Yusen Lin, Janet E. Stout, Victor Yu
Cambridge University Press, Infection Control and Hospital Epidemiology, February 2011
Introduction
This study reviewed the efficacy of different disinfection methods for controlling Legionella in hospitals, including copper-silver ionization, chlorine dioxide, hyperchlorination, monochloramine, UV, point-of-use filtration, and superheat-and-flush.
The four criteria each disinfection method must meet to validate efficacy include:
- Proof it kills Legionella in a lab study.
- Anecdotal reports of it controlling Legionella in individual hospitals.
- Peer-reviewed reports of it controlling Legionella in individual hospitals over a prolonged period.
- Confirmatory reports of it controlling Legionella in multiple hospitals over a prolonged period.
Results
A summary of findings for each disinfection method is included below.
Copper-silver ionization
– Only method validated by the four criteria
– Easy installation and maintenance
– Not impacted by higher temperatures
– Residual levels are maintained for a prolonged period
– Efficacy declines in pH greater than 8.5
Chlorine dioxide
– Penetrates biofilm
– Effective over a wide range of pH levels
– Creates harmful byproducts
– Difficult to maintain residual levels
Monochloramine
– Penetrates biofilm
– Effective over a wide range of pH levels
– Can cause anemia in dialysis patients
– On-site generation can be complicated
Hyperchlorination
– Most expensive and unreliable of all methods
– Causes corrosion
– Does not penetrate biofilm
– Introduces carcinogens into the water
Point-of-use filtration
– Effective against Legionella and Mycobacterium
– Provides immediate protection making them a good option for outbreaks
– Not cost-effective for long-term use
UV
– Non-chemical
– Works best when installed on the incoming water supply
– Does not provide systemic disinfection
Superheat-and-flush
– Effective in emergencies
– Not effective for prolonged use
– Limited to hot water lines
Conclusion
There are several viable methods for controlling Legionella, but copper-silver ionization was the only method validated by the four criteria at the time of this study. The researchers concluded that “copper-silver ionization appears to be the best available technology today for controlling Legionella colonization in hospital water systems.” They suggested that rigorous maintenance plans, regular monitoring of ion concentrations, and frequent Legionella testing are necessary to ensure long-term success.
