Amphotericin B tolerance: a characteristic of Candida parapsilosis not shared by other Candida species

Thirty yeast isolates from clinical specimens were tested for their susceptibility to amphotericin B at 30 C, 37 C, and 39 C. Of the six Candida albicans, five Candida tropicalis, one Candida guilliermondii, one Candida krusei, one Candida pseudotropicalis, two Torulopsis glabrata, and four Cryptococcus neoformans isolates tested, all were inhibited at amphotericin B concentrations of less than or equal to 0.4 micrograms/ml and killed by concentrations of amphotericin B that were less than or equal to 16-fold higher than the minimal inhibitory concentration (MIC). Although growth of Candida parapsilosis was also inhibited by concentrations of amphotericin B of less than or equal to 0.4 micrograms/ml, minimal fungicidal concentrations of amphotericin B were greater than or equal to 32-fold higher than MICs for each of the 10 isolates examined. This unique susceptibility pattern of C. parapsilosis resembles the antibiotic tolerance observed with Staphylococcus aureus. Variations in temperature within the experimental range did not affect the amphotericin B susceptibility for any of the yeasts examined.