The impact of aerators on water contamination by emerging gram-negative opportunists in at-risk hospital departments

A meta-analysis of Legionella pneumophila contamination in hospital water systems

BACKGROUND

Legionella pneumophila is a common cause of community-acquired pneumonia. We aimed to determine the pooled rates of L pneumophila contamination in the water environment of the hospital.

METHODS

We searched PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure, WangFang and Science Direct, The Cochrane Library, and Science Finder, for relevant studies published until December 2022. Stata 16.0 software was used to determine pooled contamination rates, publication bias, and subgroup analysis.

RESULTS

Forty-eight eligible articles with a total of 23,640 samples of water were evaluated, and the prevalence of L pneumophila was 41.6%. The results of the subgroup analysis showed that the pollution rate of L pneumophila in hot water (47.6%) was higher than that in other water bodies. The rates of L pneumophila contamination were higher in developed countries (45.2%), culture methods (42.3%), published between 1985 and 2015 (42.9%), and studies with a sample size of less than 100 (53.0%).

CONCLUSIONS

L pneumophila contamination in medical institutions is still very serious and should be paid attention to, especially in developed countries and hot water tanks.

Altering Microbiomes with Hydroxyapatite Nanoparticles: A Metagenomic Analysis

Hydroxyapatite (HAp), the most abundant biological material among mammals, has been recently demonstrated to possess moderate antibacterial properties. Metagenomics provides a series of tools for analyzing the simultaneous interaction of materials with larger communities of microbes, which may aid in optimizing the antibacterial activity of a material such as HAp. Here, a microbiome intrinsic to the sample of sandy soil collected from the base of an African Natal plum (Carissa macrocarpa) shrub surrounding the children's sandbox at the Arrowhead Park in Irvine, California was challenged with HAp nanoparticles and analyzed with next-generation sequencing for hypervariable 16S ribosomal DNA base pair homologies. HAp nanoparticles overwhelmingly reduced the presence of Gram-negative phyla, classes, orders, families, genera and species, and consequently elevated the relative presence of their Gram-positive counterparts. Thermodynamic, electrostatic and chemical bonding arguments were combined in a model proposed to explain this selective affinity. The ability of amphiphilic surface protrusions of lipoteichoic acid in Gram-positive bacteria and mycolic acid in mycobacteria to increase the dispersibility of the bacterial cells and assist in their resistance to capture by the solid phase is highlighted. Within the Gram-negative group, the variability of the distal, O-antigen portion of the membrane lipopolysaccharide was shown to be excessive and the variability of its proximal, lipid A portion insufficient to explain the selectivity based on chemical sequence arguments. Instead, flagella-driven motility proves to be a factor favoring the evasion of binding to HAp. HAp displayed a preference toward binding to less pathogenic bacteria than those causative of disease in humans, while taxa having a positive agricultural effect were largely captured by HAp, indicating an evolutionary advantage this may have given it as a biological material. The capacity to selectively sequester Gram-negative microorganisms and correspondingly alter the composition of the microbiome may open up a new avenue in environmental and biomedical applications of HAp.

Evaluation of Multidrug-Resistant P. aeruginosa in Healthcare Facility Water Systems

According to the WHO, P. aeruginosa is one of the antibiotic-resistant bacteria that represent the biggest threat to public health. The aim of the study was to establish the prevalence of antibiotic-resistant P. aeruginosa in the water systems of various healthcare facilities over the course of nine years. A total of 4500 tap water system samples were taken from seventeen healthcare facilities. The culture method was used to detect P. aeruginosa, and the isolates were then tested for antibiotic resistance using the standardised disc diffusion method. Eleven antibiotics from five different classes were tested. P. aeruginosa was found to have contaminated 2.07% (no. 93) of the water samples. The majority of positive samples came from the dental units (30.11%) and the ward kitchens (23.66%). Considering the total isolates, 56.99% (no. 3) were resistant to at least one of the antibiotics tested. A total of 71.43% of P. aeruginosa isolated from water emerging from dental unit handpieces was antibiotic-resistant, with 45% of it resistant to ≥3 classes of antibiotics. Out of the total isolates, 19.35% showed resistance to carbapenems. It would be advisable to systematically screen tap water for opportunistic micro-organisms such as P. aeruginosa, as many countries already do, including this in the Water Safety Plan.

Are pathogenic Legionella non-pneumophila a common bacteria in Water Distribution Networks?

