Viability assessment by dye exclusion. A fluorescent method for fungal cells.

A new fluorescent staining technique for fungi utilizes the differential affinity of dead cells for rhodamine B. A mounting medium has been devised that includes the dye. This medium allows direct processing of cells from a broth and provides optimal conditions for fluorescence intensity. Comparison with the standard methylene blue exclusion test as applied to the Candida albicans yeast phase indicates similar specificity. Various pseudohyphae and several fungi also exhibited selective uptake of the dye when killed. This technique should prove useful in studying the effect of both drugs and cells on pathogenic yeasts.