legal duties, dentists must identify and assess the sources of risk and prepare a scheme for preventing and controlling risks. Moreover, they must monitor the quality of their hydraulic system at least annually to ensure that they are "legionellae free".


Ten Questions Concerning the Aerosolization and Transmission of Legionella in the Built Environment

Prussin AJ 2nd, Schwake DO, Marr LC.

Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA.

Build Environ 2017 Oct;123:684-695.

Abstract: Legionella is a genus of pathogenic Gram-negative bacteria responsible for a serious disease known as legionellosis, which is transmitted via inhalation of this pathogen in aerosol form. There are two forms of legionellosis: Legionnaires' disease, which causes pneumonia-like symptoms, and Pontiac fever, which causes influenza-like symptoms. Legionella can be aerosolized from various water sources in the built environment including showers, faucets, hot tubs/swimming pools, cooling towers, and fountains. Incidence of the disease is higher in the summertime, possibly because of increased use of cooling towers for air conditioning systems and differences in water chemistry when outdoor temperatures are higher. Although there have been decades of research related to Legionella transmission, many knowledge gaps remain. While conventional wisdom suggests that showering is an important source of exposure in buildings, existing measurements do not provide strong support for this idea. There has been limited research on the potential for Legionella transmission through heating, ventilation, and air conditioning (HVAC) systems. Epidemiological data suggest a large proportion of legionellosis cases go unreported, as most people who are infected do not seek medical attention. Additionally, controlled laboratory studies examining water-to-air transfer and source tracking are still needed. Herein, we discuss ten questions that spotlight current knowledge about Legionella transmission in the built environment, engineering controls that might prevent future disease outbreaks, and future research that is needed to advance understanding of transmission and control of legionellosis.


Human Health Risks for Legionella and Mycobacterium Avium Complex (MAC) from Potable and Non-Potable Uses of Roof-Harvested Rainwater

Hamilton KA, Ahmed W, Toze S, Haas CN.

Drexel University, Philadelphia, PA, USA.

Water Res 2017 Aug;119:288-303.

Abstract: A quantitative microbial risk assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP) and Mycobacterium avium complex (MAC) was undertaken for various uses of roof-harvested rainwater (RHRW) reported in Queensland, Australia to identify appropriate usages and guide risk management practices. Risks from inhalation of aerosols due to showering, swimming in pools topped up with RHRW, use of a garden hose, car washing, and toilet flushing with RHRW were considered for LP while both ingestion (drinking, produce consumption, and accidental ingestion from various activities) and inhalation risks were considered for MAC. The drinking water route of exposure presented the greatest risks due to cervical lymphadenitis and disseminated infection health endpoints for children and immune-compromised populations, respectively. It is therefore not recommended that these populations consume untreated rainwater. LP risks were up to 6 orders of magnitude higher than MAC risks for the inhalation route of exposure for all scenarios. Both inhalation and ingestion QMRA simulations support that while drinking, showering, and garden hosing with RHRW may present the highest risks, car washing and clothes washing could constitute appropriate uses of RHRW for all populations, and toilet flushing and consumption of lettuce irrigation with RHRW would be appropriate for non- immune-compromised populations.


A Discussion About Public Health, Lead and Legionella pneumophila in Drinking Water Supplies in the United States

Rosen MB, Pokhrel LR, Weir MH.

Division of Environmental Health, Department of Epidemiology and Biostatistics, College of Public Health, Temple University, Philadelphia, USA.

Sci Total Environ 2017 Jul;590-591:843-852. 

Abstract: Lead (Pb) in public drinking water supplies has garnered much attention since the outset of the Flint water crisis. Pb is a known hazard in multiple environmental matrices, exposure from which results in long-term deleterious health effects in humans. This discussion paper aims to provide a succinct account of environmental Pb exposures with a focus on water Pb levels (WLLs) in the United States. It is understood that there is a strong correlation between WLLs and blood Pb levels (BLLs), and the associated health effects. However, within the Flint water crisis, more than water chemistry and Pb exposure occurred. A cascade of regulatory and bureaucratic failures culminated in the Flint water crisis. This paper will discuss pertinent regulations and responses including their limitations after an overview of the public health effects from Pb exposure as well as discussion on our limitations on monitoring and mitigating Pb in tap water. As the Flint water crisis also included increased Legionnaires' disease, caused by Legionella pneumophila, this paper will discuss factors influencing L. pneumophila growth. This will highlight the systemic nature of changes to water chemistry and public health impacts. As we critically analyze these important aspects of water research, we offer discussions to stimulate future water quality research from a new and systemic perspective to inform and guide public health decision-making.


