Occurrence of Legionella in groundwater used for sprinkler irrigation in Southern Italy

Environmental Monitoring of Legionella in Hospitals in the Campania Region: A 5-Year Study

Legionella is a pathogen that colonizes soils, freshwater, and building water systems. People who are most affected are those with immunodeficiencies, so it is necessary to monitor its presence in hospitals. The purpose of this study was to evaluate the presence of Legionella in water samples collected from hospitals in the Campania region, Southern Italy. A total of 3365 water samples were collected from January 2018 to December 2022 twice a year in hospital wards from taps and showers, tank bottoms, and air-treatment units. Microbiological analysis was conducted in accordance with the UNI EN ISO 11731:2017, and the correlations between the presence of Legionella and water temperature and residual chlorine were investigated. In total, 708 samples (21.0%) tested positive. The most represented species was L. pneumophila 2-14 (70.9%). The serogroups isolated were 1 (27.7%), 6 (24.5%), 8 (23.3%), 3 (18.9%), 5 (3.1%), and 10 (1.1%). Non-pneumophila Legionella spp. represented 1.4% of the total. Regarding temperature, the majority of Legionella positive samples were found in the temperature range of 26.0-40.9 °C. An influence of residual chlorine on the presence of the bacterium was observed, confirming that chlorine disinfection is effective for controlling contamination. The positivity for serogroups other than serogroup 1 suggested the need to continue environmental monitoring of Legionella and to focus on the clinical diagnosis of other serogroups.

Microbiological quality of irrigation water for cultivation of fruits and vegetables: An overview of available guidelines, water testing strategies and some factors that influence compliance

Contaminated irrigation water is among many potential vehicles of human pathogens to food plants, constituting significant public health risks especially for the fresh produce category. This review discusses some available guidelines or regulations for microbiological safety of irrigation water, and provides a summary of some common methods used for characterizing microbial contamination. The goal of such exploration is to understand some of the considerations that influence formulation of water testing guidelines, describe priority microbial parameters particularly with respect to food safety risks, and attempt to determine what methods are most suitable for their screening. Furthermore, the review discusses factors that influence the potential for microbiologically polluted irrigation water to pose substantial risks of pathogenic contamination to produce items. Some of these factors include type of water source exploited, irrigation methods, other agro ecosystem features/practices, as well as pathogen traits such as die-off rates. Additionally, the review examines factors such as food safety knowledge, other farmer attitudes or inclinations, level of social exposure and financial circumstances that influence adherence to water testing guidelines and other safe water application practices. A thorough understanding of relevant risk metrics for the application and management of irrigation water is necessary for the development of water testing criteria. To determine sampling and analytical approach for water testing, factors such as agricultural practices (which differ among farms and regionally), as well as environmental factors that modulate how water quality may affect the microbiological safety of produce should be considered. Research and technological advancements that can improve testing approach and the determination of target levels for hazard characterization or description for the many different pollution contexts as well as farmer adherence to testing requirements, are desirable.

Legionellosis risk-an overview of Legionella spp. habitats in Europe

An increase in the number of reports of legionellosis in the European Union and the European Economic Area have been recorded in recent years. The increase in cases is significant: from 6947 reports in 2015 to 11,298 in 2019. This is alarming as genus Legionella, which comprises a large group of bacteria inhabiting various aquatic systems, poses a serious threat to human health and life, since more than 20 species can cause legionellosis, with L. pneumophila being responsible for the majority of cases. The ability to colonize diverse ecosystems makes the eradication of these microorganisms difficult. A detailed understanding of the Legionella habitat may be helpful in the effective control of this pathogen. This paper provides an overview of Legionella environments in Europe: natural (lakes, groundwater, rivers, compost, soil) and anthropogenic (fountains, air humidifiers, water supply systems), and the role of Legionella spp. in nosocomial infections, which are potentially fatal for children, the elderly and immunocompromised patients.

