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Water Sampling for Legionella: Managing Positive Results
Stem cell transplant patients pose major challenges for preventing infections and infection associated mortality. The CDC and FACT-JACIE recommend periodic sampling of water supply sources for microbial contamination, including Legionella, as an infection prevention strategy.
Sarah Cannon at Tristar Centennial Medical Center is housed in a building constructed in the 1960s Water comes from the city of Nashville via a complex plumbing system of storage towers and risers. 2006, the BMT program began sampling for microbial contamination. 2007, samples tested positive for Legionellawith no actual patient infections. January 2008, a secondary Chlorine Dioxide (ClO2) disinfection system was installed to chemically treat the water. The system analyzes biocide levels and transmits readings to a central station. Concentrations of ClO2 are adjusted to keep biocide levels within specified limits. May 2008 to September 2012, all samples were negative.
Problem
December 2012, one sample tested positive, <1 CFU/mL for Legionella, not the pneumophiliaspecies most linked to illness. April 2013, two samples test trace positive from the Hematologic Malignancy unit connected to the BMT unit. Of note, construction was ongoing within a block with several disruptions to the lines feeding water storage towers. Department leaders hired after installation of the disinfection system had limited knowledge of managing positive samples. Communication of the results, implementing interventions and follow-up was disjointed. A written action plan was not available, necessitating multiple emails, phone calls and meetings.
Intervention
December 2012, the affected room was taken out of service. A work team met to review options with members from infectious disease, administration, nursing, infection prevention, quality/risk management, facility engineering, and the water disinfection system vendor. A thermal eradication and hyperchlorination of the system was ordered and done on the plumbing system.
January and April 2013, frequency of system testing for biocide levels was increased from once a week to twice then three times a week. ClO2 stock solution concentrations were increased to .30 -.40ppm with a target stock tank solution concentration of 250ppm. A schedule for flushing less trafficked areas was implemented to eliminate dead zones. A second thermal eradication was done. Intervention and follow-up times ranged from one week to one month, negatively impacting availability of rooms and sinks. An action plan was created to optimize response including algorithms for BMT/Heme and non-BMT/Heme patients.
Results
June 2013, action plan was complete. July results were reviewed and communicated as directed by the plan. All were negative. Action plan was presented, approved and adopted as a standard procedure by both the BMT and hospital Infection Prevention Committees in August 2013.