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Scientific Information
Water distribution systems in large buildings such as hospitals frequently contain biofilm which is difficult to eradicate once established. Waterborne pathogenic microorganisms can be released from biofilm into the water stream. Immunocompromised patients may carry a higher infection risk for waterborne pathogens such as:
- Pseudomonas aeruginosa
- Legionella pneumophila
- Non-tuberculosis mycobacteria
- Fungi
- Other micro-organisms
Specific protective measures such as sterilizing-grade water filtration directly at the point of use are increasingly used in order to establish efficient barriers against transmission of waterborne pathogens from water sources to patients.
- What happens to drinking water from its origin to the tap?
- What is biofilm and how does it develop?
- How does biofilm influence the water quality?
- Which microorganisms can be found inside biofilms?
- What role do amoeba play in the biofilm community?
- Why is Pseudomonas aeruginosa of particular concern?
- What are the pathways for infection transmission from water sources to patients?
- Why is complete biofilm eradication by systemic treatments so difficult?
- Where are point-of-use (POU) tap and shower filters used?
- What are the requirements for POU sterile filtration?
- Are there additional advantages of Pall-Aquasafe™ sterile water filtration?
- Are there recommendations for POU filtration?
- Are there studies on infection reduction after POU filter installation?
- What economical advantages are given by POU filtration?"
- Waterborne Pathogens and Point-of-Use Filtration - Recent Developments
What happens to drinking water from its origin to the tap?
After passing several purification steps, well-controlled and hygienically safe water is delivered from water plants to communities and cities. During its transport, water is cold and flows continuously through large diameter pipes. However, this situation changes dramatically at the point of entrance to buildings1. After entering a building, water stagnates and its temperature increases. It passes through complex internal distribution systems (up to 50 km / 31 mi length) consisting of narrow pipes with possibly corroded inner surfaces and dead ends. This new environment provides optimal conditions for the formation of biofilm from which bacteria and other microorganisms are continuously released into the water2,3.
Source Water Plant User
What is biofilm and how does it develop?
Biofilm forms in places where fluids come into contact with surfaces. In water distribution systems, biofilm can develop within a few days even if the water meets drinking water criteria (< 100 CFU/mL)1. Biofilm formation starts with the adsorption of organic and inorganic particles/nutrients to the inner surface of water pipes (conditioning), followed by the attachment of bacteria that produce a sticky extracellular matrix. As the critical mass of the biofilm community increases, the biofilm shears off under the force of water flow and biofilm particles can colonize other parts of the water distribution system2. 
How does biofilm influence the water quality?
With increasing thickness the biofilm better protects the microorganisms inside from chemical agents and thermal disinfection procedures1. It is therefore extremely difficult to completely eradicate the biofilm community once it has been established. The irregular shedding from a biofilm can result in significant deviations of bacterial counts at the sampling sites or points of use (POU)1-3. Bacteria in biofilm communities have been shown to exhibit greater resistance against antimicrobial treatments than corresponding planktonic cells2.
Which microorganisms can be found inside biofilms?
Biofilms contain a large variety of waterborne microorganisms. These include protozoa (e.g. Acanthamoeba), fungi (e.g. Aspergillus spp.), viruses and a number of human pathogenic bacteria2,3. Among those bacterial species found in biofilm that are potentially harmful for immunocompromised patients, are Pseudomonas aeruginosa, nontuberculous Mycobacteria, Stenotrophomonas maltophilia, Acinetobacter baumanii, Chrysobacterium spp., Sphingomonas spp., and Klebsiella spp.2,3. Legionella pneumophila is perhaps the best-known bacterium among those that colonize in biofilm, and it can be found in both central storage areas (e.g. water tanks) as well as peripheral water outlets2,4. Pseudomonas aeruginosa is a major cause of severe infections in Intensive Care Units (ICUs) and is commonly found at peripheral sites5,6.
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 safely carried by these protozoa1,7. Legionella are taken up into amoeba without being digested and replicate there within vacuoles. When the Legionella have reached a certain density, the vacuoles release them into the water system8.