Occurrence of Legionella in Showers at Recreational Facilities

De Filippis P, Mozzetti C, Amicosante M, D'Alò GL, Messina A, Varrenti D, Giammattei R, Di Giorgio F, Corradi S, D'Auria A, Fraietta R, Gabrieli R.

Section of Hygiene, Department of Biomedicine and Prevention, University of Rome 'Tor Vergata', Rome, Italia.

J Water Health 2017 Jun;15(3):402-409.

Abstract: Critical environments, including water systems in recreational settings, represent an important source of Legionella pneumophila infection in humans. In order to assess the potential risk for legionellosis, we analyzed Legionella contamination of water distribution systems in 36 recreational facilities equipped with swimming pools. One hundred and sixty water samples were analyzed from shower heads or taps located in locker rooms or in bathrooms. By culture method and polymerase chain reaction, 41/160 samples were positive for Legionella from 12/36 recreational centers. Hotels (57.1%) and sports centers (41.2%) were the most contaminated. L. pneumophila serotypes 2-14 (25/41) were more frequently found than serotype 1 (10/41). Samples at temperature ≥30°C were more frequently positive than samples at temperature <30°C (n=39 vs n=2, p<0.00001). The presence of L. pneumophila was investigated by comparison with heterotrophic plate count (HPC), an indicator of water quality. The presence of L. pneumophila was associated more frequently with high and intermediate HPC load at 37°C, therefore should be considered a potential source when HPC at 37°C is >10 CFU/mL. Maintenance, good hygiene practices, interventions on the hydraulic system and regular controls must be implemented to minimize exposure to L. pneumophila infection risk.


Legionella Spp. In Dental Unit Waterlines

Sedlata Juraskova E, Sedlackova H, Janska J, Holy O, Lalova I, Matouskova I.

Institute of Dentistry and Oral Sciences, Faculty of Medicine and Dentistry, Palacky University Olomouc and University Hospital Olomouc, Czech Republic.

Bratisl Lek Listy 2017 May;118(5):310-314.

Abstract: Objective: To determine the current presence of Legionella spp. in the output water of dental unit waterlines (DUWLs) and examine its mitigation by disinfection at the Institute of Dentistry and Oral Sciences, Faculty of Medicine and Dentistry, Palacky University Olomouc and University Hospital Olomouc. Material and methods: The first stage of our survey involved collecting samples of DUWL output water from 50 dental chair units (DCUs), and 2 samples of the incoming potable water. In October 2015, a one-time disinfection (1% Stabimed) of DUWLs was conducted. This was followed by collecting 10 control samples (survey stage 2). Results: From the total of 50 samples (survey stage 1), 18 samples (36.0 %) tested positive for Legionella spp. Following the disinfection, nine of the ten samples no longer showed any presence of Legionella. Conclusion: Based on culture results, the one-time disinfection (1% Stabimed) was effective. We are unable to comment on the duration of positive effect of disinfection on the occurrence of Legionella spp. in the outlet water. It was a one-time survey.


Prevalence of Legionella Species Isolated from Shower Water in Public Bath Facilities in Toyama Prefecture, Japan

Kanatani JI, Isobe J, Norimoto S, Kimata K, Mitsui C, Amemura-Maekawa J, Kura F, Sata T, Watahiki M.

Department of Bacteriology, Toyama Institute of Health, 17-1 Nakataikoyama, Imizu-City, Toyama, Japan.

J Infect Chemother 2017 May;23(5):265-270.

