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Effects of ionic strength on bacteriophage MS2 behavior: implications on the assessment of virus retention by ultrafiltration membranes

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  21st Century Watershed Technology: Improving Water Quality and Environment Conference Proceedings, 21-24 February 2010, Universidad EARTH, Costa Rica  701P0210cd.(doi:10.13031/2013.29417)
Authors:   Aurelie Furiga, Gwenaelle Pierre, Marie Glories, Pierre Aimar, Christine Roques, Christel Causserand, Mathieu Berge
Keywords:   Bacteriophage MS2, Ionic strength, Membrane filtration, qRT-PCR, PFU method

Bacteriophage MS2 is widely used as a surrogate to estimate pathogenic virus elimination by membrane filtration processes used in water treatment. Given that this water technology may be conducted with different types of waters, we focused on investigating the effects of ionic strength on MS2 behavior. For this, MS2 was analyzed suspended in solutions of various ionic strengths, firstly in a batch experiment and secondly during membrane ultrafiltration, and quantified using (i) quantitative RT-PCR (qRT-PCR), which detects the total number of viral genomes, (ii) qRT-PCR without the RNA extraction step, which reflects only particles with a broken capsid (free RNA), and (iii) the Plaque Forming Unit (PFU) method, which detects only infectious viruses. At the beginning of the batch experiments in solutions containing low amounts of salts, a loss of MS2 infectivity (90%) and broken particles (20%) were observed; these proportions did not change during filtration. In contrast, in high ionic strength solutions, bacteriophages kept their biological activity in static conditions but they quickly lost their infectivity during the filtration process. Increasing the ionic strength decreased both the inactivation and the capsid breakup in the feed suspension, and increased the loss of infectivity in filtration retentate, while the amount of MS2 genomes was identical in both experiments. In conclusion, ionic strength effects on MS2 behavior may significantly distort the results of membrane filtration processes and therefore the combination of classical and molecular methods used here is useful for an effective validation of the retention efficiency of ultrafiltration membranes.

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