Concentration of viruses in beef extract by flocculation with ammonium sulfate.

Bacteriophages and enteroviruses in water were adsorbed to positively charged filters (Virosorb 1MDS [AMF Cuno, Inc., Meriden, Conn.] or Seitz S [Republic Filters, Milldaler, Conn.]). Adsorbed viruses were eluted by treating the filters with 10% beef extract, pH 9. Organic flocculation of the beef extract at pH 3.5 permitted recovery of more than 40% of the enteroviruses tested but less than 15% of the bacteriophages present. A method was developed that uses salts at pH 7 to flocculate beef extract. Two volumes of saturated ammonium sulfate were added to beef extract, and both enteroviruses and bacteriophages were adsorbed to the flocs that formed. Greater than 70% of the enteroviruses and bacteriophages were recovered by centrifuging the sample and suspending the flocs in a small volume of distilled water.