Persistence of bacteriophages in experimentally infected cell cultures.

A bacteriophage, isolated from a live measles vaccine and designated varphiV-1(L), was intentionally introduced into cell culture systems. The bacterial virus persisted in the cell cultures after daily medium changes and trypsinization, and in cell lysates prepared by freezing and thawing. The results suggest that phages contaminating cell cultures may be carried over into the final product during the manufacture of viral vaccines.