In vitro antifungal susceptibility of Malassezia furfur from bloodstream infections

Abstract

Fungaemia caused by Malassezia spp. in hospitalized patients requires prompt and appropriate therapy, but standard methods for the definition of the in vitro antifungal susceptibility have not been established yet. In this study, the in vitro susceptibility of Malassezia furfur from bloodstream infections (BSIs) to amphotericin B (AMB), fluconazole (FLC), itraconazole (ITC), posaconazole (POS) and voriconazole (VRC) was assessed using the broth microdilution (BMD) method of the Clinical and Laboratory Standards Institute (CLSI) with different media such as modified Sabouraud dextrose broth (SDB), RPMI and Christensen's urea broth (CUB). Optimal broth media that allow sufficient growth of M. furfur, and produce reliable and reproducible MICs using the CLSI BMD protocol were assessed. Thirty-six M. furfur isolates collected from BSIs of patients before and during AMB therapy, and receiving FLC prophylaxis, were tested. A good growth of M. furfur was observed in RPMI, CUB and SDB at 32 6C for 48 and 72 h. No statistically significant differences were detected between the MIC values registered after 48 and 72 h incubation. ITC, POS and VRC displayed lower MICs than FLC and AMB. These last two antifungal drugs showed higher and lower MICs, respectively, when the isolates were tested in SDB. SDB is the only medium in which it is possible to detect isolates with high FLC MICs in patients receiving FLC prophylaxis. A large number of isolates showed high AMB MIC values regardless of the media used. In conclusion, SDB might be suitable to determine triazole susceptibility. However, the media, the drug formulation or the breakpoints herein applied might not be useful for assessing the AMB susceptibility of M. furfur from BSIs.

Malassezia infections with systemic involvement: Figures and facts

“…Regarding azoles, itraconazole, posaconazole and voriconazole seem to be very active, in vitro , against Malassezia ; conversely, fluconazole and ketoconazole exhibited a more inconsistent activity against these yeasts. The highest MIC values and widest MIC ranges were often observed with fluconazole, particularly when M. furfur isolates had been recovered from bloodstream infections in patients under fluconazole prophylaxis . In a recent study, ketoconazole exhibited low MIC values for most strains but very high MIC values for a few strains.…”

“…According to available data, Malassezia organisms exhibited conflicting results regarding susceptibility testing to amphotericin B: M. pachydermatis being inhibited by low concentrations of amphotericin B (≤1 μg/mL); and M. furfur and Malassezia globosa requiring high amphotericin B minimal inhibitory concentration (MIC) values . More often, reports described high MIC and wide MIC ranges depending on the strains tested . Regarding azoles, itraconazole, posaconazole and voriconazole seem to be very active, in vitro , against Malassezia ; conversely, fluconazole and ketoconazole exhibited a more inconsistent activity against these yeasts.…”

“…More often, reports described high MIC and wide MIC ranges depending on the strains tested . Regarding azoles, itraconazole, posaconazole and voriconazole seem to be very active, in vitro , against Malassezia ; conversely, fluconazole and ketoconazole exhibited a more inconsistent activity against these yeasts. The highest MIC values and widest MIC ranges were often observed with fluconazole, particularly when M. furfur isolates had been recovered from bloodstream infections in patients under fluconazole prophylaxis .…”

“…Several topical and systemic antifungal drugs are commonly used against Malassezia‐ related skin disorders . Because disease relapses are often found, a trend towards long‐term prescription of antifungals is increasingly reported and maintenance therapy is often encouraged in clinical guidelines .…”

Antifungal Susceptibility of Malassezia Species Isolated From Pityriasis Versicolor Cases

“…[20] M. globosa isolated from four PV cases and six cases of M. furfur showed highest MIC values at 16µg/mL for fluconazole. All these isolates belonged to chronic recurrent and extensive forms of PV.…”