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Potable Water Systems in Health Care Facilities

Background, Facts and Solutions for Water Management Programs

What happens to drinking water from its origin to the tap?

 

In most circumstances, well-controlled, hygienic water is delivered from water plants to cities. During transport, water is cold and flows continuously through large diameter pipes. However, this situation frequently changes at the point-of- entrance to buildings (1,2). Within buildings water can stagnate and its temperature increase. It passes through complex internal distribution systems consisting of narrow pipes
with possibly corroded inner surfaces and dead ends. This environment can provide optimal conditions for the formation of biofilm from which bacteria and other microorganisms may be continuously released into the water (3-6).   

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Image 1: Drinking water is derived from lakes, rivers or deep underground. It is purified in water plants and transported underground in large diameter pipes to cities and buildings, where it then often runs through small diameter pipes and may stagnate and warm up. These conditions are ideal for biofilm formation.

What is biofilm and how does it develop?

 

In water distribution systems biofilm can develop within a few days even if the water meets drinking water criteria (2). Biofilm can host bacteria, amoeba, algae and other microorganisms. Under low flow conditions, such as in dead legs, particularly thick biofilms can form. Under the force of waterflow biofilm can shear off and biofilm particles can colonize other parts of the water distribution system (3). External stress in the pipework, such as disinfection measures, can result in an increased expression of the biofilm phenotype cell which is responsible for the strong attachment of cells to a surface (5). 

Image 2: Biofilm establishes in several phases over a few days. It contains microorganisms within its slimy matrix. With increasing thickness, biofilm particles containing large amounts of bacteria are released into the water stream.

Biofilm influences water quality

Why does biofilm influence the water quality?

 

Biofilm protects the microorganisms within from chemical agents and thermal disinfection procedures (2,5). It is extremely difficult to completely eradicate the biofilm community once established. Irregular shedding from a biofilm can result in significant deviations of bacterial counts at sampling sites or points-of-use (POU) (2-4). Bacteria within biofilm communities have been shown to exhibit greater resistance against antimicrobial treatments than corresponding planktonic cells (3). 

Image 3: When biofilm loaded with bacteria is released into the water stream, high microbial counts may be measured at the outlets. Annual testing provides only a snapshot of information, while regular testing is useful to monitor the bacterial risk of a pipe network. 

Which micro- organisms can be found inside biofilms?

 

The majority of bacteria in a water pipework live within biofilm (about 95 %) and only about 5 % occur in
the water phase (7). Biofilms contain a large variety of waterborne microorganisms (91-93). These may include protozoa (e.g. Acanthamoeba), fungi (e.g. Aspergillus spp., Fusarium spp.), viruses and a number of human pathogenic bacteria (1,3,5,7-9). Among those bacterial species found in biofilm that are potentially harmful for immunocompromised people are Pseudomonas aeruginosa, non-tuberculous Mycobacteria, Stenotrophomonas maltophilia, Acinetobacter baumanii, Chrysobacterium spp., Sphingomonas spp., Aeromonas hydrophila, Simkania negevensis, Elizabethkingia meningoseptica and Klebsiella spp. (3,5,7,10-13). Legionella pneumophila is perhaps the best-known waterborne bacterium colonizing biofilm, and it can be found in both central storage areas (e.g. water tanks) as well as peripheral water outlets (2,3,5). Pseudomonas aeruginosa is known to be a major cause of severe infections (14-17), including pneumonia, sepsis, wound and skin infections. 

Image 4: Biofilm in water networks may contain a large variety of microorganisms such as fungi (e.g. Aspergillus spp., left), rod-shaped bacteria (e.g. Legionella spp., middle) and protozoa (e.g. amoeba, right). 

Viable but non-culturable

What are Viable But Non-Culturable cells?

