Susceptibility of clinical isolates of Candida lusitaniae to five systemic antifungal agents

Objectives: The aim of the present study was to expand the MIC database for Candida lusitaniae in order to further determine its antifungal susceptibility pattern. Methods: The activities of amphotericin B, fluconazole, itraconazole, voriconazole and flucytosine were determined in vitro against 80 clinical isolates of C. lusitaniae. A set of 59 clinical isolates of Candida albicans and of 51 isolates of Candida glabrata was included to compare the susceptibilities to amphotericin B. The MICs were determined by Etest with RPMI 1640 agar, and with both this medium and antibiotic medium 3 (AM3) agar for testing of amphotericin B. Results: All isolates were highly susceptible to fluconazole. The susceptibility to itraconazole was good; only 4% of isolates had dose-dependent susceptibility (MICs 0.25-0.5 mg/L). Voriconazole was very active in vitro (100% of isolates were inhibited at less than or equal to0.094 mg/L). Flucytosine MICs ranged widely (0.004->32 mg/L). The set included 19% of flucytosine-resistant isolates. For amphotericin B, 100% of isolates were inhibited at less than or equal to0.75 mg/L (MIC50 0.047 mg/L; MIC90 0.19 mg/L) and at less than or equal to4 mg/L (MIC50 0.25 mg/L; MIC90 0.75 mg/L) on RPMI and on AM3, respectively. A single isolate was categorized as resistant to amphotericin B (MIC 0.75 and 4 mg/L on RPMI and on AM3, respectively). Amphotericin B thus appeared very active in vitro against C. lusitaniae. Whatever the test medium, the level of susceptibility of C. lusitaniae to amphotericin B did not differ much from those of C. albicans and C. glabrata. Conclusion: C. lusitaniae appears to be susceptible to amphotericin B, azole antifungal agents, and, to a lesser extent, flucytosine.