Legionella pneumophila occurrence in drinking water supplied by private wells

Multi-criterion analysis of the effect of physico-chemical microbiological agents on Legionella detection in hotel water distribution systems in Crete

Introduction

Water distribution systems in hotels have been related to outbreaks caused by Legionella spp. Certain measures, including disinfection by chlorination, maintaining increased temperatures are usually undertaken to prevent Legionella outbreaks. However, these preventive strategies are not always effective, since there are several factors (e.g., synergistic interactions with other microbes, physico-chemical factors, biofilm formation, availability of nutrients) that promote survival and proliferation of the pathogen in water pipes., Accordingly, there is a need of a holistic approach in development of preventive models for Legionella outbreaks associated with water distribution systems.

Methods

Water samples were collected from hotel water systems and were tested for the presence of Legionella, E. coli, total coliforms, total mesophilic count and Pseudomonas. In each sample, temperature and chlorine were also tested. Other epidemiological factors were additionally recorded including number of rooms, stars, proximity of sampling point to the boiler, etc. Data were processed by generalized linear analysis, and modeling based on logistic regression analysis to identify independent predictive factors associated with the presence of Legionella in hotel water systems.

Results

According to the generalized linear model, temperature affected (p<0.05) the presence of Legionella regardless of the species or the water supply (hot or cold). Additionally, opportunistic (P. aeruginosa) or non-opportunistic (E. coli, coliforms) pathogens were significantly associated (p<0.05) with the presence of all Legionella species. Temperature also exhibited a positive effect to all pathogens tested except for Pseudomonas according to the linear model. Multivariate analysis showed that Pseudomonas, total coliforms, HPC and temperature had a statistically significant effect on the presence of Legionella. Based on a binomial model, cold water had a positive effect on Legionella. Type of sampling and proximity of the sample to the boiler seemed to pose different effect on Legionella depending on the cfu/L. The number of hotel stars and rooms did not appear to have any effect in all tested models.

Discussion

Collectively, these results indicate the need for development of individualized water safety plans tailored by the presence of other microbiological agents, and unique physico-chemical factors, which could facilitate the survival of Legionella.in hotel water systems.

A Critical Review on the Factors that Influence Opportunistic Premise Plumbing Pathogens: From Building Entry to Fixtures in Residences

Residential buildings provide unique conditions for opportunistic premise plumbing pathogen (OPPP) exposure via aerosolized water droplets produced by showerheads, faucets, and tubs. The objective of this review was to critically evaluate the existing literature that assessed the impact of potentially enhancing conditions to OPPP occurrence associated with residential plumbing and to point out knowledge gaps. Comprehensive studies on the topic were found to be lacking. Major knowledge gaps identified include the assessment of OPPP growth in the residential plumbing, from building entry to fixtures, and evaluation of the extent of the impact of typical residential plumbing design (e.g., trunk and branch and manifold), components (e.g., valves and fixtures), water heater types and temperature setting of operation, and common pipe materials (copper, PEX, and PVC/CPVC). In addition, impacts of the current plumbing code requirements on OPPP responses have not been assessed by any study and a lack of guidelines for OPPP risk management in residences was identified. Finally, the research required to expand knowledge on OPPP amplification in residences was discussed.

Microbial Water Quality Assessment of Private Wells Using 16S rRNA Gene Amplicon Sequencing with a Nanopore Sequencer

Private wells are used daily worldwide as convenient household water sources. In Japan, where water supply coverage is high, well water is occasionally used for non-potable purposes, such as irrigation and watering. Currently, the main microbiological test of well water is designed to detect Escherichia coli, which is an indicator of fecal contamination, using culture methods. Water use such as watering generates bioaerosols, which may cause airborne infection. However, many causative bacteria of aerosol-derived infections, such as Legionella spp., are difficult to detect using culture methods. Thus, more comprehensive modern assessment is desirable for securing the microbiological quality of well water. Here, the bacterial community structure of five private wells located in different environments was examined using the rapid and portable MinION sequencer, which enabled us to identify bacteria to the species level based on full-length 16S ribosomal RNA (rRNA) gene sequences. The results revealed the differences in the bacterial community structures of water samples from the five wells and detected Legionella pneumophila and Aeromonas hydrophila as new candidate microbial indicators. The comprehensive analysis method used in this study successfully detected bacteria causing opportunistic infections, which are difficult to detect by conventional methods. This approach is expected to be routinely applied in the future as a highly accurate method for assessing the microbiological quality of private well water.