Design and operational considerations in response to Legionella occurrence in Las Vegas Valley groundwater

Legionella occurrence monitoring is not required by United States Environmental Protection Agency (USEPA) drinking water regulations, and few occurrence studies exist for Legionella in source water or distribution systems. Legionella occurrence was monitored in Las Vegas Valley (Las Vegas, Nevada, USA) drinking water sources, including non-treated surface water, seasonal groundwater (61 wells, before and after chlorination), finished water (after treatment at water treatment facilities), and chlorinated distribution system water (at 9 reservoirs and 75 sample locations throughout the network). Legionella pneumophila was detected at least once at each of the wells sampled before chlorination, with an overall positivity rate of 38% (343/908). During well start-up (time<2 hours; turbidity>3 NTU), L. pneumophila concentrations averaged 2,792±353 MPN/100 mL, with a median of 105 MPN/100 mL, and range of <1 to 90,490 MPN/100 mL across 61 seasonally operated (typically April-October) groundwater wells. After initial flushing (turbidity<3 NTU), the average concentration decreased by more than two orders of magnitude to 24±3 MPN/100 mL but ranged from <1 to >2,273 MPN/100 mL. This trend indicates that stagnation (up to 391 days) contributed to greater initial concentrations, and flushing alone was incapable of complete L. pneumophila elimination. L. pneumophila concentration was significantly, positively correlated with total aqueous adenosine triphosphate (ATP) (p<0.00001, r=0.41-0.71), turbidity (p<0.00001, r=0.27-0.51), orthophosphate (p=0.35-0.076, r=0.51-0.59), and pump depth (p=0.032, r=0.40). During a full-scale assessment of chlorination (Ct=0.7 to 10.5 mg-min/L; T=26.6-28.1°C), substantial reduction of Legionella spp. (up to 2.5 logs) was observed; although, detectable concentrations were still measured. Extrapolating from a Chick-Watson model (log inactivation=0.28*(Ct); R²=0.87) constructed from the full-scale chlorination results, 3- and 4-log inactivation in Las Vegas Valley groundwater would require 10.8 and 14.3 mg-min/L, respectively; at least 3-log inactivation was required to bring Legionella spp. to below detection at the studied well. Chlorine exposure (Ct=0.1 to 10.9 mg-min/L) at most wells discharging directly to the distribution system was insufficient to fully inactivate Legionella spp. After discussing these findings with the state regulatory agency, direct-to-distribution wells (38 of 61 wells) remained out of operation; the distribution system, wells, and reservoirs were monitored for Legionella and chlorine residual, and additional treatment scenarios were identified for further evaluation. Legionella was either not detected or was well controlled in surface water, finished effluent from the drinking water treatment plant, chlorinated reservoirs, and the chlorinated distribution system. This study emphasizes the importance of utility-driven, non-regulatory research in order to protect public health and also identifies the need for greater occurrence monitoring and guidance for Legionella in groundwater supplies.

Water Age Effects on the Occurrence and Concentration of Legionella Species in the Distribution System, Premise Plumbing, and the Cooling Towers