The present study analyzes at the national level, the presence of circulating Legionella in the artificial aquatic systems of different facilities of all of them state-owned centers throughout Spain for 12 months. 1754 water samples from various state-owned centers were collected from January to December 2014. Samples were collected from the cooling towers and evaporative condensers (CTC), and water distribution networks such as domestic hot water (DHW), cold water for human consumption (CW), sprinkler irrigation systems (SIS), fire sprinkler systems (FSS), and water from decorative fountains (DF). All these facilities are considered, according to current regulations, as potential amplifying systems for bacteria and possible sources of infection by the generation of droplets and aerosols. The isolation and counting of Legionella in water samples was carried out using microbiological culture following the international normative UNE-EN-ISO 11,731:2007 (ISO 11,731:1998) and UNE-EN ISO 8199:2008 (ISO 8199:2005).The quantification of Legionella colonization, the annual distribution, and the geographical distribution of the Legionella isolates recovered in the water were analyzed. Besides, molecular techniques were used for the characterization of the Legionella non-pneumophila isolates. Legionella was recovered from 15.79% of the analyzed water samples. High colonization was more frequently detected in water samples from CTC, DHW, CW, and DF. Regarding the geographic distribution, positive samples of Legionella were obtained in 14 of the 18 Spanish locations analyzed. Legionella non-pneumophila was the most prevalent and was isolated from water samples from 13 different geographical locations (72%). Legionella anisa and Legionella jordanis were the most frequently non-pneumophila species isolated. Legionella donaldsonii was isolated for the first time in the water distribution networks in Spain. Legionella pneumophila sg 2-14 was detected in 13 locations and Legionella pneumophila sg 1 in 11 locations. Therefore, our study concludes that the presence of Legionella pneumophila and Legionella non-pneumophila species in these systems can be a potential threat to public health and should be examined thoroughly with complementary techniques, such as molecular techniques as a screen for routine diagnosis.

The role of the faucet's aerator kit for contamination of drinking water

Experimentally we demonstrated the possibility of retrograde contamination of aerator kits, independent of special design, with Pseudomonas aeruginosa. In a real life setting contamination of aerator kits with typical environmental and water organisms occurred, whether they were changed after 6 or 12 weeks, so we recommend a risk adjusted rather than schedule-based changing regimen in hospitals, eg, if potential retrograde contamination might be a relevant factor in rooms occupied by patients with multiresistant gram-negative organisms.

Evaluation of Recommended Water Sample Collection Methods and the Impact of Holding Time on Legionella Recovery and Variability from Healthcare Building Water Systems

Water safety and management programs (WSMP) utilize field measurements to evaluate control limits and monitor water quality parameters including Legionella presence. This monitoring is important to verify that the plan is being implemented properly. However, once it has been determined when and how to sample for Legionella, it is important to choose appropriate collection and processing methods. We sought to compare processing immediate and flushed samples, filtration of different volumes collected, and sample hold times. Hot water samples were collected immediately and after a 2-min flush. These samples were plated directly and after filtration of either 100 mL, 200 mL, or 1 L. Additionally, unflushed samples were collected and processed immediately and after 1, 24, and 48 h of hold time. We found that flushed samples had significant reductions in Legionella counts compared to immediate samples. Processing 100 mL of that immediate sample both directly and after filter concentration yielded the highest concentration and percent sample positivity, respectively. We also show that there was no difference in culture values from time 0 compared to hold times of 1 h and 24 h. At 48 h, there were slightly fewer Legionella recovered than at time 0. However, Legionella counts were so variable based on sampling location and date that this hold time effect was minimal. The interpretation of Legionella culture results depends on the sample collection and processing methods used, as these can have a huge impact on the success of sampling and the validation of control measures.

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

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.

A microbiological survey of handwashing sinks in the hospital built environment reveals differences in patient room and healthcare personnel sinks

