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Keeping Afloat in a Rising Tide of Waterborne HAIs: 8 Facts Healthcare Leaders Must Know

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6. WBPs may be intractably resistant to control.
Ubiquitous in hospital plumbing as in nature, biofilm may be recognized as the slippery material coating wet surfaces, like the slimy material on stones that one may feel between one’s toes when wading barefoot in a body of water.  Scientists define biofilm as a microbially-derived sessile community characterized by cells that are irreversibly attached to a substratum or to one another, are embedded in a matrix of extracellular polymeric substances that they have produced, and exhibit altered characteristics with respect to growth rate and gene transcription.(25) Biofilm affords microbial pathogens protection from adverse environmental conditions outside the host;(26)  and, it has been established that biofilm bacteria display a higher level of resistance to antimicrobial agents(27-31) and environmental controls (e.g. ultraviolet light, metals, and acid pH) (32-34) than do planktonic (free-floating) bacteria. Interestingly, for clinically important organisms such as P. aeruginosa, a single genetic locus has been identified to be associated with both the ability to form biofilm and antimicrobial resistance.(35)

The ability to form and maintain biofilm communities for protection from adverse environmental conditions has permitted WBP to survive, thrive, and to evolve further mechanisms for resistance to outside threats across millennia. Thus, our difficulties in detecting and eradicating these organisms by means of altering environmental conditions in our water distribution systems should come as no surprise. 

7. Reducing WBP risk to patients and healthcare institutions requires a proactive and multi-dimensional approach.
Methods used to protect patients and water systems must adequately address biofilm in order to be effective. A number of preventive strategies have been employed by healthcare facilities, usually in response to an outbreak. They include: hot water flushing of the plumbing system, chlorination, chlorine dioxide, monochloramine (used exclusively at the municipal treatment level in the U.S.), copper-silver ionization, ultraviolet light (UV), ozonation, and POU water filtration. Each method has advantages and disadvantages related to ease of implementation, cost, maintenance issues, and short- and long-term effectiveness. Aside from POU filtration, these methods are often incompletely effective in the long-term. Maintenance of systemic disinfection agents at levels that consistently prevent recolonization and biofilm elaboration despite variability in water quality due to seasonal changes and facility construction is difficult. Once reestablished, biofilm effectively protects microbes against the harsh effects of systemic disinfection strategies.

Of these preventive methods, flushing all parts of the plumbing system at temperatures of greater than 65 degrees C is perhaps the easiest to implement, but precludes the use of water outlets during the procedure, occupies substantial facility management staff resources, and presents a risk of scalding. Recent data corroborate earlier observations that hot water flushing is inadequate in eliminating Legionella from plumbing systems over the longer term,(36) even though temperatures above 59 degrees C were associated with an inability to culture Legionella.(37-38)  One study disclosed that a system flush using hot water at 80 degrees C was incapable of eradicating Legionella serogroup 5.39  In fact, one published observation documented the presence of a persistent strain of Legionella in a hospital over the course of 15 years.(40) 

Chlorination is also relatively simple to establish; however, it can be challenging to maintain adequate levels of chlorine throughout a hospital water system.  Electrolytic chlorine generation systems in large-scale studies appear to be no better than sodium hypochlorite.(41) However, chlorination is not free of risk for possible byproduct-associated genotoxicity, which is an emerging concern.(42) Bench-scale chlorination compared with UV irradiation showed that both methods were effective in reducing levels of indicator organisms; however, pathogens of clinical concern were less affected by chlorination.(43) Published data demonstrate that waterborne pathogens are protected against chlorination by biofilm.(44-45)  These findings suggest that chlorination may be less effective than other alternatives, despite its relative cost efficiencies.

Chlorine dioxide effectively reduces, but may not eliminate Legionella.(46) Testing of multiple disinfection strategies has indicated that chlorine dioxide may arguably be the most effective systemic disinfection method for the control of Legionella.(44) In simulated potable water system testing, chlorine dioxide was shown to be more effective in reducing heterotrophic bacterial counts, with reduced levels of some but not all organic halogenated byproducts.(47) However, chlorine dioxide systems are more costly to install than chlorination.

