Peer-Reviewed Research Study

Controlled Evaluation of Copper-Silver Ionization in Eradicating Legionella pneumophila from a Hospital Water Distribution System

Zeming Liu, Janet E. Stout, Lou Tedesco, Marcia Bolding, Charles Hwang, Warren F. Diven, Victor L. Yu
The University of Chicago Press, The Journal of Infectious Diseases, April 1994

Introduction
This study evaluated the efficacy of copper-silver ionization in a hospital with active Legionella colonization after superheat-and-flush and hyperchlorination had proven ineffective.

Results
Six months after installation, the Legionella positivity rate (percentage of test sites within the building positive for Legionella) dropped significantly in the test building.

Test building: Legionella positivity rate reduced from 50% to 0.8% after six months
Control building (no copper-silver ionization): Mean positivity rate of 67% for study duration

The copper-silver ionization systems were turned off to assess the length of time before Legionella recolonization. The test building remained negative for two months, with only one of the 26 test sites showing Legionella after four months. The control building remained positive.

Conclusion
Copper-silver ionization successfully eliminated Legionella in the hospital’s water system. The advantages of copper-silver ionization include relatively low cost, straightforward installation, easy maintenance, nontoxic by-products, and the presence of a disinfecting residual.

Full study

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Highlighted author

Dr. Janet E. Stout

Dr. Janet E. Stout is the president and director of the Special Pathogens Laboratory, and a research associate professor at the University of Pittsburgh. A clinical and environmental microbiologist, Dr. Stout is internationally recognized for more than 30 years of research in Legionella and is credited as the first to demonstrate the link between Legionnaires' disease and the presence of Legionella in hospital water systems. Dr. Stout was instrumental in developing the first US prevention strategy for hospital-acquired Legionnaires' disease that now serves as the model for national Legionella guidelines. She serves on the Legionella standards committees for the America Society of Heating, Refrigerating and Air-Conditioning Engineers' (ASHRAE) Standards 12 and the proposed Legionella standard.