In this study, droplet digital PCR^TM (ddPCR^TM) was used to characterize total Legionella spp. and five specific Legionella species from source (groundwater) to exposure sites (taps and cooling towers). A total of 42–10 L volume water samples were analyzed during this study: 12 from a reservoir (untreated groundwater and treated water storage tanks), 24 from two buildings (influents and taps), and six from cooling towers, all part of the same water system. The approximate water age (time in the system) for all sample locations are as follows: ~4.5, 3.4, 9.2, 20.8, and 23.2 h (h) for the groundwater to the reservoir influent, reservoir influent to the reservoir effluent, reservoir effluent to building Fa (building names are abbreviated to protect the privacy of site location), building ERC and the cooling towers, respectively. Results demonstrated that gene copies of Legionella spp. (23S rRNA) were significantly higher in the cooling towers and ERC building (p < 0.05) relative to the reservoir and building Fa (closest to reservoir). Legionella spp. (23S rRNA) were found in 100% (42/42) of water samples at concentrations ranging from 2.2 to 4.5 Log10 GC/100 mL. More specifically, L. pneumophila was found in 57% (24/42) of the water samples, followed by L. bozemanii 52% (22/42), L. longbeachae 36% (15/42), L. micdadei 23% (10/42) and L. anisa 21% (9/42) with geometric mean concentrations of 1.7, 1.7, 1.4, 1.6 and 1.7 Log₁₀ GC/100 mL, respectively. Based on this study, it is hypothesized that water age in the distribution system and the premise-plumbing system as well as building management plays a major role in the increase of Legionella spp., (23S rRNA) and the diversity of pathogenic species found as seen in the influent, and at the taps in the ERC building—where the building water quality was most comparable to the industrial cooling towers. Other pathogenic Legionella species besides L.pneumophila are also likely amplifying in the system; thus, it is important to consider other disease relevant species in the whole water supply system—to subsequently control the growth of pathogenic Legionella in the built water environment.

Legionella Occurrence beyond Cooling Towers and Premise Plumbing

Legionella is an environmental pathogen that is responsible for respiratory disease and is a common causative agent of water-related outbreaks. Due to their ability to survive in a broad range of environments, transmission of legionellosis is possible from a variety of sources. Unfortunately, a disproportionate amount of research that is devoted to studying the occurrence of Legionella in environmental reservoirs is aimed toward cooling towers and premise plumbing. As confirmed transmission of Legionella has been linked to many other sources, an over-emphasis on the most common sources may be detrimental to increasing understanding of the spread of legionellosis. This review aims to address this issue by cataloguing studies which have examined the occurrence of Legionella in less commonly investigated environments. By summarizing and discussing reports of Legionella in fresh water, ground water, saltwater, and distribution system drinking water, future environmental and public health researchers will have a resource to aid in investigating these pathogens in relevant sources.

Integrated approach for legionellosis risk analysis in touristic-recreational facilities

Legionellosis is a severe pneumonia caused by the inhalation of aerosols containing Legionella, Gram-negative bacteria present in the water systems of touristic-recreational facilities. The purpose of this study was to develop a scoring tool to predict the risk of both environmental contamination and Legionnaires' disease cases in such facilities in the Apulia region of southern Italy. We analyzed 47 structural and management parameters/risk factors related to the buildings, water systems, and air conditioning at the facilities. A Poisson regression model was used to compute an overall risk score for each facility with respect to three outcomes: water samples positive for Legionella (risk score range: 7-54), water samples positive for Legionella with an average load exceeding 1000 colony-forming units per liter (CFU/L) (risk score range: 22-179,871), and clinical cases of Legionnaire's disease (risk score range: 6-31). The cut-off values for three outcomes were determined by receiver operating characteristic curves (first outcome, samples positive for Legionella in a touristic-recreational facility: 19; second outcome, samples positive for Legionella in a touristic-recreational facility with an average load exceeding 1000 CFU/L: 2062; third outcome, clinical cases of Legionnaire's disease in a touristic-recreational facility: 22). Above these values, there was a significant probability of observing the outcome. We constructed this predictive model using 70% of a large dataset (18 years of clinical and environmental surveillance) and tested the model on the remaining 30% of the dataset to demonstrate its reliability. Our model enables the assessment of risk for a touristic facility and the creation of a conceptual framework to link the risk analysis with prevention measures.

