Studies of the effect of antifungal agcnts on a filamentous fungus by a biocell tracer system

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The biocell tracer system developped by Dr. Matsuoka is an apparatus to measure a hyphal growth. Using this apparatus, the effect of antifungal agents such as amphotericin B (AMPH), flucytosin (5-FC), miconazole (MCZ) and fluconazole (FLCZ) on hypae was studied. The bottom of culture vessel was coated with poly-L-lysine and 10^3 conidia of Aspergillus fumigatus were inoculated at the center of the vessel. Then liquid medium was poured into the vessel and the growth rate of a hypha adhering to the bottom was measured. When the growth rate dropped dto 0 after the addition of an antifungal agent, we judged the hyphal growth was completely inhibited. In particular this apparatus is very useful to study the synergistic effect of antifungal agents. The synergistic effect of AMPH and 5-FC was singnificantly influenced by timing of their addition to the culture vessel. When 250 mug/ml of 5-FC was used first into the medium and 2 mug/ml of AMPH was used 10 min later, the hyphal growth dropped immediately. However, when AMPH was added first and 5-FC was added 10 min later, the hyphal growth dropped gradually. When AMPH (2 mug/ml) and 5-FC (250 mug/ml) were used independently, no morphological changes of the fungal hyphae were observed. On the other hand, their combination at these concentrations showed a distinctinhibitory activity. This method is useful for antifungal activity testing of filamentous fungi.