Why is Pseudomonas aeruginosa of particular concern?
Pseudomonas aeruginosa is one of the most problematic bacteria in healthcare facilities and it is responsible for about 10-20% of hospital acquired infections (HAIs) in ICUs (pneumonia, wound infections, blood stream infections and urinary tract infections)5. Several studies have shown that up to 42% of the hospital acquired P. aeruginosa infections may be derived from the water distribution system9-11. Infection chains from water taps to patients have been reported. P. aeruginosa easily colonizes all kinds of fluids (even distilled water) and rapidly forms biofilms5. P. aeruginosa strains have developed resistance against commonly used antibiotics, rendering effective treatment increasingly complicated and expensive4,12.
What are the pathways for infection
transmission from water sources to patients?
Inhalation and aspiration represent transmission pathways for Legionella spp. Pseudomonas spp. can be transmitted by contact. During daily routines, water from faucets is used by nursing staff for personal hygiene of patients. Due to the severity of their disease states, ICU patients are often fitted with multiple access devices such as catheters, drains and tracheal tubes. These portals of entry represent potential entrance sites for bacteria. Droplets of contaminated tap water or the contaminated hands of nursing staff can accidentally come into contact with those entrance sites. Rogues et al. recently reported that 14% of ICU health care workers hands were Pseudomonas positive when washed with contaminated tap water and 12% were positive when the last contact was with a Pseudomonas positive patient13. Contaminated bottled water has also been described as a source of hospital-associated Pseudomonas infections in ICUs14.
Why is complete biofilm eradication by systemic treatments so difficult?
Water distribution systems in large buildings are frequently complex networks. Dead ends, corroded pipes, and insufficient temperatures below 55 °C in the warm water pipes contribute to biofilm formation and prevent complete eradication of biofilm. Heat and flush procedures (10-20 minutes of simultaneous flushing of all outlets with water heated to > 70°C) may have only short term effects15. Thermal procedures can result in warming up cold water16 when hot and cold water pipes are located in the same duct. Chemical treatments are bactericidal to free floating bacteria and may reduce biofilm, but complete eradication of biofilm in large buildings is very difficult15,17. Therefore, areas with immunocompromised patients require additional protective measures to minimize transmission of waterborne pathogens to patients.
Where are point-of-use (POU) water filters (tap and shower filters) used?
Point-of-use (POU) water sterile filters are used as an additional preventative measure in those areas where highly immunocompromised patients come into contact with water1,18-21. They can be installed at faucets (tap filters) or connected to shower hoses (shower filters). Most common areas include bone marrow transplant, hematology/oncology, intensive care, transplantation, burn, and neonatology units, endoscopic reprocessing areas, birth tubs, kitchens (for critical patient food preparation), and geriatric/skilled nursing facilities. Based on clinical experiences, POU sterile filtration is also used in other areas with immunocompromised patients such as nursing homes or home settings with chronically immunocompromised patients. POU filters are quickly installed, which makes them a useful instrument in acute outbreak control, e.g., in public buildings, swimming pools, sports centers or hotels during outbreaks of Legionella (eg.Legionella filters for non-medical markets).
What are the requirements for POU sterile filtration?
POU sterile filtration must deliver water filtered through sterilizing grade membrane filtration in accordance with international standards (retention of 107 Brevundimonas diminuta/cm2 filtration media surface)22. Since POU filters are mostly used in a humid environment for routine washing procedures a risk of contamination of the filter housing exists. In order to minimize this risk of retrograde contamination, Pall-AquasafeTM water filters contain a non-leaching, bacteriostatic additive throughout the housing polymer. Hygienic safety of Pall-Aquasafe POU filters has been demonstrated through laboratory validations and multicenter field evaluations, and independent clinical trials. 
Are there additional advantages of Pall-Aquasafe™ sterile water filtration?