Cooccurrence of Five Pathogenic Legionella spp. and Two Free-Living Amoebae Species in a Complete Drinking Water System and Cooling Towers

Pathogenic Legionella species grow optimally inside free-living amoebae to concentrations that increase risks to those who are exposed. The aim of this study was to screen a complete drinking water system and cooling towers for the occurrence of Acanthamoeba spp. and Naegleria fowleri and their cooccurrence with Legionella pneumophila, Legionella anisa, Legionella micdadei, Legionella bozemanii, and Legionella longbeachae. A total of 42 large-volume water samples, including 12 from the reservoir (water source), 24 from two buildings (influents to the buildings and exposure sites (taps)), and six cooling towers were collected and analyzed using droplet digital PCR (ddPCR). N. fowleri cooccurred with L. micdadei in 76 (32/42) of the water samples. In the building water system, the concentrations of N. fowleri and L. micdadei ranged from 1.5 to 1.6 Log₁₀ gene copies (GC)/100 mL, but the concentrations of species increased in the cooling towers. The data obtained in this study illustrate the ecology of pathogenic Legionella species in taps and cooling towers. Investigating Legionella’s ecology in drinking and industrial waters will hopefully lead to better control of these pathogenic species in drinking water supply systems and cooling towers.

The Role of Lipids in Legionella-Host Interaction

Legionella are Gram-stain-negative rods associated with water environments: either natural or man-made systems. The inhalation of aerosols containing Legionella bacteria leads to the development of a severe pneumonia termed Legionnaires' disease. To establish an infection, these bacteria adapt to growth in the hostile environment of the host through the unusual structures of macromolecules that build the cell surface. The outer membrane of the cell envelope is a lipid bilayer with an asymmetric composition mostly of phospholipids in the inner leaflet and lipopolysaccharides (LPS) in the outer leaflet. The major membrane-forming phospholipid of Legionella spp. is phosphatidylcholine (PC)-a typical eukaryotic glycerophospholipid. PC synthesis in Legionella cells occurs via two independent pathways: the N-methylation (Pmt) pathway and the Pcs pathway. The utilisation of exogenous choline by Legionella spp. leads to changes in the composition of lipids and proteins, which influences the physicochemical properties of the cell surface. This phenotypic plasticity of the Legionella cell envelope determines the mode of interaction with the macrophages, which results in a decrease in the production of proinflammatory cytokines and modulates the interaction with antimicrobial peptides and proteins. The surface-exposed O-chain of Legionella pneumophila sg1 LPS consisting of a homopolymer of 5-acetamidino-7-acetamido-8-O-acetyl-3,5,7,9-tetradeoxy-l-glycero-d-galacto-non-2-ulosonic acid is probably the first component in contact with the host cell that anchors the bacteria in the host membrane. Unusual in terms of the structure and function of individual LPS regions, it makes an important contribution to the antigenicity and pathogenicity of Legionella bacteria.

Management of Microbiological Contamination of the Water Network of a Newly Built Hospital Pavilion

The good installation, as well as commissioning plan, of a water network is a crucial step in reducing the risk of waterborne diseases. The aim of this study was to monitor the microbiological quality of water from a newly built pavilion before it commenced operation. Overall, 91 water samples were tested for coliforms, Escherichia coli, enterococci, Pseudomonas aeruginosa and Legionella at three different times: T0 (without any water treatment), T1 (after treatment with hydrogen peroxide and silver ions at initial concentration of 20 mg/L and after flushing of water for 20 min/day for seven successive days) and T2 (15 days later). Coliforms were detected in 47.3% of samples at T0, 36.3% at T1 and 4.4% at T2. E. coli was isolated in 4.4% of the samples only at T1, while enterococci appeared in 12.1% of the samples at T1 and in 2.2% at T2. P. aeruginosa was isolated in 50.5% of the samples at T0, 29.7% at T1 and 1.1% at T2. Legionella pneumophila serogroup 8 was isolated in 80.2% of the samples at T0, 36.3% at T1 and 2.2% at T2. Our results confirmed the need for a water safety plan in new hospital pavilions to prevent the risk of waterborne diseases.

