Peer-Reviewed Research Study

Experiences of the First 16 Hospitals Using Copper-Silver Ionization for Legionella Control: Implications for the Evaluation of Other Disinfection Modalities

JANET E. STOUT, VICTOR L. YU
CAMBRIDGE UNIVERSITY PRESS, INFECTION CONTROL AND HOSPITAL EPIDEMIOLOGY, AUGUST 2003

Introduction
This study examined 16 acute care hospitals using copper-silver ionization as a disinfection method. Surveys were deployed in 1995 and 2000 to gather information from each hospital. The 2000 survey was up to 11 years after installation for some hospitals.

Results
Before installing a copper-silver ionization system, all 16 hospitals had reported cases of hospital-acquired Legionnaires’ disease. Seventy-five percent had tried other disinfection methods, including superheat-and-flush, ultraviolet light, and hyperchlorination.

After installing a copper-silver ionization system, no cases of hospital-acquired Legionnaires’ disease were reported, and the Legionella positivity rate (percentage of test sites within the hospital positive for Legionella) was significantly reduced.

Before installation: 47% of the hospitals reported a Legionella positivity rate of 30% or higher
1995 (zero to six years after installation): 50% of the hospitals reported a Legionella positivity rate of 0%
2000 (five to 11 years after installation): 43% of the hospitals reported a Legionella positivity rate of 0%

The study found that the infection control practitioners rated the disinfection system as “excellent.” The engineers rated the operation and maintenance of the system as “average” (not easy, but also not difficult).

Conclusion
The team behind this study developed a standardized, evidence-based approach to assist hospitals with evaluating different disinfection methods. The four criteria a disinfection method must meet include the following:

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.

At the time of this study, copper-silver ionization was the only disinfection modality to have fulfilled all four evaluation criteria.

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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.