In order to make filter exchange record-keeping easier, Pall-Aquasafe filters are equipped with peelable, writable labels for recording filter exchange information. The exchange can also be monitored electronically using a specific software package (Pall-Aquasafe Data) to deliver an audit traceable trail of filter exchange. Easy filter replacement within seconds is guaranteed using quick connectors that are tailored to the filters. Integrated prefiltration helps to maintain high flow rates over the filter lifetime. Pall-Aquasafe filters are compatible with systemic treatments like continuous heating (at 60 °C), heat and flush procedures (at 70 °C) or chlorine dioxide disinfection. Since POU sterile filtered water is also used as drinking water, filters must fulfill drinking water requirements.
Are there recommendations for point-of-use filtration?
Since 2002, a guideline from the French Ministry of Health has advised that healthcare facilities install 0.2 µm micro-filtration at point of use in high risk areas23. Since 2002, the Robert Koch Institute (RKI) has recommended water filtration during the last rinsing step of endoscopic reprocessing protocols24. In the UK, the Yorkshire Cancer Network states that point-of-use filtered water is the most appropriate option for the provision of potable water for immunocompromised cancer patients25. In 2006, the German Ministry of Environment recommended that water taps in high risk areas should be restricted in use or alternatively point-of-use filtration should be installed above a level of 1 CFU Legionella/100 mL26. In the WHO publication "Legionella and the Prevention of Legionellosis" (2007), point-of-use filters are recommended for high risk areas such as transplant units and ICUs when Legionella free water (0 CFU/100 mL) is not achievable27.
Are there studies on infection reduction after POU filter installation?
Numerous reports from clinical authors have demonstrated the high efficiency of Pall AquasafeTM water filters under clinical conditions18-21,28,29. In addition, Vianelli et al. (2006) reported that the use of disposable filters (Pall-Aquasafe) during a Pseudomonas aeruginosa outbreak in a hematology unit resulted in a highly significant reduction of both colonizations and infections18. Van der Mee-Marquet et al. (2005) documented a reduction in pulmonary, bloodstream and urinary P. aeruginosa infections from 8.7/1000 patient days (before filtration) to 3.9/1000 patient days (after filtration)19. The reduction of infections from multisensitive P. aeruginosa isolates (most probably derived directly from the water) was particularly pronounced. Trautmann et al. (2008) reported on endemic P. aeruginosa infections on a surgical ICU21. Various measures, such as selective digestive tract decontamination, regular change of aerators, or use of bottled sterile water for oral hygiene did not result in a significant reduction of Pseudomonas positive patients. In contrast, the comparison between 12 months pre-filter (n = 649 patients) and post-filter (n = 585 patients) periods revealed a significant 56% reduction of infections (p<0.0003) after installation of disposable POU water filters21.
What economic advantages are provided by point-of-use filtration?
Cost comparisons between sterile bottled water, commercially available mineral water, and sterile filtered water used as drinking water for highly immunocompromised patients revealed significant cost advantages of disposable point-of-use filters20. Any waterborne infection results in higher morbidity and mortality and adds costs to healthcare facilities. The value of POU filtration must therefore also be assessed from a preventive perspective. P. aeruginosa, for example, is known to cause hospital acquired infections in intensive care units (ICUs) such as bloodstream infections, urinary tract infections, surgical wound infections, and pneumonia5. Additional costs for bloodstream infections or pneumonia in ICU patients can easily exceed $15,000 USD per patient31-33. Complete installation of POU water filters in one ICU with ten water taps may yield cost savings even if only one single infection could be avoided annually. In a recent clinical study, cost savings after installation of disposable water filters on 7 ICU taps were estimated at 64,000 USD per year based on the reduction of Pseudomonas infections21.
