Activity of voriconazole, itraconazole, fluconazole and amphotericin B in vitro against 1763 yeasts from 472 patients in the voriconazole phase III clinical studies

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Abstract

The susceptibility of 1763 yeast isolates (from 22 species and seven genera) was tested using Clinical and Laboratory Standards Institute M27-A2 microdilution methodology. Candida spp. predominated (97.1%), mainly C. albicans (51.4%), C. glabrata (16.4%) and C. tropicalis (13.7%), followed by Trichosporon spp. (1.1%) and Cryptococcus neoformans (1.0%). Most isolates came from blood/catheters (72.0%) or the oesophagus/oropharynx (11.3%). The voriconazole, itraconazole, fluconazole and amphotericin B MIC90 values (minimum inhibitory concentration for 90% of the isolates) for all isolates were 1.0, 2.0, 64 and 1.0 μg/mL, respectively. Voriconazole MICs correlated with those for fluconazole (r = 0.91) and itraconazole (r = 0.90). Only 109 isolates (6.2%) had voriconazole MICs ≥4.0 μg/mL; all were C. albicans, C. glabrata or C. tropicalis resistant to itraconazole (and most to fluconazole). Isolates from 22 patients with amphotericin MICs ≥2.0 μg/mL (range 2.0–16.0 μg/mL) were also cross-resistant to one or more of the triazoles. Patients (n = 34) with voriconazole-resistant isolates showed a 56% response to voriconazole therapy, and those patients (n = 261) with susceptible isolates showed a 71% response. Twenty-three voriconazole-treated patients had baseline resistant isolates, in eight patients voriconazole resistance developed during therapy and in three patients a different resistant species arose during therapy. Thus, voriconazole MICs correlate with those of fluconazole and itraconazole and may predict clinical outcome.

Keywords

Candida
Cryptococcus
Trichosporon
MIC
Clinical outcome

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