The antimicrobial resistance profiles of Escherichia coli and Pseudomonas aeruginosa isolated from private groundwater wells in the Republic of Ireland

The role of the natural environment in the dissemination of antimicrobial resistant bacteria has been increasingly recognised in the literature. However, knowledge surrounding the critical factors and mechanisms mediating their occurrence is still limited, particularly in relatively 'pristine' groundwater environments. In the Republic of Ireland (RoI), a country characterised by high groundwater reliance, household-based (unregulated) wells provide drinking water to 11% of the population. These private wells are generally located in rural areas, where the risk of microbiological contamination is high due to intensive agricultural practices and high reliance on domestic wastewater treatment systems; both of which are also potential sources of antimicrobials and antimicrobial resistant bacteria. Accordingly, the current research sought to elucidate current rates of antimicrobial resistant bacteria and the principal factors associated with their presence in private wells in the RoI. A total of 250 samples (from 132 wells nationwide) were assessed for the presence of faecal (Escherichia coli) and environmental (Pseudomonas aeruginosa) bacteria, with single isolates from each contaminated sample tested phenotypically against 18 and 9 antimicrobials, respectively. Findings show that while 16.7% of E. coli (n = 8/48) were categorically resistant to ≥1 antimicrobial, with a further 79.2% classified as intermediately resistant, no categorical resistance was found among P. aeruginosa isolates (n = 0/6), with just one intermediately resistant isolate detected. Multivariate regression modelling indicates significantly higher odds of resistant E. coli detection in concurrence with elevated cattle density (OR = 1.028, p = 0.032), aligning with findings of highest resistance rates to veterinary antimicrobials (e.g., streptomycin = 14.6%, tetracycline = 12.5%, and ampicillin = 12.5%). Multivariate model results also suggest overland flow culminating in direct wellhead ingress as a primary ingress mechanism for resistant E. coli. Study findings may inform groundwater source protection initiatives and antimicrobial resistance surveillance moving forward.

Occurrence of opportunistic pathogens in private wells after major flooding events: A four state molecular survey

Private wells can become contaminated with waterborne pathogens during flooding events; however, testing efforts focus almost exclusively on fecal indicator bacteria. Opportunistic pathogens (OPs), which are the leading cause of identified waterborne disease in the United States, are understudied in private wells. We conducted a quantitative polymerase chain reaction survey of Legionella spp., L. pneumophila, Mycobacterium spp., M. avium, Naegleria fowleri, and shiga toxin-producing Escherichia coli gene markers and total coliform and E. coli in drinking water supplied by private wells following the Louisiana Floods (2016), Hurricane Harvey (2017), Hurricane Irma (2017), and Hurricane Florence (2018). Self-reported well characteristics and recovery status were collected via questionnaires. Of the 211 water samples collected, 40.3% and 5.2% were positive for total coliform and E. coli, which were slightly elevated positivity rates compared to prior work in coastal aquifers. DNA markers for Legionella and Mycobacterium were detected in 54.5% and 36.5% of samples, with L. pneumophila and M. avium detected in 15.6% and 17.1%, which was a similar positivity rate relative to municipal system surveys. Total bacterial 16S rRNA gene copies were positively associated with Legionella and Mycobacterium, indicating that conditions that favor occurrence of general bacteria can also favor OPs. N. fowleri DNA was detected in 6.6% of samples and was the only OP that was more prevalent in submerged wells compared to non-submerged wells. Self-reported well characteristics were not associated with OP occurrence. This study exposes the value of routine baseline monitoring and timely sampling after flooding events in order to effectively assess well water contamination risks.

The Presence of Opportunistic Premise Plumbing Pathogens in Residential Buildings: A Literature Review

Opportunistic premise plumbing pathogens (OPPP) are microorganisms that are native to the plumbing environment and that present an emerging infectious disease problem. They share characteristics, such as disinfectant resistance, thermal tolerance, and biofilm formation. The colonisation of domestic water systems presents an elevated health risk for immune-compromised individuals who receive healthcare at home. The literature that has identified the previously described OPPPs (Aeromonas spp., Acinetobacter spp., Helicobacter spp., Legionella spp., Methylobacterium spp., Mycobacteria spp., Pseudomonas spp., and Stenotrophomonas spp.) in residential drinking water systems were systematically reviewed. By applying the Preferred reporting items for systematic reviews and meta-analyses guidelines, 214 studies were identified from the Scopus and Web of Science databases, which included 30 clinical case investigations. Tap components and showerheads were the most frequently identified sources of OPPPs. Sixty-four of these studies detected additional clinically relevant pathogens that are not classified as OPPPs in these reservoirs. There was considerable variation in the detection methods, which included traditional culturing and molecular approaches. These identified studies demonstrate that the current drinking water treatment methods are ineffective against many waterborne pathogens. It is critical that, as at-home healthcare services continue to be promoted, we understand the emergent risks that are posed by OPPPs in residential drinking water. Future research is needed in order to provide consistent data on the prevalence of OPPPs in residential water, and on the incidence of waterborne homecare-associated infections. This will enable the identification of the contributing risk factors, and the development of effective controls.

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.

