Four years of experience with silver-copper ionization for control of legionella in a german university hospital hot water plumbing system.
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.
Rohr
U
U
Institut für Hygiene und Mikrobiologie, Abteilung für Hygiene, Sozial- und Umweltmedizin, RuhrUniversität Bochum, Universitätsstr. 44801 Bochum, Germany. rohr@hygiene.ruhr-uni-bochum.de.
Senger
M
M
Selenka
F
F
Turley
R
R
Wilhelm
M
M
D002713:Chlorine / Q000494:pharmacology; D015169:Colony Count, Microbial; D003300:Copper / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D005858:Germany; D006785:Hospitals, University; D006801:Humans; D017053:Infection Control / Q000379:methods; D016952:Legionella pneumophila / Q000187:drug effects*; D007877:Legionnaires' Disease / Q000517:prevention & control*; D015999:Multivariate Analysis; D012834:Silver / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors; D014871:Water Microbiology; D014881:Water Supply
D012834:Silver; D002713:Chlorine; D003300:Copper