Abstract: Aims: We investigated the prevalence of Legionella spp. isolated from shower water in public bath facilities in Toyama Prefecture, Japan. In addition, we analyzed the genetic diversity among Legionella pneumophila isolates from shower water as well as the genetic relationship between isolates from shower water and from stock strains previously analyzed from sputum specimens. Methods: The isolates were characterized using serogrouping, 16S rRNA gene sequencing, and sequence-based typing. Results: Legionella spp. were isolated from 31/91 (34.1%) samples derived from 17/37 (45.9%) bath facilities. Isolates from shower water and bath water in each public bath facility were serologically or genetically different, indicating that we need to isolate several L. pneumophila colonies from both bath and shower water to identify public bath facilities as sources of legionellosis. The 61 L. pneumophila isolates from shower water were classified into 39 sequence types (STs) (index of discrimination = 0.974), including 19 new STs. Among the 39 STs, 12 STs match clinical isolates in the European Working Group for Legionella Infections database. Notably, ST505 L. pneumophila SG 1, a strain frequently isolated from patients with legionellosis and from bath water in this area, was isolated from shower water. Conclusions: Pathogenic L. pneumophila strains including ST505 strain were widely distributed in shower water in public bath facilities, with genetic diversity showing several different origins. This study highlights the need to isolate several L. pneumophila colonies from both bath water and shower water to identify public bath facilities as infection sources in legionellosis cases.


Survival of Legionella in Earthquake-Induced Soil Disturbance (Liquefaction) in Residential Areas, Christchurch, New Zealand: Implications for Disease

Graham FF, Harte DJ.

Department of Public Health, University of Otago, Wellington; Environmental Health, Regulation Health Protection and Emergency Management Division, Department of Health and Human Services, Melbourne, Australia.

N Z Med J 2017 May;130(1455):51-64.

Abstract: Aim: To investigate a possible link between liquefaction dust exposure and the noticeable increase in legionellosis cases in response to major earthquakes in 2010 and 2011 that resulted in widespread soil disturbance (liquefaction) in parts of Christchurch, New Zealand. Method: We culture tested liquefaction-affected soil for Legionella spp. in the six months following the first earthquake in 2010. Thirty silt samples were collected randomly from locations within Christchurch's metropolitan area that were affected by liquefaction. The samples were tested to determine the presence of Legionella using qualitative and quantitative methods. Liquefaction-affected soil samples from three sites were further subjected to particle size distribution analysis and determination of major oxides. A controlled field study was established using six silt samples and one control (commercial compost), seeded with a wild-type strain of Legionella bozemanae serogroup (sg) 1 and persistence monitored over a 60-day period by culturing for the presence of Legionella. Dry matter determinations were undertaken so that total Legionella could be calculated on a dry weight basis. Results: Legionella bacteria were undetectable after day one in the silt samples. However, L. bozemanae sg1 was detected in the control sample for the entire study period. Conclusion: This study showed that the liquefaction-affected soil could not contribute directly to the observed increase in legionellosis cases after the earthquakes due to its inability to support growth and survival of the Legionella bacteria.


Occurrence of Legionella in UK Household Showers

Collins S, Stevenson D, Bennett A, Walker J.

Biosafety, Air and Water Microbiology Group, National Infection Service, Public Health England, Porton Down, Salisbury, UK.

Int J Hyg Environ Health 2017 Apr;220(2 Pt B):401-406.

Abstract: Household water systems have been proposed as a source of sporadic, community acquired Legionnaires' disease. Showers represent a frequently used aerosol generating device in the domestic setting, yet little is known about the occurrence of Legionella spp. in these systems. This study has investigated the prevalence of Legionella spp. by culture and qPCR in UK household showers. Ninety-nine showers from 82 separate properties in the South of England were sampled. Clinically relevant Legionella spp. were isolated by culture in 8% of shower water samples representing 6% of households. Legionella pneumophila sg1 ST59 was isolated from two showers in one property and air sampling demonstrated its presence in the aerosol state. A further 31% of showers were positive by Legionella spp. qPCR. By multi-variable binomial regression modelling Legionella spp. qPCR positivity was associated with the age of the property (p=0.02), the age of the shower (p=0.01) and the frequency of use (p=0.09). The concentration of Legionella spp. detected by qPCR was shown to decrease with increased frequency of use (p=0.04) and more frequent showerhead cleaning (p=0.05). There was no association between Legionella spp. qPCR positivity and the cold water supply or the showerhead material (p=0.65 and p=0.71, respectively). Household showers may be important reservoirs of clinically significant Legionella and should be considered in source investigations. Simple public health advice may help to mitigate the risk of Legionella exposure in the domestic shower environment.


