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Preventing Legionnaires’ Disease in Healthcare Facilities Part 2: How Our Legionella Experiences Shaped our Prevention Approaches

Posted on by CDC's Safe Healthcare Blog
Legionella pneumophila
Legionella pneumophila

Guest Author: John Letson, Vice President Plant Operations, Memorial Sloan Kettering Cancer Center

Memorial Sloan Kettering Cancer Center (MSK) has a 470 inpatient bed hospital, outpatient clinics, and research facility headquartered on the upper east side of Manhattan, with additional outpatient treatment centers in Brooklyn; Long Island; Westchester County, New York; and New Jersey. The well-being of our patients is the primary concern of all doctors, nurses, and staff. The at-risk patients at MSK basically are in two groups. First, cancer patients receiving chemotherapy, including those with combinations of factors placing them at greatest risk, e.g. a patient who smokes and has respiratory issues in addition to having a cancer for which they are receiving chemotherapy. Second, bone marrow transplant patients. The majority of patients diagnosed at MSK with community acquired Legionella in the past have been bone marrow transplant patients. As cancer care continues to move to more outpatient treatment plans, all building owners need to be cognizant of the dangers Legionella poses. It is important to be proactive in preventing the bacteria from propagating in building water systems to preserve the health and safety of everyone.

For more information about MSK and background on our successful Legionella water management program, read my blog entry.

EXPERIENCE CHANGES THE APPROACH

One of the most feared environmental scenarios in healthcare, would be to have a Legionella outbreak. In addition it can be quite alarming when one encounters an “outbreak” of consistently positive environmental cultures. MSK has not experienced any Legionella “outbreaks” where tests show consistent levels of positive colony forming units at many multiple distal sites and buildings. But, MSK has had instances when we had a number of positive Legionella test culture results near locations where patients tested positive for Legionella. The resultant circumstances are the same whether wide spread in a general population or isolated in an at-risk population. The resources required during any outbreak scenario will vary. So here is a brief history of MSK’s experience with positive culture results and the ensuing changes that occurred in mitigation response activities, long term mitigation activities, and the evolution of testing and monitoring.

In 1999 MSK experienced a Legionella positive patient at the same interval as a positive environmental shower culture result and a timeline that suggested it was hospital-acquired. The patient was a bone marrow transplant patient and the Legionella types from the patient and shower were the same. At the time it could not be proven that the patient’s disease was hospital-acquired. Following this event, in 2000, MSK selected and implemented copper-silver ionization as a long term mitigation methodology on the potable hot water system in all in-patient areas. We also adopted a zero tolerance for any Legionella in any water system. As a result of this long term mitigation strategy, positive cultures were eliminated for the next seven years until November 2007, when multiple environmental test culture results came back grossly contaminated for Legionella. This was strange because we went from no positive cultures to such a high level in a short period, so we sent samples to the same lab for retest; as well as to a second, different lab. The same lab (as the previous samples were sent to) report came back contaminated again, but the new lab report came back all negative. We performed mitigation anyway, retested (results negative again), and returned to service. MSK changed labs following this event. This experience validated the importance of using a lab knowledgeable in testing protocols for Legionella or one listed as being CDC ELITE certified.

MSK experienced another positive culture on September 2, 2010. We performed mitigation in this case sanitizing the affected potable water tanks, and retested which came back negative, and were returned to service. While we did not make the correlation at the time, this positive culture was attributable to heavy rain activity during the end of August 2010.

Another positive culture occurred almost one year later. There was one positive culture on September 7, 2011, and one positive case at the same time; both Legionella pneumophila serogroup one. We performed mitigation, retested which came back negative, and returned to service. On subsequent NYC Department of Health Pulsed Field Gel Electrophoresis (PFGE) the testing showed the serogroup in the environmental culture and patient culture were different, so the case was concluded as community-acquired. Similar to the previous event we noted increases in positive cultures in potable water tanks following heavy rain. This was observed at times following heavy thunderstorms or in this instance hurricane activity. This was thought due to the increased runoff and turbulence into open water reservoirs and settling ponds. The runoff which may have washed and disturbed bacteria and organic material from soil and Legionella from biofilms into the source water. Increased organics and pathogen content overwhelms oxidizing biocides and other water purification methods, permitting some bacteria to survive and enter the water system. The positive environmental cultures of September 7, 2011 were directly attributable to hurricane Irene which hit the New York area in late August. As a result, we now test potable water storage tanks a week to ten days after heavy rain events over two inches in order to provide proactive mitigation if required.

