In vitro susceptibility of Candida species isolated from patients with haematological malignancies

Candida spp. (83 isolates including C. (Torulopsis) glabrata) were tested in vitro for their susceptibility to 5-fluorocytosine, amphotericin B, ketoconazole, itraconazole, fluconazole, and miconazole. The yeasts were isolated from clinical specimens, mostly from the lower respiratory tract, of 30 oncologic patients, 27/30 with haematological malignancies, during a 6-month period (December 1991-May 1992). Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) values of the 6 drugs were obtained for each yeast using a microdilution broth method developed in our laboratory. Amphotericin B, and 5-fluorocytosine were active against the majority of the yeasts with MIC90/MFC90 values within achievable serum concentrations (3.12/6.25 micrograms ml(-1) and 0.625/0.625 micrograms ml(-1) respectively). Azole derivatives showed a species-specific activity. MFC values were two to four times higher than those of the MICs, confirming the fungistatic rather than fungicidal activity of azole derivatives. An interesting correlation was found when the in vitro susceptibility values of the isolates were compared with data of patients with or without antifungal prophylaxis or therapy during that period. In general, with respect to fluconazole, C. albicans strains isolated from patients who received no treatment showed MIC and MFC values lower than those obtained from patients who were under prophylaxis or treatment with this drug. Fluconazole administration appears to influence in vitro susceptibility testing.