Waterborne Pathogens and Point-of-Use Filtration - Recent Developments
Research continues in an effort to identify waterborne pathogens and the role that they play in healthcare-associated infections.34-49 In addition, experiences documenting the successful implementation of point-of-use filtration continue to be presented to the healthcare community.50-54References:
1) Exner M. et al., “Prevention and control of health care-associated waterborne infections in health care facilities”, AJIC, 33 (5) S26-S40, 2005
2) Lindsay D. & von Holy A., “Bacterial biofilm within the clinical setting: What healthcare professionals should know”, J Hosp Infect, 64:313-325, 2006
3) Kreysig D., “Der Biofilm – Bildung, Eigenschaften und Wirkungen”, published in Bioforum, GIT Verlag, Darmstadt/Germany, 24:40-43, 2001
4) Anaissie EJ., et al., “The hospital water supply as a source of nosocomial infections: a plea for action.” Arch Intern Med, 162:1483-1492, 2002
5) Wunderink RG. & Mendoza DL., “Epidemiology of Pseudomonas aeruginosa in the intensive care unit”, published in “Infectious diseases in critical care”; Springer Verlag, 218-225, 2007
6) Trautmann M. et al., “Common RAPD pattern of Pseudomonas aeruginosa from patients and tap water in medical intensive care unit”, Int J Hyg Environ-Health, 209:325-331, 2006
7) Drancourt M., Adékambi T. & Raoult D., “Interactions between Mycobacterium xenopi, amoeba and human cells”, J Hosp Infect, 65:138-142, 2007
8) Winiecka-Krusnell J. & Linder E., “Free living amoeba protecting Legionella in water: The tip of an iceberg?”, Scand J Infect Dis, 31:383-385, 1999
9) Reuter S. et al., “Analysis of transmission pathways of Pseudomonas aeruginosa between patients and tap water outlets”. Crit Care Med, 10:2222-2228, 2002
10) Blanc DS. et al., “Faucets as a reservoir of endemic Pseudomonas aeruginosa colonization/infections in intensive care units”, Intensive Care Med, 30: 1964-1968, 2004
11) Vallés J. et al, “Patterns of colonization by Pseudomonas aeruginosa in intubated patients: a 3-year prospective study of 1.607 isolates using pulsed-field gel electrophoresis with implications for prevention of ventilator-associated pneumonia”, Intensive Care Med, 30:1768-1775, 2004
12) Jung R. et al., “Surveillance of multi-drug resistant Pseudomonas aeruginosa in an urban tertiary-care teaching hospital”, J Hosp Infect, 57:105-111, 2004
13) Rogues AM. et al., "Contribution of tap water to patient colonisation with Pseudomonas aeruginosa in a medical intensive care unit", J Hosp Infect, 67:72-78, 2007
14) Eckmanns T. et al., "An outbreak of hospital-acquired Pseudomonas aeruginosa infections caused by contaminated bottled water in intensive care units", Clin Microbiol Infect, 14:454-458, 2008
15) Blanc D. et al., “Water disinfection with ozone, copper and silver ions, and temperature increase to control Legionella: seven years of experience in a university teaching hospital”, J Hosp Infect., 60, 2005
16) Patterson et al., “Colonization of transplant unit water supplies with Legionella and protozoa: precautions required to reduce the risk of legionellosis”, J Hosp Infect, 37:7-17, 1997
17) Eckmanns T. et al., “Prevention of nosocomial Legionnaire’s disease”, Dtsch ™rztebl, 103:1294-1300, 2006
18) Vianelli N. et al., “Resolution of a Pseudomonas aeruginosa outbreak in a haematology unit with the use of disposable sterile water filters”, Haematologica, 91:983-985, 2006
19) Van der Mee-Marquet N. et al., “Water Microfiltration: A procedure to prevent Pseudomonas aeruginosa infection”, XVIe Congrès National de la Société Francaise d’Hygiène Hospitalière, Reims, Livre des Résumés, S137, June 4th 2005
20) Hall J. et al.,"Provision of safe potable water for immunocompromised patients in hospital", J Hosp Infect, 58:155-158, 2004
