Annulment of amphotericin B inhibition of Coccidioides immitis endospores. Effects on growth, respiration and morphogenesis.

Studies by others have shown that the growth-inhibiting properties of amphotericin B for susceptible fungi and yeasts are associated with the antibiotic's capacity to injure the organism's membrane. There is a resultant loss of stored metabolites from the cell. We have observed partial lysis of Coccidioides immitis endospores exposed for 24 hr. to 2·0 μg./ml. amphotericin B, which is consistent with findings on alteration of the membrane. Endospores so-treated do not grow. However, even after treatment with 4·0 μg./ml. of the antibiotic for 5 days, the capacity to grow is restored to the cells by furnishing them with approximately 0·6 mg./ml. cysteine or glutathione. These nutrients apparently do not react with the antibiotic per se but appear to nullify its effect by lowering the oxidation-reduction potential of the growth medium. In this regard amphotericin inhibition may also be overcome by evacuating air from flasks with antibiotic-containing medium. Relatedly, amphotericin-treated endospores do not s...