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Clin Infect Dis. 1999 Dec;29(6):1507-11.

Four years of experience with silver-copper ionization for control of legionella in a german university hospital hot water plumbing system.

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Institut für Hygiene und Mikrobiologie, Abteilung für Hygiene, Sozial- und Umweltmedizin, RuhrUniversität Bochum, Universitätsstr. 44801 Bochum, Germany.


Silver-copper ionization was used for controlling Legionella distribution in a German university hospital hot water plumbing system for 4 years. In the beginning, silver concentrations were not allowed to exceed 10 microg/L because of drinking water regulation limits in Germany. Water samples were monitored for Legionella counts, temperature, and silver and copper concentrations. A significant (P<.001) 3.8-log reduction of Legionella counts, from 40, 000 cfu/L to 7 cfu/L, was found during the first year with silver-copper ionization. Nevertheless, the long-term efficacy of silver concentrations <10 ,++microg/L was not sufficient. Legionella counts increased to 10,000 cfu/L during the third year. During the fourth year, we studied the influence of higher silver concentrations on Legionella distribution. With an average silver level of 30 microg/L, only a 1.3-log reduction in Legionella, to 500 cfu/L, was achieved. The effect was not significant (P=.071); therefore, it must be considered that Legionella developed a tolerance to silver ions.

[Indexed for MEDLINE]

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