Impact of lockdown on the microbiological status of the hospital water network during COVID-19 pandemic

The COVID-19 pandemic started in China in early December 2019, and quickly spread around the world. The epidemic gradually started in Italy at the end of February 2020, and by May 31, 2020, 232,664 cases and 33,340 deaths were confirmed. As a result of this pandemic, the Italian Ministerial Decree issued on March 11, 2020, enforced lockdown; therefore, many social, recreational, and cultural centers remained closed for months. In Apulia (southern Italy), all non-urgent hospital activities were suspended, and some wards were closed, with a consequent reduction in the use of the water network and the formation of stagnant water. This situation could enhance the risk of exposure of people to waterborne diseases, including legionellosis. The purpose of this study was to monitor the microbiological quality of the water network (coliforms, E. coli, Enterococci, P. aeruginosa, and Legionella) in three wards (A, B and C) of a large COVID-19 regional hospital, closed for three months due to the COVID-19 emergency. Our study revealed that all three wards' water network showed higher contamination by Legionella pneumophila sg 1 and sg 6 at T1 (after lockdown) compared to the period before the lockdown (T0). In particular, ward A at T1 showed a median value = 5600 CFU/L (range 0-91,000 CFU/L) vs T0, median value = 75 CFU/L (range 0-5000 CFU/L) (p-value = 0.014); ward B at T1 showed a median value = 200 CFU/L (range 0-4200 CFU/L) vs T0, median value = 0 CFU/L (range 0-300 CFU/L) (p-value = 0.016) and ward C at T1 showed a median value = 175 CFU/L (range 0-22,000 CFU/L) vs T0, median value = 0 CFU/L (range 0-340 CFU/L) (p-value < 0.001). In addition, a statistically significant difference was detected in ward B between the number of positive water samples at T0 vs T1 for L. pneumophila sg 1 and sg 6 (24% vs 80% p-value < 0.001) and for coliforms (0% vs 64% p-value < 0.001). Moreover, a median value of coliform load resulted 3 CFU/100 ml (range 0-14 CFU/100 ml) at T1, showing a statistically significant increase versus T0 (0 CFU/100 ml) (p-value < 0.001). Our results highlight the need to implement a water safety plan that includes staff training and a more rigorous environmental microbiological surveillance in all hospitals before occupying a closed ward for a longer than one week, according to national and international guidelines.

Groundwater level prediction in Apulia region (Southern Italy) using NARX neural network

In the Mediterranean area, the high water demand frequently leads to an excessive exploitation of the water resource, which involves a qualitative degradation of the freshwaters stored in coastal karst aquifers, as a result of phenomena such as sea saltwater intrusion. In this study, the NARX network was used to predict the daily groundwater level fluctuation for 76 monitored wells located on the Apulian territory. A preliminary analysis on reference wells was performed in order to assess the impact on the groundwater level prediction of two input parameters, rainfall and evapotranspiration, and the sensitivity to changes of training algorithm and input time delay. Based on the findings of the preliminary analysis, a comprehensive regional analysis and extensive sub-regional analyses were performed, proving the reliability of the NARX-BR network for the groundwater level prediction in wells located on different hydrogeological structures. The accurate results obtained for the Apulia region suggest the NARX network application for groundwater level prediction in other areas affected by groundwater resource management issues.

Groundwater pollution: Occurrence, detection, and remediation of organic and inorganic pollutants

Groundwater pollution is a result of natural and anthropogenic activities. While the elevated levels of various inorganic constituents could be attributed to natural processes, such as geological weathering and aquifer characteristics, many times, anthropogenic activities also substantially pollute the groundwater. On the contrary, the occurrence of organic pollutants is primarily due to various anthropogenic activities. Extensive groundwater mining, the hydraulic connection between groundwater and other surface water bodies, and leaking underground buried infrastructure also contribute to groundwater pollution. Water resources are scarce commodities, and preserving groundwater quality is of critical concern. This paper documents instances of groundwater quality impact during the year 2019 due to both natural and anthropogenic activities throughout the world. PRACTITIONER POINTS: Groundwater pollution problems reported during the year 2019 are reviewed and documented. Occurrence of organic, inorganic, and microbial pollutants in groundwater is reported. Remediation technologies for selected inorganic pollutants are reviewed and documented.