Handwashing sinks and their associated premise plumbing are an ideal environment for pathogen-harboring biofilms to grow and spread throughout facilities due to the connected system of wastewater plumbing. This study was designed to understand the distribution of pathogens and antibiotic resistant organisms (ARO) within and among handwashing sinks in healthcare settings, using culture-dependent methods to quantify Pseudomonas aeruginosa, opportunistic pathogens capable of growth on a cefotaxime-containing medium (OPP-C), and carbapenem-resistant Enterobacteriaceae (CRE). Isolates from each medium identified as P. aeruginosa or Enterobacteriaceae were tested for susceptibility to aztreonam, ceftazidime, and meropenem; Enterobacteriaceae were also tested against ertapenem and cefotaxime. Isolates exhibiting resistance or intermediate resistance were designated ARO. Pathogens were quantified at different locations within handwashing sinks and compared in quantity and distribution between healthcare personnel (HCP) and patient room (PR) sinks. ARO were compared between samples within a sink (biofilm vs planktonic samples) and between sink types (HCP vs. PR). The drain cover was identified as a reservoir within multiple sinks that was often colonized by pathogens despite daily sink cleaning. P. aeruginosa and OPP-C mean log₁₀ CFU/cm² counts were higher in p-trap and tail pipe biofilm samples from HCP compared to PR sinks (2.77  ± 2.39 vs. 1.23 ± 1.62 and 5.27 ± 1.10 vs. 4.74 ± 1.06) for P. aeruginosa and OPP-C, respectively. P. aeruginosa and OPP-C mean log₁₀ CFU/ml counts were also higher (p < 0.05) in HCP compared to PR sinks p-trap water (2.21 ± 1.52 vs. 0.89 ± 1.44 and 3.87 ± 0.78 vs. 3.21 ± 1.11) for P. aeruginosa and OPP-C, respectively. However, a greater percentage of ARO were recovered from PR sinks compared to HCP sinks (p < 0.05) for Enterobacteriaceae (76.4 vs. 32.9%) and P. aeruginosa (25.6 vs. 0.3%). This study supports previous work citing that handwashing sinks are reservoirs for pathogens and ARO and identifies differences in pathogen and ARO quantities between HCP and PR sinks, despite the interconnected premise plumbing.

Public Health Risks Associated with Heavy Metal and Microbial Contamination of Drinking Water in Australia

Recently in Australia concerns have been raised regarding the contamination of municipal drinking water supplies with lead. This is of particular concern to children due to the impact of lead exposure on cognitive development and as such these findings have received much media attention. The response from legislators has been swift, and The Victorian School Building Authority has announced that all new schools and school upgrade works will only use lead-free tapware and piping systems. However, while the immediate replacement of lead-containing brass fittings may seem a logical and obvious response, it does not consider the potential implications on microbial contamination. This is particularly concerning given the increasing public health threat posed by opportunistic premise plumbing pathogens (OPPPs). This commentary explores this public health risk of lead exposure from plumbing materials compared to the potential public health risks from OPPPs. Non-tuberculous mycobacterium was chosen as the example OPPP, and the influence on plumbing material and its public health burden in Australia is explored. This commentary highlights the need for future research into the influence of plumbing material on OPPPs prior to any changes in legislation regarding plumbing material.

Legionella pneumophila levels and sequence-type distribution in hospital hot water samples from faucets to connecting pipes

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 upflow 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, 1 h) 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.

Role of hot water temperature and water system use on Legionella control in a tertiary hospital: An 8-year longitudinal study

Although measures to minimize Legionella colonization in sanitary hot water installations are well established, there is little evidence of their long-term effectiveness in hospital buildings. During an 8-year period, hot water in a large hospital building was sampled monthly in areas with suitable dimensioning and recirculation and in areas with dead legs and low-use taps. In the former areas, the percentage of Legionella-negative samples was 83.2% when the temperature was ≥55%, 64.9% when between 50.1 °C and 54.0 °C, and 51.6% when ≤50 °C (p for trend <0.001). In the highest temperature group, no samples with ≥10³ cfu/L were observed. In poorly designed areas, only 44.7% of samples were negative, and 28.9% presented ≥10³ cfu/L although reaching 55 °C. In these areas, multivariate analysis showed that if hot water supplies were not used daily, the risk of Legionella colonization was greater than two-fold (odds ratio: 2.84; 95% confidence interval: 1.26-6.41), and the risk of finding Legionella concentrations ≥10³ cfu/L was more than three-fold (odds ratio: 3.18; 95% confidence interval: 1.36-7.46), regardless the temperature. These findings indicate that the effectiveness of maintaining sanitary hot water at a minimum temperature of 55 °C is significantly better than that at 50 °C for the environmental control of Legionella but only in installations with suitable dimensioning and recirculation. In installations that do not meet these conditions, high temperatures alone result in insufficient control.

