Classification of polyene antibiotics according to their synergistic effect in combination with bleomycin A2 or fusidic acid.

Five polyene antibiotics were compared for their effects on colony formation of either Chinese hamster V79 or Saccharomyces cerevisiae cells. A 10 to 40 times higher concentration of amphotericin B (heptaene) or nystatin (degenerated heptaene) was necessary to inhibit colony formation of hamster cells than that needed to inhibit colony formation of yeast cells. In contrast, colony formation of both hamster and yeast cells was inhibited to the same extent by similar concentrations of filipin (pentaene), pentamycin (pentaene), or pimaricin (tetraene). The five polyene antibiotics were also compared for their effects on colony formation of either V79 or S. cerevisiae cells when combined with a nonpolyene antibiotic, fusidic acid or bleomycin A2. Amphotericin B or nystatin could augment the cytocidal effect of fusidic acid but not that of bleomycin A2, whereas pentamycin or pimaricin could augment the cytocidal effect of both fusidic acid and bleomycin A2 against hamster and yeast cells. Filipin was found to enhance the action of fusidic acid and bleomycin upon growth of mammalian cells, whereas the pentaene polyene significantly potentiated the action of fusidic acid, but not that of bleomycin A2, against S. cerevisiae. It was therefore suggested that these polyene antibiotics be classified into two groups: group 1 (pimaricin, pentamycin, and filipin) and group 2 (amphotericin B and nystatin).