Copper and silver ions more effective against Legionellae than against mycobacteria in a hospital warm water system

• Published in: Water research (Oxford) Vol. 35; no. 17; pp. 4217 - 4225
• Main Authors: Kusnetsov, Jaana, Iivanainen, Eila, Elomaa, Nina, Zacheus, Outi, Martikainen, Pertti J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2001; Elsevier Science
• Subjects: antibacterial agents; Applied sciences; control; copper; Copper - chemistry; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Hospitals; Infection Control; ionisation; Ions; Legionella; Medical Waste; mycobacteria; Mycobacteriaceae; Pollution; Population Dynamics; prevention; silver; Silver - chemistry; Temperature; Waste Disposal, Fluid - methods; Water Microbiology; Water Purification - methods; Water treatment and pollution; ionisation; copper; silver; control; legionella; mycobacteria; prevention; Tap; Legionellaceae; Legionella; Silver Ions; Experimental study; Hot water; Microbiological control; Mycobacteriales; Copper Ions; Mycobacteriaceae; Bacteria; Actinomycetes; Hospital; Shower room; Hot water pipe
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(01)00124-5

We studied the influence of electrolytically released copper and silver ions on the microbiological quality in a warm water system of a hospital. The concentration of nontuberculous mycobacteria was followed for three, and that of legionellae and other heterotrophic bacteria in the water for four years. The highest concentrations of copper and silver ions were 220 and 68 μg/l, respectively. Silver ion concentration of about 3 μg/l was sufficient to control the growth of legionellae in circulating warm water. The results showed that it is more difficult to eradicate legionellae from taps and showers: these points were colonized by a small number of legionellae after the metal ion concentrations were increased in the circulating water. A regular use of water eradicated legionellae from the shower. One tap was still used irregularly, and this may be a reason why it still contained small concentrations of legionellae also in the last years of the study. Mycobacteria were occasionally isolated from the circulating water and repeatedly from the shower, even when the metal concentrations were high. To control legionella bacteria in warm water systems, silver concentrations of only 3 μg/l are needed if all taps and showers of the system are regularly used. Such low copper and silver concentrations, however, are not efficient against nontuberculous mycobacteria or other heterotrophic bacteria.