Investigation of the value of β-glucan-specific fluorochromes for predicting the β-glucan content of the cell walls of zoopathogenic fungi

We have used the fluorescent dyes aniline blue and calcofluor white to stain the cell walls of a variety of pathogenic fungi, and compared our observations with the sensitivity of these species to inhibitors of polysaccharide biosynthesis. Calcofluor white, which interacts with 1,4-β-glucans such as chitin, chitosan and cellulose, induced fluorescence with all the fungi tested. However, aniline blue, which binds to 1,3-β-glucans, did not interact with Cryptococcus neoformans, Pityrosporum canis or Rhizopus oryzae. This apparent absence of 1,3-β-glucan correlates with the insensitivity of these three species to the antifungal echinocandin, an inhibitor of 1,3-β-glucan synthesis. Thus aniline blue and calcofluor white are useful agents for the study of the presence of β-glucans in the cell walls of pathogenic fungi.