A Modified Christensen's Urea and CLSI Broth Microdilution Method for Testing Susceptibilities of SixMalasseziaSpecies to Voriconazole, Itraconazole, and Ketoconazole

Abstract

Two supplemented broths (Christensen's urea with 0.1% Tween 80 and 0.5% Tween 40 and RPMI 1640 with 1% glycerol, 1% peptone, 1.8% glucose, and 0.05% Tween 80) were evaluated to determine voriconazole, itraconazole, and ketoconazole MICs for 200 Malassezia sp. isolates. Malassezia globosa and M. restricta were the least susceptible species (MICs at which 90% of the isolates tested were inhibited, 1 to >8 g/ml versus 0.25 to 1 g/ml).An increased incidence of severe dermatological and systemic infections by Malassezia spp. has been reported among immunosuppressed patients. Standardized assays are not available to determine the in vitro susceptibilities of these yeasts to any antifungal due to their complex nutritional requirements. Recently, Christensen's urea (measures metabolic activity) and supplemented RPMI 1640 (measures growth inhibition) broths were evaluated (16,21 pachydermatis).The 200 isolates were cultured from 77 patients (human immunodeficiency virus positive and negative) with dermatological pathologies (3) and 33 healthy volunteers. Isolates were identified by following conventional standard guidelines (10,11,15). Six reference Malassezia strains (see Table 2), CLSI quality control strain Candida krusei ATCC 6258 (2, 17), and Cryptococcus neoformans ATCC 90112 were tested as controls. The identification of representative isolates of each species and of the six reference isolates was confirmed by PCR-restriction fragment length polymorphism (8). For the quality control strain, the MICs of the three azoles were within the expected ranges (2, 17).CLSI RPMI 1640 medium (17)

Malassezia Species Associated With Dermatitis in Dogs and Their Antifungal Susceptibility

“…Furthermore, resistance by M. pachydermatis has been shown to develop in vitro with multiple passage at near MIC concentrations of antifungals, suggesting that the cellular machinery exists in this species for development of possible clinically relevant resistance. More resistant species reported are M. pachydermatis (Nakamura et al, 2000), M. furfur (Duarte et al, 2006), M. globosa and M. restricta (Rincon et al, 2006). Whereas M. sympodialis has been frequently found more susceptible to the tested antifungals (Miranda et al, 2007).…”

In Vitro Activity of E1210, a Novel Antifungal, against Clinically Important Yeasts and Molds

“…F. solani was subcultured on PDA and incubated at 35°C for 2 to 3 days and then at 25°C for 4 to 5 days. M. furfur was subcultured on modified Dixon's agar plates (3.6% malt extract, 0.6% peptone, 1.5% agar, 2% ox bile, 1% Tween 40, 0.2% glycerol, and 0.2% oleic acid) and incubated at 32°C for 3 days (21,27).…”

“…The medium for M. furfur was further supplemented with 1% glycerol, 1% peptone, 1.8% glucose, and 0.05% Tween 80 (modified RPMI 1640 medium) (21). The final concentrations of the antifungal agents studied ranged from 0.008 to 32 g/ml for E1210, 0.06 to 64 g/ml for fluconazole, 0.004 to 8 g/ml for itraconazole and voriconazole, 0.016 to 16 g/ml for amphotericin B, and 0.004 to 32 g/ml for micafungin.…”

Antifungal Susceptibility of Malassezia Species Isolated From Pityriasis Versicolor Cases

“…[4] The disease can be cured by using topical antifungal agents like ketoconazole and some patients who do not respond or experience multiple relapses may require systemic antifungal treatment with fluconazole or itraconazole. Hitherto, several methods are available for doing antifungal susceptibility of Malassezia spp in vitro [5][6][7][8][9][10] Only limited data was available on the susceptibility of Malassezia spp against topical imidazole and oral azole derivatives.…”