Efficacy studies of chloramines alone or in combination with free chlorine indicate that neither alone is adequate as a disinfectant.(48) In addition, the spectrum of potentially harmful halogenated byproducts left by combination chlorination regimens(49) will take some time to assess.  Chlorine and chloramines also differ in their spectrum of antimicrobial activity. For example, Klebsiella pneumoniae appears to be more sensitive to chloramines than to free chlorine under certain conditions.(50)

Studies of copper-silver ionization used either alone or in combination with other systemic disinfection strategies have demonstrated this technology to be effective to varying degrees.(51) However, it is likely to be more effective when used in combination with another disinfection technology.  Importantly, none of these studies was able to demonstrate sustained eradication of Legionella; however, acutely, copper and silver ions alone and in combination have demonstrated bactericidal activity of greater than 99.999 percent against the clinically relevant WBP, such as P. aeruginosa, A. baumannii, and S. maltophilia, in addition to Legionella.(52-53)

UV irradiation, which is rarely used in the hospital setting in the U.S., has poor penetrating power, is only effective at the source of irradiation, and remains prone to fouling of the quartz sleeves surrounding the UV lamp.(54)  One notable advance is the use of light emitting diodes to deliver UVA radiation, which has been shown to be effective as a bactericidal treatment. However, this technology awaits further characterization.(55)  Like other combinations of systemic disinfection strategies, it should not be surprising that UV and ozonation used in combination have been shown to be better than either used alone.(56)  

POU water filtration offers the potential benefit of immediate and complete effectiveness against waterborne bacteria, fungi, and protozoa.  Although the implementation of POU water filtration for at-risk patient populations in the healthcare setting is a relatively new phenomenon in the U.S., this technology has been used extensively in Europe for over a decade. POU filtration studies have appeared extensively in the scientific literature and have repeatedly addressed the role of filtration technology in both reducing infections due to WBP and reducing costs for healthcare institutions.(14)
Laboratory and clinical studies have validated the efficacy of POU filters in removing WBP.  In one such validation study, two counter-top goose neck faucets were attached to a laboratory model plumbing system. A 0.005 µm point-of-use filter (Nephros Inc., River Edge, New Jersey) was attached to a test faucet. Environmental isolates of Legionella, Pseudomonas, Stenotrophomonas, Acinetobacter, Klebsiella, and Mycobacterium were added to the model plumbing system to reach the starting bacterial concentration for each organism at above 3x103 cfu/mL. Water and swab samples were withdrawn at T = 1, 2, 3, 4, 5, 7 and 14 days from both the test faucet (after filtration) and control faucet (no filtration). A standardized microbiological method was followed for cultures of each organism.  During the 14-day study, more than 30,000 liters of water was run through the filter. Results showed that the point-of-use filter successfully removed L. pneumophila, P. aeruginosa, S. maltophilia, A. baumannii, K. pneumoniae, and M. abcessens from the model plumbing system. No test pathogens were cultured in both water and swab samples from the test faucet. Approximately 2,500,000 cfu/mL of test pathogens, on average, were recovered from the control faucet.(57)  Sheffer, et al.(58)  conducted a study during which it was demonstrated that POU filters labeled for a maximum use life of seven days completely eliminated L. pneumophila and Mycobacterium gordonae from hot tap water over an eight-day period of use. Vonberg, et al.(59)  observed that 99.6 percent of 256 filtered water samples obtained during their study were devoid of Legionella spp. 

After an observation period of 11 months, during which a high incidence of P. aeruginosa bacteremia was observed in a hematology unit with severely neutropenic patients, Vianelli, et al.(60)  performed extensive sampling in an attempt to trace the environmental source of the isolates that were appearing in patient blood cultures. Upon identifying faucets and showers in the unit as the primary environmental sources of those isolates, POU filters were installed on all hematology unit water outlets. Highly statistically significant reductions in bloodstream infections were subsequently observed over the course of the next two years.

In a study spanning a period of two years, Trautmann, et al.(61)  documented a decrease in the monthly rate of P. aeruginosa infections in a surgical intensive care unit (SICU) from 2.5 per month prior to POU filter installation to 0.8 per month after POU filter installation. Van der Mee-Marquet, et al.(62) surveyed pseudomonal infections of blood, urological, and pulmonary origin over 23,611 patient days in an intensive care unit over a period of 7.5 years. During a timeframe of 2.5 years prior to the use of POU filtration, 8.7 infections per 1,000 patient days were observed, while in the five years after installation of POU filters, only 3.2 infections per 1,000 patient days were recorded. 