Annual Variations and Effects of Temperature on Legionella Spp. And Other Potential Opportunistic Pathogens in a Bathroom

Lu J, Buse H, Struewing I, Zhao A, Lytle D, Ashbolt N.

US EPA, Office of Research and Development, Cincinnati, OH, USA.

Environ Sci Pollut Res Int 2017 Jan;24(3):2326-2336.

Abstract: Opportunistic pathogens (OPs) in drinking water, like Legionella spp., mycobacteria, Pseudomonas aeruginosa, and free-living amobae (FLA) are a risk to human health, due to their post-treatment growth in water systems. To assess and manage these risks, it is necessary to understand their variations and environmental conditions for the water routinely used. We sampled premise tap (N cold=26, N hot=26) and shower (N shower=26) waters in a bathroom and compared water temperatures to levels of OPs via qPCR and identified Legionella spp. by 16S ribosomal RNA (rRNA) gene sequencing. The overall occurrence and cell equivalent quantities (CE L-1) of Mycobacterium spp. were highest (100%, 1.4×105), followed by Vermamoeba vermiformis (91%, 493), Legionella spp. (59%, 146), P. aeruginosa (14%, 10), and Acanthamoeba spp. (5%, 6). There were significant variations of OP's occurrence and quantities, and water temperatures were associated with their variations, especially for Mycobacterium spp., Legionella spp., and V. vermiformis. The peaks observed for Legionella, mainly consisted of Legionella pneumophila sg1 or Legionella anisa, occurred in the temperature ranged from 19 to 49°C, while Mycobacterium spp. and V. vermiformis not only co-occurred with Legionella spp. but also trended to increase with increasing temperatures. There were higher densities of Mycobacterium in first than second draw water samples, indicating their release from faucet/showerhead biofilm. Legionella spp. were mostly at detectable levels and mainly consisted of L. pneumophila, L. anisa, Legionella donaldsonii, Legionella tunisiensis, and an unknown drinking water isolate based on sequence analysis. Results from this study suggested potential health risks caused by opportunistic pathogens when exposed to warm shower water with low chlorine residue and the use of Mycobacterium spp. as an indicator of premise pipe biofilm and the control management of those potential pathogens.


Detection of Legionella-contaminated Aerosols in the Vicinity of a Bio-Trickling Filter of a Breeding Sow Facility - A Pilot Study

Walser SM, Brenner B, Wunderlich A, Tuschak C, Huber S, Kolb S, Niessner R, Seidel M, Höller C, Herr CEW.

Bavarian Health and Food Safety Authority, Occupational and Environmental Health, Epidemiology, Munich, Germany.

Sci Total Environ 2017 Jan;575:1197-1202.

Abstract: The urbanization of agricultural areas results in a reduction of distances between residential buildings and livestock farms. In the public debate, livestock farming is increasingly criticized due to environmental disturbance and odor nuisance originating from such facilities. One method to reduce odor and ammonia is by exhaust air treatment, for example, by biological exhaust air purification processes with bio-trickling filters filled with tap water. Higher temperatures in the summertime and the generation of biofilms are ideal growth conditions for Legionella. However, there are no studies on the presence of Legionella in the water of bio-trickling filters and the release of Legionella-containing aerosols. Therefore, the aim of this study was to investigate Legionella in wash water and emitted bioaerosols of a bio-trickling filter system of a breeding sow facility. For this purpose, measurements were carried out using a cyclone sampler. In addition, samples of wash water were taken. Legionella were not found by culture methods. However, using molecular biological methods, Legionella spp. could be detected in wash water as well as in bioaerosol samples. With antibody-based methods, Legionella pneumophila were identified. Further studies are needed to investigate the environmental health relevance of Legionella-containing aerosols emitted by such exhaust air purification systems.