Isolation and characterization of a polyene-resistant variant of Candida tropicalis

Abstract

An atypical variant of C. tropicalis was recovered from multiple specimens from a patient who was a recipient of a bone marrow transplant. This yeast variant showed atypical morphology on corn meal agar distinguishable from typical isolates of C. tropicalis by the production of clusters of blastospores. Isolates of the variant produced acid, but no gas, from maltose and sucrose in fermentation tests. Isolates from blood, pleural fluid, respiratory secretions and stool specimens were susceptible to amphotericin B and nystatin in an agar dilution system. Isolates (8) of the variant C. tropicalis recovered over a period of 4 wk from the patient''s urine after amphotericin B therapy were resistant to amphotericin B and nystatin. The isolate recovered after 7 days of therapy had minimal inhibitory concentrations [MIC] of 100 .mu.g of amphotericin B and 20 .mu.g of nystatin/ml, whereas the 7 isolates recovered subsequently had MIC of greater than 500 .mu.g of amphotericin B and 50 .mu.g of nystatin/ml. The resistant isolates concomitantly lost the capacity to utilize amino acids that susceptible isolates could utilize. UV absorption spectra of non-saponifiable fractions of whole cells showed that resistant isolates lacked ergosterol, which susceptible isolates contained.