Surveillance of triazole susceptibility of colonizing yeasts in patients with haematological malignancies

The species distribution and antifungal susceptibility of yeasts isolated from colonization cultures, and the contribution of previous fluconazole prophylaxis to the emergence of resistance, was prospectively studied in 87 neutropenic patients treated for haematological malignancies. Minimal inhibition concentrations (MICs) to fluconazole, itraconazole and voriconazole for 123 yeast isolates (65 Candida albicans, 22 Candida glabrata, 15 Saccharomyces cerevisiae, 5 Candida krusei, 5 Candida norvegensis, 11 other Candida spp.) were determined by E-test. Fluconazole MICs for Candida species and S. cerevisiae isolated from patients given prophylaxis were > or =2 mg/l in 24 of 40 (60%) isolates compared with 26 of 83 (31%) isolates from patients in the non-prophylaxis group (p =0.002). Among the non-albicans yeast species reduced susceptibility was common against itraconazole but was rarely found against voriconazole. Cross resistance between fluconazole and itraconazole was observed in 14 of all isolates, 4 of them also showing reduced susceptibility to voriconazole (MICs 4-8 mg/l). Fluconazole prophylaxis may contribute to emergence of less susceptible yeast strains also in patients with haematological malignancies not treated with allogeneic bone marrow transplantation.