Elimination of the yeast Candida parapsilosis from lymphoid cells and monolayer cells in culture.

In our laboratory, airborne yeast contaminants of cell cultures have consistently been of the genus Candida (species Candida parapsilosis), which are difficult to control with fungicidal agents. To salvage cell lines that show the presence of this fungus, two effective methods may be employed. In early stages of infection, the addition of activated mouse peritoneal macrophages (5 X 10(5) cells/ml) to the culture medium containing 5 micrograms Fungizone /ml eliminates all spores by phagocytosis. More heavily contaminated cultures can be depleted of fungi by density centrifugation on a layer of 38% Percoll. Remaining single spores, often not detectable by light microscopy, can be removed by the addition of macrophages (2 X 10(5)/ml) and Fungizone (5 micrograms/ml) to the culture medium. Contaminated monolayer cells can be freed of blastospores by several washes with balanced salt solution and subsequent culturing for 4 d in medium containing 10 micrograms Fungizone /ml without any toxic effects to the cells. These procedures can rescue valuable cell lines and hybridomas that would otherwise be lost.