 

The Viable But Non-Culturable (VBNC) cell fails to grow on routine bacteriological culture media, but is alive and capable of metabolic activity - indeed it can be “resuscitated” to a culturable state with renewed virulence (6, 18-21). This discovery has thrown the accuracy of quantifying culturing techniques into question. It is understood that a high proportion of biofilm dwelling cells live in the VBNC state and that the VBNC state can be induced by antibacterial material such as copper pipes (19), stress factors like starvation, exposure to temperatures outside the range of growth or exposure to chemical and thermal treatments (20-26). As water pathogens such as P. aeruginosa and L. pneumophila in their VBNC state are not detectable by standard culture methods, alternative diagnostic technologies such as Polymerase Chain Reaction (PCR), Fluorescence In Situ Hybridization (FISH) or determination of total cell number (TCN) are required in order to confirm their presence (6, 27). L. pneumophila, P. aeruginosa, Campylobacter jejuni and other waterborne bacteria have also been shown to be resuscitated to culturable cells under suitable stimuli (21, 28, 29). 

Image 5: VBNC cells cannot be detected by classical culture methods. 

What role do amoeba play in the biofilm community?

 

Amoeba are very important hosts for water bacteria. L. pneumophila, Mycobacteria spp. and other “amoeba resistant bacteria” can be carried by these protozoa (9, 30-34). Legionellae are taken up into amoeba without being digested and replicate there within vacuoles. When the Legionellae have reached a certain density, the vacuoles release them into the water system (31). Amoeba not only function as environmental reservoirs for Legionella, but have been also shown to be involved in selecting for, protecting and maintaining potentially pathogenic Legionella spp. in the environment (35, 36). 

Image 6: Amoeba can incorporate Legionella which then proliferate inside vacuoles and are later released, either in the form of planktonic, free living bacteria, or packed within vacuoles. 

Transmission Pathways

Why is Pseudomonas aeruginosa of particular concern?

 

Pseudomonas aeruginosa is widely reported as one of the most common and problematic bacteria in health care facilities (15, 37). Several studies have shown that up to 50% of hospital acquired P. aeruginosa infections may be derived from the water distribution system (15, 17, 38-44, 48). 

Image 7: Pseudomonas aeruginosa is an aerobic bacterial species and commonly found at the periphery of water systems such as taps, showers or sinks. 

What are the possible infection pathways from water points-of-use to patients?

 

Inhalation and aspiration represent the established transmission pathways for Legionella spp. (49), whereas Pseudomonas spp. is reported to be mainly transmitted by contact and aspiration (17, 41). During daily routines, tap water is used for personal hygiene. For example, in the healthcare environment, due to the severity of their disease states, ICU patients often have multiple access devices such as catheters, drains and tracheal tubes. These portals represent potential entrance sites for bacteria from numerous sources. Droplets of contaminated tap water or contaminated hands of healthcare professionals can inadvertently come into contact with those entrance sites (50). Rogues et al. reported that 14 % of ICU healthcare professionals hands were Pseudomonas positive when washed with contaminated tap water and 12 % were positive when the last contact was with a Pseudomonas positive patient (41). Contaminated bottled water or contaminated water from drinking water dispensers has also been described as a source of Pseudomonas bacteria (51-53). 

Image 8: Water for wound care, or the patient’s personal hygiene, may contain bacteria resulting in patient colonization and infection. A patient may not necessarily have to use a water outlet to become colonized; immobilized patients, e.g. within ICUs, can come in contact with contaminated water brought by health care workers to the patient’s bed. 

Point-of-Use water filtration

Why is complete biofilm eradication by systemic treatments so difficult?