Impact of stagnation and sampling volume on water microbial quality monitoring in large buildings

Microbial drinking water quality can be altered in large buildings, especially after stagnation. In this study, bacterial profiles were generated according to the stagnation time and the volume of water collected at the tap. Successive volumes of cold and hot water were sampled after controlled stagnation periods. Bacterial profiles revealed an important decline (> 2 log) in culturable cells in the first 500 mL sampled from the hot and cold water systems, with a steep decline in the first 15 mL. The strong exponential correlation (R² ≥ 0.97) between the culturable cell counts in water and the pipe surface-to-volume ratio suggests the biofilm as the main contributor to the rapid increase in suspended culturable cells measured after a short stagnation of one-hour. Results evidence the contribution of the high surface-to-volume ratio at the point of use and the impact of short stagnation times on the increased bacterial load observed. Simple faucets with minimal internal surface area should be preferred to minimize surface area. Sampling protocol, including sampling volume and prior stagnation, was also shown to impact the resulting culturable cell concentration by more than 1000-fold. Sampling a smaller volume on first draw after stagnation will help maximize recovery of bacteria.

Presence of Legionella spp. in Hot Water Networks of Different Italian Residential Buildings: A Three-Year Survey

Although the European reports highlight an increase in community-acquired Legionnaires’ disease cases, the risk of Legionella spp. in private houses is underestimated. In Pisa (Italy) we performed a three-year survey on Legionella presence in 121 buildings with an independent hot water production (IB); 64 buildings with a central hot water production (CB); and 35 buildings with a solar thermal system for hot water production (TB). From all the 220 buildings Legionella spp. was researched in two hot water samples collected either at the recirculation point or on the first floor and on the last floor, while the potable water quality was analysed in three cold water samples collected at the inlet from the aqueduct network, at the exit from the autoclave, and at the most remote tap. Legionella pneumophila sg1, Legionella pneumophila sg2–16, and non-pneumophila Legionella species were detected in 26% of the hot water networks, mostly in CB and TB. In these buildings we detected correlations between the presence of Legionella and the total chlorine concentration decrease and/or the increase of the temperature. Cold water resulted free from microbiological hazards, with the exception of Serratia liquefaciens and Enterobacter cloacae isolated at the exit from two different autoclaves. We observed an increase in total microbial counts at 22 °C and 37 °C between the samples collected at the most remote taps compared to the ones collected at the inlet from the aqueduct. The study highlights a condition of potential risk for susceptible categories of population and supports the need for measures of risk assessment and control.

Application of Hydrogen Peroxide as an Innovative Method of Treatment for Legionella Control in a Hospital Water Network

Objectives: To evaluate the effectiveness of hydrogen peroxide (HP) use as a disinfectant in the hospital water network for the control of Legionella spp. colonization. Methods: Following the detection of high levels of Legionella contamination in a 136-bed general hospital water network, an HP treatment of the hot water supply (25 mg/L) was adopted. During a period of 34 months, the effectiveness of HP on Legionella colonization was assessed. Legionella was isolated in accordance with ISO-11731 and identification was carried out by sequencing of the mip gene. Results: Before HP treatment, L. pneumophila sg 2–15 was isolated in all sites with a mean count of 9950 ± 8279 cfu/L. After one-month of HP treatment, we observed the disappearance of L. pneumophila 2–15, however other Legionella species previously not seen were found; Legionellapneumophila 1 was isolated in one out of four sampling sites (2000 cfu/L) and other non-pneumophila species were present in all sites (mean load 3000 ± 2887 cfu/L). Starting from September 2013, HP treatment was modified by adding food-grade polyphosphates, and in the following months, we observed a progressive reduction of the mean load of all species (p < 0.05), resulting in substantial disappearance of Legionella colonization. Conclusion: Hydrogen peroxide demonstrated good efficacy in controlling Legionella. Although in the initial phases of treatment it appeared unable to eliminate all Legionella species, by maintaining HP levels at 25 mg/L and adding food-grade polyphosphates, a progressive and complete control of colonization was obtained.

Annual variations and effects of temperature on Legionella spp. and other potential opportunistic pathogens in a bathroom

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.

Experimental comparison of point-of-use filters for drinking water ultrafiltration

BACKGROUND

Waterborne pathogens such as Pseudomonas spp. and Legionella spp. may persist in hospital water networks despite chemical disinfection. Point-of-use filtration represents a physical control measure that can be applied in high-risk areas to contain the exposure to such pathogens. New technologies have enabled an extension of filters' lifetimes and have made available faucet hollow-fibre filters for water ultrafiltration.

AIM

To compare point-of-use filters applied to cold water within their period of validity.

