Rates of antifungal resistance among Spanish clinical isolates of Cryptococcus neoformans var. neoformans

Objectives: Activities in vitro of six antifungal agents were tested against a collection of 317 Cryptococcus neoformans var. neoformans clinical isolates. Methods: The procedure described in document 7.1 by the European Committee on Antibiotic Susceptibility Testing with minor modifications was employed. Results: Amphotericin B, itraconazole, voriconazole and ravuconazole exhibited a potent activity with geometric mean (GM) MICs under 0.26 mg/L. The GM MIC of flucytosine was 7.33 mg/L and that of fluconazole was 4.16 mg/L. The rates of antifungal resistance were 5.3% for amphotericin B, 0.9% for voriconazole and 3.1% for ravuconazole. Fifteen point eight per cent of strains had itraconazole MICs >= 1 mg/L, and 46% of strains had flucytosine MICs >= 8 mg/L. Fluconazole susceptibility (MIC <= 8 mg/L) stood at 53.4%. Conclusions: The percentage of fluconazole susceptibility was significantly lower than that in other surveys. Cross-resistance to itraconazole was common (33.8%) but almost the whole collection was susceptible to voriconazole and ravuconazole. These results should be confirmed with prospective and population-based surveillance programmes.