Safety in Wine Production: A Pilot Study on the Quality Evaluation of Prosecco Wine in the Framework of UE Regulation

In Italy, wine production is considered a sector of excellence, where the wines' appreciable sensory features are favored by environmental factors, including weather and climate conditions, which benefit territories with a specific vocation. The whole chain involves many economic and agri-food sector operators, and requires an in-depth assessment of specific risks for identifying critical points, keeping the entire production process under control, and ensuring product traceability. This article describes the results of a pilot study conducted in the Prosecco DOCG (Designations of Controlled and Guaranteed Origin) area, concerning the detection of residues of plant protection products in fifty wine bottles. Although considerably below the maximum residue levels, all the samples tested were positive, ranging from two to five active substances detected in each sample. In addition to the provisions of the European Community legislation, this paper critically evaluates some best practices models that are already used by the Wine Federations of Italy, with the aim of identifying advantages of and areas for improvement in production methods, applicable to raw materials reception, rasping, storage, and bottling phases, in order to guarantee product safety and quality.

Legionella Detection in Water Networks as per ISO 11731:2017: Can Different Filter Pore Sizes and Direct Placement on Culture Media Influence Laboratory Results?

Determination of Legionella concentrations in water networks is useful for predicting legionellosis risks. The standard culture technique using concentration with membranes filters is the most commonly used method for environmental surveillance of Legionella. The aim of this study was to verify whether filtration with different filter pore sizes (0.2 and 0.45 µm) according to (ISO) 11731:2017, followed by directly placing them on culture media, can influence Legionella detection. Three laboratories participated in an experimental study that tested a known suspension of Legionella pneumophila (Lpn) serogroup 1 (ATCC 33152) (approximate final cell density of 15 CFU/mL). E. coli (ATCC 11775) and Pseudomonas aeruginosa (ATCC 25668) were included as control tests. The average (95% CI) percentage of recovery of Lpn was 65% using 0.45-µm filters and 15% using 0.2-µm filters (p < 0.0001). For control tests, the average (95% CI) percentage of recovery was higher with 0.45 vs. 0.2 µm filters: 97% vs. 64% for Escherichia coli (p < 0.00001) and 105% vs. 97% (p = 0.0244) for P. aeruginosa. Our results showed that the 0.45-µm filters provided the greatest detection of Legionella. Because the current national guidelines leave the choice of membrane porosity to the operator, experimental studies are important for directing operators towards a conscious choice to standardize Legionella environmental surveillance methods.

Legionella and legionellosis in touristic-recreational facilities: Influence of climate factors and geostatistical analysis in Southern Italy (2001-2017)

Legionella is the causative agent of Legionnaires' disease, a flu-like illness normally acquired following inhalation or aspiration of contaminated water aerosols. Our recent studies revealed that climatic parameters can increase the number of reported cases of community-acquired Legionnaires' disease. Here, we evaluated the presence of Legionella in water networks and the distribution of Legionnaires' disease cases associated with touristic-recreational facilities in the Apulia region (southern Italy) during the period 2001-2017 using geostatistical and climatic analyses. Geostatistical analysis data revealed that the area with the highest concentration of Legionella in water systems also had the greatest number of cases of Legionnaires' disease associated with touristic-recreational facilities. Climatic analysis showed that higher daily temperature excursion (difference between maximum and minimum temperature) on the day of sampling was more often associated with Legionella-positive samples than Legionella-negative samples. In addition, our data highlighted an increased risk of Legionnaires' disease with increases in precipitation and average temperature and with decreases in daily temperature excursion (difference between maximum and minimum temperature over the course of 24 h in the days of incubation period of disease) and minimum temperature. Healthcare professionals should be aware of this phenomenon and be particularly vigilant for cases of community-acquired pneumonia during such climatic conditions and among the tourist population. The innovative geo-statistical approach used in this study could be applied in other contexts when evaluating the effects of climatic conditions on the incidence of Legionella infections.