An automated radiometric microassay of fungal growth: quantitation of growth of T. mentagrophytes.

An automated radiometric microassay of the growth of Trichophyton mentagrophytes and other filamentous fungi is described. The assay is based upon the incorporation of 14C(U) glucose into the organism. Fractionation studies indicate that 73% of the label is found in trichloroacetic acid-insoluble macromolecular components of the mycelium. Incorporation of label directly correlated with growth as estimated by visual scoring of turbidity and as recorded in photomicrographs. Incorporation of 14C(U) glucose delineated a lag, exponential and stationary or plateau phase of growth. These phases could be completely inhibited by the antifungal agent tolnaftate. It was concluded that the growth of filamentous fungi can be successfully monitored by the radiometric method described. Moreover, this method is sensitive, accurate, reproducible, rapid and free of the variability inherent in many traditional estimates growth.