Comparative in vitro susceptibility of yeasts to amphotericin B and three methyl ester derivatives.

The in vitro antifungal activities of two N-aminoacyl derivatives of amphotericin B methyl ester (AME) were compared by tube dilution with those of amphotericin B and AME, using 60 isolates representing 10 yeast species. A total of 70% of the strains were inhibited by concentrations of the N-aminoacyl AME derivatives that were within a twofold dilution of the amphotericin B or AME minimum inhibitory concentration. The fungicidal activity of the N-aminoacyl AME derivatives was 3- to 16-fold lower than that of amphotericin B for 8 of 10 species. A considerable spectrum of antifungal activity was observed for N-aminoacyl derivatives of AME, which represents a new class of water-soluble polyene antibiotics.