The flow cytofluorometric susceptibility test (FCST) was incorporated into two in vitro synergy assays of amphotericin B-drug combinations. The FCST checkerboard assay and the FCST concentration-effect assay were developed to detect subtle modulation of amphotericin B fungicidal effects onCandida albicans andCryptococcus neoformans. Amphotericin B × cyclosporine A was a synergistic fungicidal combination against bothC. albicans andC. neoformans. Amphotericin B×gentamicin and amphotericin B×ketoconazole were synergistic combinations againstC. neoformans. In all cases tested, the synergy was effective when 0.50–0.62 μg amphotericin B/ml was used with>-0.50 μg of the other drug/ml. The fungicidal effect of ≥1.00 μg amphotericin B/ml overwhelmed the synergistic effects. A number of other drug combinations were additive, autonomous, or antagonistic.
KeywordsCyclosporine Synergistic Effect Gentamicin Amphotericin Ketoconazole
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