title: Rapid, cultivation-independent assessment of microbial viability in drinking water.
abstract: Fast and accurate monitoring of chemical and microbiological parameters in drinking water is essential to safeguard the consumer and to improve the understanding of treatment and distribution systems. However, most water utilities and drinking water guidelines still rely solely on time-requiring heterotrophic plate counts (HPC) and plating for faecal indicator bacteria as regular microbiological control parameters. The recent development of relative simple bench-top flow cytometers has made rapid and quantitative analysis of cultivation-independent microbial parameters more feasible than ever before. Here we present a study using a combination of cultivation-independent methods including fluorescence staining (for membrane integrity, membrane potential and esterase activity) combined with flow cytometry and total adenosine tri-phosphate (ATP) measurements, to assess microbial viability in drinking water. We have applied the methods to different drinking water samples including non-chlorinated household tap water, untreated natural spring water, and commercially available bottled water. We conclude that the esterase-positive cell fraction, the total ATP values and the high nucleic acid (HNA) bacterial fraction (from SYBR Green I staining) were most representative of the active/viable population in all of the water samples. These rapid methods present an alternative way to assess the general microbial quality of drinking water as well as specific events that can occur during treatment and distribution, with equal application possibilities in research and routine analysis.
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, P.O. Box 611, CH-8600 Dübendorf, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Berney
authors.forename: Marius
authors.initials: M
authors.lastname: Vital
authors.forename: Iris
authors.initials: I
authors.lastname: Hülshoff
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Weilenmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Egli
authors.forename: Frederik
authors.initials: F
authors.lastname: Hammes
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001431:Bacteriological Techniques; D052160:Benzothiazoles; D015169:Colony Count, Microbial; D003959:Diamines; D005434:Flow Cytometry; D009930:Organic Chemicals; D011804:Quinolines; D013194:Staining and Labeling; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods; D014881:Water Supply
chemical_list: D052160:Benzothiazoles; D003959:Diamines; D009930:Organic Chemicals; D011804:Quinolines; C098022:SYBR Green I