Second-step concentration of viruses in drinking and surface waters using polyethylene glycol hydroextraction

In our laboratory, virus adsorbed to talc--Celite layers is eluted with 100 mL of 10% fetal calf serum (FCS) in normal saline (pH 9.0). A further 10-fold reduction in the volume of the eluate was necessary before its inoculation into cell cultures. A 100-mL volume of an experimentally contaminated sample was placed in a dialysis sac and hydroextracted overnight (4 degrees C) with polyethylene glycol (PEG) 6000. The viscous material remaining in the sac was resuspended in 10 mL of Earle's balanced salt solution. After membrane filtration (0.2 micron), the concentrate was plaque assayed in BS-C-1 cells. Using this technique, recoveries of five laboratory-adapted enteric viruses (polio 1, echo 6, coxsackie B5, coxackie A9, and reo 3) and four freshly isolated enteric virus strains (polio 1, echo 1, coxsackie B3, and reo) ranged from 87 to 97%. In comparative tests, PEG hydroextraction was simpler and superior to organic flocculation.