Combined effect of amphotericin B and flucytosine on hyphal growth of Candida albicans estimated at a single hypha level.

The in vitro efficacy of amphotericin B and flucytosine, separately and in combination, against the hyphal growth of Candida albicans was evaluated in situ using an automatic analysing system. A colony of C. albicans was in contact with a glucose-salt medium supplemented with biotin plus calf serum (GS medium) and GS medium containing the antifungal agent, in sequence. Minimum inhibitory concentrations at single hyphal level (S-MIC) were determined based on the response that was measured. Amphotericin B S-MICs ranged from 0.8 to 0.4 microgram ml-1, and S-MIC values > 102.4 micrograms ml-1 were obtained with flucytosine when the two agents were used independently. When the two agents were used in combination, however, a synergistic interaction between the two agents at concentrations below their individual S-MICs was observed.