Synergistic action of amphotericin B and rifampin on Candida albicans

Amphotericin B and rifampin were tested for synergism against Candida albicans in a synthetic medium. The test was based on viability studies in which fungicidal activity was monitored during the first few hours of drug exposure. A fungistatic concentration of amphotericin B (0.1 μg per ml) in combination with an inactive concentration of rifampin (25 μg/ml) resulted in rapid loss of viability (kill > 99.9% in 8 hr). Rifampin alone at 50 μg/ml was inactive, and amphotericin B alone at 0.25 μg/ml was not as effective as the synergistic combination. Pretreatment of cells with amphotericin B did not render them susceptible to rifampin alone. On the basis of these and earlier studies, it is concluded that amphotericin B and rifampin are synergistic against various yeasts under widely differing experimental conditions.