 

Water distribution systems in large buildings are frequently complex networks and can be up to 50 km in length. Dead ends, corroded pipes, low throughput, insuf cient temperature below 131 °F (55 °C) in the hot water pipes and above 68 °F (20 °C) in the cold pipes contribute to biofilm formation and impede eradication of biofilm (54). Heat & Flush procedures (e.g. 10-20 minutes of simultaneous  flushing of all outlets with water heated to > 158 °F (> 70 °C) may have only short term effects (55). Legionella strains may even become heat resistant after thermal treatment over a long time (20). Moreover, the thermophilic Legionella community, including L. pneumophila, is able to grow in hot water system above 122 °F (50 °C) (56). Thermal procedures can result in warming up cold water (26, 57, 58), when both hot and cold water pipes are located in the same duct increasing the risk of biofilm in cold water. Chemical treatments are bactericidal to free floating bacteria but have limited effects on biofilm and may create hazardous byproducts during use (10, 55, 59, 60). Therefore, areas with vulnerable users may require additional protection (e.g. 0.2 μm point-of-use waterfiltration) to minimize risk of transmission of waterborne pathogens. 

Image 9: Water systems in hospitals can contain corroded pipes and dead ends which cannot be reached by systemic disinfection. Bacteria can be released to recolonize the system after disinfection. Construction work may also cause bio lm release into the network. 

Where are point-of-use (POU) water filters (tap filter, shower filter) typically used?

 

Point-of-use water filters can be used as an additional control measure in those areas where immunocompromised people may come into contact with water (61-85), in outbreak and critical contamination solutions as an aid in reducing patient exposure. They can be exibly installed at faucets (tap filters) or connected to shower hoses (shower filters). In medical facilities the most common areas for POU water filter installation are bone marrow transplant units, hematology/oncology units, ICUs, transplantation units, burn units, neonatology, endoscopic reprocessing, birthing pools, kitchen (for food preparation and drinking water provision), and geriatric departments. POU water filtration is also increasingly used in nursing homes or home care settings POU filters are quickly installed which makes them an effective and immediate management tool in acute water contamination situations. 

Image 10: Point-of-use water filters can be installed at taps, showers or in-line applications in various health care settings, such as hospitals, day surgery units, dental practices, dialysis units, or rehabilitation centers. 

User Requirements for Water Filters

What are the user requirements for POU water filtration?

 

User facilities typically ask for POU filtration designed to deliver water quality in accordance with international standards for sterilizing grade filtration (complete retention of ≥107 CFU Brevundimonas diminuta/cm2 effective filtration area) (87-90). End point filters are mostly used in humid environments, and the risk of contamination of the filter housing exists through backsplash. In order to minimize this risk of retrograde contamination, Pall POU water filters contain anti-retrograde contamination technologies. Hygienic performance of these POU filters has been demonstrated through laboratory validation, multicentre field evaluations, and independent clinical studies demonstrating robust performance over the full product lifetime (61-85). 

Image 11: F.e. the QPoint® Tap and Shower Assemblies consist of a permanent chrome docking station and a disposable, recyclable filter capsule for up to 62 days use. Advanced prefiltration technology improves ow rates throughout the filter capsule lifetime. An inner shield protects from direct back splash into the inner parts of the filter capsule.

Are there studies on POU water filtration?

Numerous reports have demonstrated the high efficiency of Pall’s POU water filters in the retention of microoganisms from water outlets in clinical locations and conditions (17, 28-49, 61-86). 

Pall-Aquasafe™ Disposable Water Filters

The Pall-Aquasafe Disposable Water Filters (AQF4A, AQ31F1SA, AQ31F1RA, AQINA) provide filtered water suitable for washing and drinking, superficial wound cleansing, cleaning of equipment used in medical procedures and washing of surgeon's hands for up to 31 day use. The double layer sterilizing grade Supor® membrane is rated and validated at 0.2 μm, and may aid in infection control by acting as a barrier to waterborne particulates and pathogens.
The Pall-Aquasafe Disposable Water Filters (AQF4A, AQ31F1SA, AQ31F1RA, AQINA) provide filtered water suitable for washing and drinking, superficial wound cleansing, cleaning of equipment used in medical procedures and washing of surgeon's hands for up to 31 day use. The double layer sterilizing grade Supor® membrane is rated and validated at 0.2 μm, and may aid in infection control by acting as a barrier to waterborne particulates and pathogens.
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