21) Trautmann M. et al., "Point-of-use water filtration reduces endemic Pseudomonas aeruginosa infections on a surgical intensive care unit", Am J Infect Control, 36:421-429, 2008
22) American Standard Test Method (ASTM) F838-05 “Determining Bacterial Retention of Membrane Filters Utilised for Liquid Filtration”
23) Circulaire DGS/SD7A/SD5C-DHOS/E4 n° 2002/243 du 22/04/2002 relative à la prévention du risque ilé aux legionelles dans les établissements de santé, April 22nd,l 2002
24) Empfehlung der Kommission für Krankenhaushygiene und Infektionspr™vention beim Robert Koch-Institut (RKI), “Anforderung an die Hygiene bei der Aufbereitung flexibler Endoskope und endoskopischen Zusatzinstrumentariums“, Bundesgesundheitsbl-Gesundheitsforsch-Gesundheitsschutz, 45:395-411, 2002
25) Yorkshire Cancer Network, “Provision of safe drinking water for cancer patients with immunocompromised”, http://www.yorkshire-cancer-net.org.uk/, 2005
26) “Empfehlung des Umweltbundesamts nach Anhörung der Trinkwasserkommission des Bundesministeriums für Gesundheit“, Bundesgesundheitsbl-Gesundheitsforsch-Gesundheitsschutz, 49:697-700, 2006
27) "Legionella and the prevention of Legionellosis", WHO Press, World Health Organization, Geneva/Switzerland, Editors: J. Bartram, Y. Chartier, JV Lee, K. Pond & S. Surman-Lee, 2007
28) Sheffer PJ. et al., “Efficacy of new point-of-use water filter for preventing exposure to Legionella and waterborne bacteria”, AJIC, 33 (5) S20-S25, 2005
29) Harpel S. et al., “Performance of a new 14 day water filter during daily use in clinical routine at two university medical centers”, J Hosp Infect, 64 (Suppl.1):S47, 2006
30) "Legionella and the prevention of Legionellosis", WHO Press, World Health Organization, Geneva/Switzerland, Editors: J. Bartram, Y. Chartier, JV Lee, K. Pond & S. Surman-Lee, 2007
31) Pirson et al., “Cost associated with hospital-acquired bacteraemia in a Belgian hospital”, J Hosp Infect, 59:33-40, 2005
32) Murphy D., Whiting J. & Hollenbeak CS., “Dispelling the myths: The true cost of health care associated infections”, APIC Briefing, Feb. 2007, http://www.apic.org/
33) Warren KD. et al., “Attributable cost of catheter-associated bloodstream infections among intensive care patients in a nonteaching hospital”, Crit Care Med, 34:2084-2089, 2006
34) Angelbeck, J. Ortolano, G. Canonica, F. Cervia, J. “Hospital Water: A Source of Concern for Infections.” Managing Infection Control. 2006. 6(1): 44-54
35) Cervia, J. Canonica, F. Ortolano, G. “Danger on Tap: Water as a Source of Healthcare-Associated Infection.” Life Sciences BTR. Winter 2006(6):86-87
36) Ortolano, G. Cervia, J. Canonica, F. McAlister, M. “A Waterborne Hospital Pathogen’s ‘Fantastic Voyage.’” Managing Infection Control. 2006. 6(11):102-106.
37) Cervia, J. Canonica, F. Ortolano, G. “Water as a Source of Health Care-Associated Infections.” Archives of Internal Medicine. 2007. 167:92.
38) Ortolano, G. Canonica, F. Cervia, J. “Waterborne Pathogens in Health Care: Critical to Quality.” Infection Control Today. 2007.11(4):36-38.
39) Ortolano, G. Canonica, F. Cervia, J. “Point-of-Use Water Filtration Complements Systemic Treatment to Reduce Health Care-Associated Legionnaires Disease.” Clinical Infectious Diseases. 2007.45(1):135-136.
40) Cervia, J. Ortolano, J. Canonica, F. “Hospital Tap Water as a Source of Stenotrophomonas maltophilia Infection.” Clinical Infectious Diseases. 2008.46(9):1485-1487
41) Cervia, J. Maguire, J. “Veterans Health Administration Issues New Legionella Directive.” American Association for Respiratory Care's Management Specialty Section Bulletin. 2008. Spring e-Newsletter:3.
42) Maguire, J. Cervia, J. “Payment System Brings Focus to Waterborne Health Care-Associated Infection.” Chest Physician. 2008.3(4):16.