A review of legionnaires' disease and public water systems - Scientific considerations, uncertainties and recommendations

Legionella is an opportunistic premise plumbing pathogen and causative agent of a severe pneumonia called Legionnaires' Disease (LD). Cases of LD have been on the rise in the U.S. and globally. Although Legionella was first identified 45 years ago, it remains an 'emerging pathogen." Legionella is part of the normal ecology of a public water system and is frequently detected in regulatory-compliant drinking water. Drinking water utilities, regulators and public health alike are increasingly required to have a productive understanding of the evolving issues and complex discussions of the contribution of the public water utility to Legionella exposure and LD risk. This review provides a brief overview of scientific considerations important for understanding this complex topic, a review of findings from investigations of public water and LD, including data gaps, and recommendations for professionals interested in investigating public water utilities. Although the current literature is inconclusive in identifying a public water utility as a sole source of an LD outbreak, the evidence is clear that minimizing growth of Legionella in public water utilities through proper maintenance and sustained disinfectant residuals, throughout all sections of the water utility, will lead to a less conducive environment for growth of the bacteria in the system and the buildings they serve.

Evaluation of private well contaminants in an underserved North Carolina community

On-site sewage treatment systems can be an important source of antibiotic resistant bacteria and organic micropollutants into adjacent groundwater. Due to the frequent proximity of private wells to septic systems, this contamination is a concern to communities that do not have access to public municipal services. In both rural and urban environments, low-income communities, indigenous communities and those of color are disproportionately affected by well contamination. The objective of this study was to assess well water quality in an underserved North Carolina community by performing a comprehensive evaluation of microbial and organic micropollutant occurrence and determining possible sources of contamination. Well water, septic tanks, and adjacent municipal water were sampled. Culture- and molecular biology-based microbial analysis and non-targeted, high resolution mass spectrometry chemical analysis were conducted to assess water quality in comparison to nearby municipal water. Three of thirteen homes had between 1 and 6.3 CFUs/100 mL of E. coli and two homes had fecal bacteria resistant to antibiotics in their well water. The water of four homes showed concentrations of the artificial sweetener sucralose, a wastewater tracer, higher than the municipal water (range ~ 60-1500 ng L^-1). The human-specific HF183 fecal marker was detected in 79% of the wells tested. The presence of pharmaceuticals and personal care products in four home wells, along with the presence of pesticides and insecticides in two homes, suggest possible contamination from septic tanks and lawn care runoff. The implications of this work highlight the necessity of wider scale contaminant evaluation of well water.

Legionella and Biofilms-Integrated Surveillance to Bridge Science and Real-Field Demands

Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy.

Comparative study of Legiolert with ISO 11731-1998 standard method-conclusions from a Public Health Laboratory

BACKGROUND

Legionella pneumophila (L. pneumophila) is responsible for 96% of Legionnaires' disease (LD) and 10% of all worldwide pneumonia cases. Legiolert™, a liquid culture method for most probable number (MPN) enumeration of L. pneumophila, was developed by IDEXX Laboratories. The method detects all serogroups of L. pneumophila in potable and non-potable water samples.

OBJECTIVE

The goal of this study is to establish that Legiolert is a suitable alternative method to meet testing requirements in Spain for the enumeration of Legionella in water samples.

METHODOLOGY

The laboratory analyzed 118 environmental water samples from the Barcelona region (56 potable and 62 non-potable) in parallel by the Standard method for detection and enumeration of Legionella (ISO 11731:1998) and by Legiolert. Comparison of the recovery of the alternative method (Legiolert) and the Standard was made using ISO 17994:2014 and McNemar's binomial test statistical methods.

RESULTS

44 samples were positive for Legionella (36 potable and 8 non-potable). Legiolert and the Standard method detected a similar percentage of positive samples, with Legiolert being slightly higher (31 vs 30%) and detecting higher concentrations of Legionella within the samples. ISO 17994:2014 analysis of the potable water samples found Legiolert was more sensitive than the Standard at detecting Legionella, even when complete Legionella species (L. spp.) results were considered for both methods. The two methods also demonstrated equivalent detection of L. spp. according to the McNemar's test. The comparison is significantly more in favor of Legiolert when only L. pneumophila results are considered. Each confirmation run with material extracted from positive Legiolert wells contained L. pneumophila, giving the method a specificity of 100%. Although statistical results for non-potable waters are not included because of the low number of samples, the two methods trended towards equivalence.

CONCLUSIONS

Relative to the Standard method, Legiolert has a greater sensitivity and selectivity, and appears to have higher recovery for L. pneumophila, and equivalent recovery when L. spp. is included in the comparison. Legiolert also has high specificity. The procedural advantages of Legiolert allow laboratories to save on resources, costs, and time and consequently to test more frequently. In conclusion, the study finds IDEXX Legiolert a suitable alternative to ISO 11731:1998.