METHODS

Faucet hollow-fibre filters (filter A), shower hollow-fibre filters (filter B) and faucet membrane filters (filter C) were contaminated in two different sets of tests with standard bacterial strains (Pseudomonas aeruginosa DSM 939 and Brevundimonas diminuta ATCC 19146) and installed at points-of-use. Every day, from each faucet, 100 L of water was flushed. Before and after flushing, 250 mL of water was collected and analysed for microbiology.

FINDINGS

There was a high capacity of microbial retention from filter C; filter B released only low Brevundimonas spp. counts; filter A showed poor retention of both micro-organisms.

CONCLUSION

Hollow-fibre filters did not show good micro-organism retention. All point-of-use filters require an appropriate maintenance of structural parameters to ensure their efficiency.

Pseudomonas aeruginosa in premise plumbing of large buildings

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that is widely occurring in the environment and is recognized for its capacity to form or join biofilms. The present review consolidates current knowledge on P. aeruginosa ecology and its implication in healthcare facilities premise plumbing. The adaptability of P. aeruginosa and its capacity to integrate the biofilm from the faucet and the drain highlight the role premise plumbing devices can play in promoting growth and persistence. A meta‐analysis of P. aeruginosa prevalence in faucets (manual and electronic) and drains reveals the large variation in device positivity reported and suggest the high variability in the sampling approach and context as the main reason for this variation. The effects of the operating conditions that prevail within water distribution systems (disinfection, temperature, and hydraulic regime) on the persistence of P. aeruginosa are summarized. As a result from the review, recommendations for proactive control measures of water contamination by P. aeruginosa are presented. A better understanding of the ecology of P. aeruginosa and key influencing factors in premise plumbing are essential to identify culprit areas and implement effective control measures.

Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain

Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila.

Impact of electronic faucets and water quality on the occurrence of Pseudomonas aeruginosa in water: a multi-hospital study

OBJECTIVE

To compare Pseudomonas aeruginosa prevalence in electronic and manual faucets and assess the influence of connecting pipes and water quality.

SETTING

Faucets in 4 healthcare centers in Quebec, Canada.

METHODS

Water samples from 105 electronic, 90 manual, and 14 foot-operated faucets were analyzed for P. aeruginosa by culture and enzymatic detection, and swab samples from drains and aerators were analyzed by culture. Copper and residual chlorine concentrations, temperature, and flow rate were measured. P. aeruginosa concentrations were analyzed in 4 consecutive volumes of cold water and a laboratory study was conducted on copper pipes and flexible hoses.

RESULTS

P. aeruginosa contamination was found in drains more frequently (51%) than in aerators (1%) or water (culture: 4%, enzyme detection: 16%). Prevalence in water samples was comparable between manual (14%) and 2 types of electronic faucets (16%) while higher for foot-operated faucets (29%). However, type 2 electronic faucets were more often contaminated (31%) than type 1 (14%), suggesting that faucet architecture and mitigated volume (30 mL vs 10 mL) influence P. aeruginosa growth. Concentrations were 100 times higher in the first 250 mL than after flushing. Flexible hoses were more favorable to P. aeruginosa growth than copper and a temperature of 40°C led to higher counts.

CONCLUSIONS

The types of faucets and connecting pipes, flow rate, and water quality are important parameters influencing the prevalence and the concentrations of P. aeruginosa in faucets. High concentrations of P. aeruginosa in the first 250 mL suggest increased risk of exposure when using the first flush.

Post-Outbreak Investigation of Pseudomonas aeruginosa Faucet Contamination by Quantitative Polymerase Chain Reaction and Environmental Factors Affecting Positivity

OBJECTIVE

To perform a post-outbreak prospective study of the Pseudomonas aeruginosa contamination at the faucets (water, aerator and drain) by culture and quantitative polymerase chain reaction (qPCR) and to assess environmental factors influencing occurrence

SETTING

A 450-bed pediatric university hospital in Montreal, Canada

METHODS

Water, aerator swab, and drain swab samples were collected from faucets and analyzed by culture and qPCR for the post-outbreak investigation. Water microbial and physicochemical parameters were measured, and a detailed characterization of the sink environmental and design parameters was performed.

RESULTS

The outbreak genotyping investigation identified drains and aerators as the source of infection. The implementation of corrective measures was effective, but post-outbreak sampling using qPCR revealed 50% positivity for P. aeruginosa remaining in the water compared with 7% by culture. P. aeruginosa was recovered in the water, the aerator, and the drain in 21% of sinks. Drain alignment vs the faucet and water microbial quality were significant factors associated with water positivity, whereas P. aeruginosa load in the water was an average of 2 log higher for faucets with a positive aerator.

