[Efficiency of current technics for the isolation of viruses in water]

In an attempt to evaluate the efficiency of the current methodology for the concentration of viruses from water and wastewater, we have determined the viral concentration in raw sewage using three procedures: a) inoculation of cell cultures directly with the filtered sewage, b) concentration of the viruses from the sewage using nitrocellulose filters at a pH of 3.5 in the presence of AlCl3, followed by elution with Nutrient Broth and inoculation of the cell cultures with the eluant and c) flocculation of the Nutrient Broth after the elution as in b, dissolution of the precipitate in cell medium and inoculation of the cell cultures with this solution. The results show that this concentration procedure with nitrocellulose filters as recommended in the "Standard Methods for the Examination of Water and Wastewater" has an efficiency of 33% if compared with the direct inoculation. In a separate study, we have looked at the properties of electropositive Filters to bind polioviruses Typ I, Strain Lsc 2ab at neutral pH in the absence of salt. These filters, which could be used several times, were able to retain more then 99.5% of the viruses. However, they bound the viruses stronger that nitrocellulose filters and the elution with Nutrient Broth was never complete. After the problems with the elution are solved, these filters promise to simplify substantially the procedure for concentrating viruses from water.