In a neonatal intensive care unit, La Ferriere(63) employed a variety of infection control interventions, including POU filtration, in order to effect a dramatic decline in HAIs attributable to P. aeruginosa.  More recent clinical studies have demonstrated the efficacy and cost-effectiveness of POU filtration in reducing the risk of infections for bone marrow transplant recipients,(64) and patients in sub-acute care.(65)

Though extremely reliable, potential limitations of a POU water filtration strategy include the risk of possible retrograde contamination of incoming tap water,(66) limited filter use life, and the additional cost of POU filters. With respect to these concerns, it is important to note that not all POU filters are alike. Filters designed for under sink installation are less subject to retrograde splash or touch contamination. In addition, some POU filters are considerably less vulnerable to fouling, and thus labeled for more extended use lives.  Such practical advantages may add considerably to the efficiency and cost-effectiveness of POU filtration for healthcare facilities.

8. Prevention of HAIs related to WBPs is exceedingly cost-effective.
The added cost incurred for HAIs in U.S. hospitals has been conservatively estimated at $15,275 to $38,656 per infection.(67-68) More recent data from the Agency for Healthcare Research and Quality place additional costs for a single HAI closer to $43,000.(69) While scientific studies have supported the use of POU water filters to reduce at-risk patient exposure to WBP, healthcare institutions that adopt this technology can also realize economic benefits. Hall, et al.(70) demonstrated that costs associated with filtered drinking water supplied to immunocompromised patients were drastically lower than those for both bottled sterile water and commercially available bottled water.  In addition, Trautmann, et al.(71) recounted savings realized on the cost of antibiotics used to treat P. aeruginosa infections in a SICU during implementation of POU water filters on faucets.  Finally, it should be noted that these estimates do not take into account the institutional costs inherent in responding to a recognized outbreak of HAIs or of any resulting litigation.

Going with the Flow or Stemming the Tide?
Despite often highly publicized evidence of risk posed by WBP such as Legionella, and the well-documented efficacy of measures to reduce this risk, the control of WBP in U.S. healthcare institutions remains a work in progress. As has been previously stated, the U.S. lags far behind Europe in recognition of tap water as an important source of HAIs. Currently, the approaches taken by many U.S. healthcare institutions to control WBP vary greatly. 

Vigilance with respect to water quality in U.S. hospitals is not uniform.(72) Some facilities respond to an outbreak by culturing water, and temporarily installing some preventive measure such as POU filters. When the outbreak is interrupted, POU filters are removed, leaving the facility unprotected against the inevitable next outbreak.  Still other institutions adopt an undisciplined and haphazard approach to water culturing, installation of a systemic disinfection technology, and fail to implement complementary POU filtration. This approach leaves the facility continually vulnerable to biofilm in the plumbing system, changes in water pressure, and seasonal variations in water quality. It also ignores recent studies indicating that electronic (non-touch) faucets can harbor and promote the proliferation of WBP due to the fact that their electrical solenoid valves remain warm at all times, providing an incubated environment for planktonic and biofilm-based bacteria, fungi, and protozoa.(73-75) More recently, thought-leading facilities have recognized the importance and cost-effectiveness of performing routine microbial analyses of tap water in at-risk patient areas, installing an appropriate systemic disinfection technology, and pro-actively utilizing POU filtration to protect their most vulnerable patients.

Finding a Safe Harbor
It has been suggested that hospital water distribution systems are among “the most overlooked, important, and controllable sources of HAI.”(8) Available evidence in the peer-reviewed literature has demonstrated that hospital tap water contains microbial pathogens, and that biofilms in water delivery systems resist disinfection and deliver pathogenic organisms into the healthcare environment. At-risk patients are susceptible to infection through direct contact, ingestion, and inhalation of WBP. Systemic water treatment technologies reduce levels of recognized WBP; however, they vary in initial and long-term maintenance costs, efficacy against specific organisms, and compatibility with facility plumbing system materials. Moreover, they do not permanently and completely eradicate biofilms within healthcare facility plumbing. Finally, existing POU filtration technologies have been reported to interrupt clinical outbreaks of infection due to recognized WBP in the healthcare environment, and can represent a critical component of a comprehensive infection control strategy, particularly when pro-actively targeted for patients at high risk.

Joseph S. Cervia, MD, MBA, FACP, FAAP, FIDSA, is clinical professor of medicine and pediatrics at Albert Einstein College of Medicine and Hofstra-North Shore LIJ School of Medicine.

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