CONCLUSIONS

P. aeruginosa contamination in various components of sink environments was still detected several years after the resolution of an outbreak in a pediatric university hospital. Although contamination is often not detectable in water samples by culture, P. aeruginosa is present and can recover its culturability under favorable conditions. The importance of having clear maintenance protocols for water systems, including the drainage components, is highlighted.

Infect. Control Hosp. Epidemiol. 2015;36(11):1283–1291

Temperature diagnostic to identify high risk areas and optimize Legionella pneumophila surveillance in hot water distribution systems

Legionella pneumophila is frequently detected in hot water distribution systems and thermal control is a common measure implemented by health care facilities. A risk assessment based on water temperature profiling and temperature distribution within the network is proposed, to guide effective monitoring strategies and allow the identification of high risk areas. Temperature and heat loss at control points (water heater, recirculation, representative points-of-use) were monitored in various sections of five health care facilities hot water distribution systems and results used to develop a temperature-based risk assessment tool. Detailed investigations show that defective return valves in faucets can cause widespread temperature losses because of hot and cold water mixing. Systems in which water temperature coming out of the water heaters was kept consistently above 60 °C and maintained above 55 °C across the network were negative for Legionella by culture or qPCR. For systems not meeting these temperature criteria, risk areas for L. pneumophila were identified using temperature profiling and system's characterization; higher risk was confirmed by more frequent microbiological detection by culture and qPCR. Results confirmed that maintaining sufficiently high temperatures within hot water distribution systems suppressed L. pneumophila culturability. However, the risk remains as shown by the persistence of L. pneumophila by qPCR.

A rapid culture independent methodology to quantitatively detect and identify common human bacterial pathogens associated with contaminated high purity water

Background

Water and High Purity Water (HPW) distribution systems can be contaminated with human pathogenic microorganisms. This biocontamination may pose a risk to human health as HPW is commonly used in the industrial, pharmaceutical and clinical sectors. Currently, routine microbiological testing of HPW is performed using slow and labour intensive traditional microbiological based techniques. There is a need to develop a rapid culture independent methodology to quantitatively detect and identify biocontamination associated with HPW.

Results

A novel internally controlled 5-plex real-time PCR Nucleic Acid Diagnostics assay (NAD), was designed and optimised in accordance with Minimum Information for Publication of Quantitative Real-Time PCR Experiments guidelines, to rapidly detect, identify and quantify the human pathogenic bacteria Stenotrophomonas maltophilia, Burkholderia species, Pseudomonas aeruginosa and Serratia marcescens which are commonly associated with the biocontamination of water and water distribution systems. The specificity of the 5-plex assay was tested against genomic DNA isolated from a panel of 95 microorganisms with no cross reactivity observed. The analytical sensitivities of the S. maltophilia, B. cepacia, P. aeruginosa and the S. marcescens assays are 8.5, 5.7, 3.2 and 7.4 genome equivalents respectively.

Subsequently, an analysis of HPW supplied by a Millipore Elix 35 water purification unit performed using standard microbiological methods revealed high levels of naturally occurring microbiological contamination. Five litre water samples from this HPW delivery system were also filtered and genomic DNA was purified directly from these filters. These DNA samples were then tested using the developed multiplex real-time PCR NAD assay and despite the high background microbiological contamination observed, both S. maltophilia and Burkholderia species were quantitatively detected and identified. At both sampling points the levels of both S. maltophilia and Burkholderia species present was above the threshold of 10 cfu/100 ml recommended by both EU and US guidelines.

Conclusions

The novel culture independent methodology described in this study allows for rapid (<5 h), quantitative detection and identification of these four human pathogens from biocontaminated water and HPW distribution systems. We propose that the described NAD assay and associated methodology could be applied to routine testing of water and HPW distribution systems to assure microbiological safety and high water quality standards.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-015-0124-1) contains supplementary material, which is available to authorized users.

Hospital water and opportunities for infection prevention

Nosocomial waterborne pathogens may reach patients through several modes of transmission. Colonization of healthcare facility waterworks can occur in the proximal infrastructure, in the distal water outlets, or both. Infections with waterborne organisms such as Legionella, mycobacteria, Pseudomonas, and others cause significant morbidity and mortality, particularly in immunocompromised patients. Hospitals should have prospective water safety plans that include preventive measures, as prevention is preferable to remediation of contaminated hospital water distribution systems. Whole-genome sequencing may provide more informative epidemiologic data to link patient infections with hospital water isolates.