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Water Science & Technology Vol 54 No 3 pp 29–34 © IWA Publishing 2006 doi:10.2166/wst.2006.444

Accumulation of copper and silver onto cell body and its effect on the inactivation of Pseudomonas aeruginosa

M.G. Hwang, H. Katayama and S. Ohgaki

Department of Urban Engineering, the University of Tokyo, 3-1-7 Hongo Bunkyo, Tokyo, 133-8656, Japan (E-mail: mghwang@env.t.u-tokyo.ac.jp)


ABSTRACT

Pseudomonas aeruginosa, a gram-negative rod bacterium, is a causative agent of waterborne pneumonia and presents high tolerance against conventional disinfectants. The inorganic biocidal reagents, copper and silver, were applied to inactivate P. aeruginosa inoculated in a synthetic drinking water (SDW). Additionally, the relationship of the specific amount of accumulated copper and silver reagents (Cs) on P. aeruginosa with inactivation profile was elucidated in this study. Flow cytometry (FCM) following staining with SYTO 9 and PI was used for detection of bacterial viability and density. Individual copper and silver reagents, and their combination, exhibited excellent biocidal abilities even at the concentration of 0.05 mgCu/L and 0.005 mgAg/L. The critical amounts of accumulated disinfectant (Cs) were calculated at 2.82×10-7 mgCu/cellsi and 5.13×10-8 mgAg/cellsi at an incubation of 70 h. Consequently, the role of disinfectant on the inactivation of P. aeruginosa and the assessment of biocidal ability of copper, silver, and their combination were successfully explained by evaluating the terms Cs and Cc.

Keywords: Copper; flow cytometry; inactivation; Pseudomonas aeruginosa; silver


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