Controlling Legionella in hospital water systems: experience with the superheat-and-flush method and copper-silver ionization.
OBJECTIVE
To evaluate the effect of copper-silver ionization on Legionella colonization and nosocomial legionnaires' disease and to compare the efficacy of metal ions versus the superheat-and-flush method of disinfection.


METHODS
Prospective determination over a 36-month period of copper and silver ion concentrations in the recirculating hot-water system, Legionella colonization of the hospital water distribution system, and cases of nosocomial legionnaires' disease. Retrospective comparison of results with the previous 13 years, during which the superheat-and-flush method was used.


METHODS
The Pittsburgh Veterans' Affairs Health Care System (University Drive Division) acute-care hospital.


METHODS
Three copper-silver ionization systems were installed on the hot-water distribution system in November 1994.


RESULTS
The average number of cases of legionnaires' disease per year and the percentage of distal sites positive for Legionella pneumophila for the superheat-and-flush method versus the copper-silver ionization method was six cases with 15% positivity versus two cases with 4% positivity, respectively. The reduction in Legionella colonization after copper-silver ionization was significant (P<.05) compared to the superheat and flush. Mean copper and silver ion concentrations (mg/L) were 0.29 and 0.054 from hot-water tanks, and 0.17 and 0.04 from distal outlets, respectively.


CONCLUSIONS
We conclude that a properly maintained and monitored copper-silver ionization system was more effective than the superheat-and-flush method for reducing the recovery of Legionella from the hospital water distribution system.
Stout
J E
JE
Special Pathogens Laboratory, Veterans' Affairs Pittsburgh Health Care System, University of Pittsburgh School of Medicine, PA 15240, USA.
Lin
Y S
YS
Goetz
A M
AM
Muder
R R
RR
D003300:Copper; D003428:Cross Infection / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D004203:Disinfection / Q000379:methods*; D006361:Heating; D006787:Hospitals, Veterans; D006801:Humans; D007231:Infant, Newborn; D017053:Infection Control / Q000379:methods; D007477:Ions; D016952:Legionella pneumophila / Q000254:growth & development*; D007877:Legionnaires' Disease / Q000453:epidemiology / Q000517:prevention & control* / Q000635:transmission; D008284:Maintenance and Engineering, Hospital / Q000379:methods*; D010414:Pennsylvania; D012189:Retrospective Studies; D012834:Silver; D014871:Water Microbiology; D014881:Water Supply
D007477:Ions; D012834:Silver; D003300:Copper