There are additional affects an institution could experience based on positive patient cases of Legionella; even if the case is community-acquired. So how does an event change views and practices around potable water safety? Patients and staff have a lack of confidence in the potable water source and utility. Mitigation and extended monitoring is required to reinforce that water is safe when others feel it may not be. Everyone feels at risk—not just the patient. Our experience is staff become highly sensitive and concerned about the level of risk from the water supply.

LONG TERM REMEDIATION

As stated earlier, in 2000 MSK adopted and maintained a zero tolerance policy for Legionella. We adopted the policy in conjunction with implementation of copper-silver ionization on the potable hot water in all in-patient areas. Any positive culture at minimum requires a retest and in some cases enhanced mitigations of hyper-chlorination and flushing, increased ionizer levels, and a second retest to confirm effectiveness. We accomplish and maintain this policy by continually performing:

  • Risk analysis is done in conjunction with the infectious disease department to identify potential sources of bacteria and outline monitoring and mitigation responses.
  • Regular mitigation and maintenance including potable tank cleaning, riser flushing, cooling tower cleaning and chemical water treatment. In the case of cooling tower water treatment, we maintain the zero tolerance due to our patient population instead of under the 1000CFU/liter OSHA standard.
  • Copper-silver units require regular cleaning, monitoring (testing), maintenance, and occasional repairs to be continually effective. We rebar our units every 18 to 24 months. The copper-silver units in our view are the closest thing to plug and play you can get.
  • Regular testing is key to the success or failure of any water treatment program. It qualifies the effectiveness of any mitigation and enables a proactive response to a positive culture.
  • Monitor and qualify new construction; new construction areas are a potential source of Legionella due to water being shut off for extended periods creating dead legs and any dirt or debris that may be left in the piping during construction activities. MSK’s process is to flush, sanitize, and test prior to placing new piping in service.

TESTING, TESTING, TESTING 

Testing is key to success. We have always advocated testing of water systems including potable water tanks, random potable water distal sites, specifically hot water in showers, and cooling towers. Some states mandate testing dependent on patient population. State of NY requires quarterly water system testing where immune-compromised and transplant patient populations undergo treatment. In our experience in the past 16 years, testing has served to exonerate MSK when serogroup between patient case and cultured distal sites did not match. 

Let your testing evolve to suit your conditions. MSK’s testing began and evolved as follows:

  • Potable water tanks were originally tested annually, which evolved to quarterly to be consistent with all other testing. Following two sequential years of a positive culture in 2010 and 2011, we now do weekly testing for a month following a rain event in excess of 2 inches or a hurricane as it was determined that there were elevated counts following major runoffs.
  • Random potable hot water at shower distal sites began and remains at quarterly intervals. Copper-silver ionization systems continue to provide outstanding results since installed in 2000. At that time, distal site random cultures previously consistently positive became negative in just two weeks and have remained that way since. We take both a bulk water sample and a swab at each site and send out 20 sites per quarter.
  • We do additional potable water samples for copper and silver levels once a month to ensure the levels are maintained within range.
  • Cooling towers began quarterly; we changed to monthly from June to September as we kept getting positive cultures in the 3rd quarter. Monthly testing during the cooling season allows mitigation to be more real-time and has eliminated most September positives.
  • All testing is completed at a 3rd party lab. We use one of the most well recognized labs on the east coast.

ASHRAE 188 defines a systematic approach similar to what has been done effectively at MSK for the past 16 years.

The CDC’s toolkit, Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings, reinforces and breaks down ASHRAE 188 into practical action based guide to help building and healthcare providers develop new policies and methodologies to proactively prevent this disease. Having gone through these steps years before, due to our patient population, MSK does not view the standard as added work or responsibility, only a reaffirmation that what we have done here for years is the right thing to do.

Posted on by CDC's Safe Healthcare Blog

2 comments on “Preventing Legionnaires’ Disease in Healthcare Facilities Part 2: How Our Legionella Experiences Shaped our Prevention Approaches”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    Thanks for sharing this success story, John. I hope it will inspire other hospitals to implement and validate water management plans.

    Thanks for the information on legionnaires’ disease. There are many healthcare programs to prevent such diseases with better facilities.

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