43) Cervia, J. Canonica, F. Ortolano, G. Maguire, J. “Waterborne Pathogens Pose Preventable Risks to Ventilated and Critically Ill Patients.” RT for Decision Makers in Respiratory Care. 2008.21(10):38-39. Also e-published at http://www.rtmagazine.com/issues/articles/2008-10_10.asp?mode=print .
44) Cervia, J. Ortolano, G. Canonica, F. “Hospital Tap Water: A Reservoir of Risk for Healthcare-Associated Infection.” Infectious Diseases in Clinical Practice. 2008. 16(6):349-353. e-Published Ahead of Print, October 21, 2008. 10.1097/IPC.0b013e318181fa5e.
45) Cervia, J. Farber, B. Armellino, D. Canonica, F. Ortolano, G. “Hospital Water: A Possible Source of Healthcare-Associated Infections in Bone Marrow Transplant Recipients.” American Federation for Medical Research 2008 Eastern Regional Meeting. (Abstract). Oral Symposium Presentation. April 9, 2008. Washington, D.C. Abstract #473893. Publication In: Journal of Investigative Medicine. 2008. 56(5):808. Abstract #7.
46) Hirsch, B. Canonica, F. Cervia, J. Armellino, D. Schilling, M. “An Unsuspected Locus of Waterborne Pathogens (WBP) in the ICU.” Abstracts of the 48th Interscience Conference on Antimicrobial Agents and Chemotherapy/46th Infectious Diseases Society of America Annual Meeting (Abstract). October 2008:575 (#K-4118). 48th Interscience Conference on Antimicrobial Agents and Chemotherapy/46th Infectious Diseases Society of America Annual Meeting. Poster Presentation. October 28, 2008. Washington, D.C. Abstract #2707.
47) Cervia, J. Ortolano, G. Canonica, F. “A Waterborne Hospital Pathogen’s ‘Fantastic Voyage’—The Sequel.” Managing Infection Control. 2009. 9(4):22-32.
48) Cervia, J. Ortolano, G. Canonica, F. “Stemming the Tide of Waterborne Healthcare-Associated Infection Risk.” Association for Healthcare Risk Management of New York News. 2009.Winter:6-11.
49) Cervia, J. Ortolano, G. Canonica, F. McAlister, M. "Role of Biofilm in Pseudomonas aeruginosa Colonization and Infection." Infection Control and Hospital Epidemiology. 2009. 30(9):925-927.
50) Ortolano, G. Canonica, F. McAlister M. Cervia, J. “Hospital Water as a Reservoir of Risk for Healthcare-Associated Infection.” Water Microbiology: Types, Analyses, and Disease-Causing Microorganisms. Nova Science Publishers. 2009. (In Press).
51) Holmes, C. Cervia, J. Ortolano, G. Canonica, F. “Preventive Efficacy and Cost-Effectiveness of Point-of-Use Water Filtration in a Sub-acute Care Unit.” National Association of Long Term Hospitals 2009 Physician Education Conference: Long-Term Acute Care: Management of Prolonged Severe Illness. (Abstract). Poster Presentation. October 21-23, 2009. Omni Mandalay Hotel at Las Colinas, Dallas, TX
52) Cervia, J. Farber, B. Armellino, D. Klocke, J. Bayer, R. McAlister, M. Stanchfield, I. Canonica, F. Ortolano, G. “Point-of-Use Water Filtration Reduces Healthcare-Associated Infections in Bone Marrow Transplant Recipients.” 137th American Public Health Association Annual Meeting. Oral Presentation. November 9, 2009. Philadelphia, PA. Abstract #192866.
53) Holmes, C. Cervia, J. Ortolano, G. Canonica, F. “Preventive Efficacy and Cost-Effectiveness of Point-of-Use Water Filtration in a Sub-acute Care Unit.” American Journal of Infection Control. (In Press).
54) Cervia, J. Farber, B. Armellino, D. Klocke, J. Bayer, R. McAlister, M. Stanchfield, I. Canonica, F. Ortolano, G. “Point-of-Use Water Filtration Reduces Healthcare-Associated Infections in Bone Marrow Transplant Recipients.” Transplant Infectious Disease. (In Press).
